Computer Monitor RepairUpdated November 11, 2003

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QUESTION NO. P101503-4:  Acana Peripherals 17s monitor FCC IIB-UA1.  I need the value of burned R472, R473, R492, R493 and R495. In the TVM schematic, I read R472 as 1K; R473 as 20K; R492 as 1M; R493 as 51K; and R495 as 10K. But these likely died from a bad flyback, T404, which would need replacing. 

 

QUESTION NO. P101503-8:  Dell 1028L monitor.  What is the value of the ph-33d?  Without the component's chassis location number, the service literature cannot be referenced, but this may be a Philips fast-recovery type rectifier, BYD-33D, rated 200 Volts, 1 Amp. Possible substitutes for that one, are FR103, NTE552, or NTE574.

 

QUESTION NO. P100603-2:  Viewsonic E70,  burnt R457 resistor, next FBT. Need the value of resistor. Caused by s/c c445 connected to collector of FB transistor Q407.  There are many different Viewsonic E70 models, so without the 'VCDTS' model number, one cannot be sure which one is your model. However, the E70-3 version does have its R457 connected to the collector of Q407 via a capacitor (the other end of R457 goes to the base of PNP Q426, in that E70 version), and in that chassis, R457 is 1.5K Ohms, 1/2 Watt.

 

QUESTION NO. P100103-7:  HP D2817A monitor.  I need the value of R612 (surface mount resistor at the bottom of the PCB).  R612 is 270K Ohms; its size is larger than most SMD, could be a 2010 size (1/2 Watt).

 

QUESTION NO. P082703-4:  LG Studioworks 99T monitor, Q520 is fried. Part reads K2379, seems to be Sanyos mosfet 2SK2379.  Part is impossible to get in Germany, are there any equivalent replacements? Although Sanyo's 2SK2379 is a logic-level gate Mosfet, in the LG 99T circuit, Q520's gate is driven by a 12 Volt source, so a standard-gate Mosfet like Fairchild's IRFS650B or SSS45N20B (or SSP45N20B with an insulator) might substitute for 2SK2379 in this location.

 

QUESTION NO. P092503-10:  evokd1730 (Vs-7) monitor.  I need reference Q 411. Q411 is BU2525AF.

 

QUESTION NO. P082503-2:  DA-456 CRT Monitor.  I need the values of D406, R475 and R471.  D406=1N4148, R475=10Kohm 1/4W, R471=30Kohm 1/4W

 

QUESTION NO. P090403-6:  Viewsonic G810 VCDTS 23852-6M monitor, horizontal scan is missing on the right side.  There is distortion of the scanning lines before they peter out.  If there is a bad blanking pulse at pin 17 of IC601, on the CRT board, one possible way to restore the blanking pulse, is to change the value of R460 (100K) to 15K Ohms, to increase the base drive for Q4412.

 

QUESTION NO. P081803-10:  LKOM L705 monitor is dead, power supply working, the led is on but no EHT.  Collector has 50 volts of HOT transistor but no signal on base of the transistor. The chip is TDA9115 but no output at vertical and horizontal output sections.  .50V on the collector of the transistor is ok but if the base does not have it to turn it on the transistor will not conduct or turn on and that 50V will not go to ground or its proper place.  As for TDA9115 no output [check for the correct voltage, ground, input to the unit].  Maybe something is loading the output of the TDA9115 down.  If disconnect the output and check it again.

 

QUESTION NO. P090303-5:  Acer 7276e monitor FCC JVP7276E.  I need the value of C326 by the HOT and value and location of FR101.  I was told to also check F701, F702, F703, F704, J013, R326, R328, R241, R329, C327, C304, D308, L304, ZD210, IC201, Q301, Q302, and Q316. The Acer 7276e schematic shows C326 as 270 pF/500V. FR101 (2A) is on the CRT board, on the +85V line, located between pin 4 of the 5-pin plug M103, and C170.

 

QUESTION NO. P090303-3:  KDS monitor FCC EVOKD-1910T, what is the part number for the FBT?  In a KDS AV-195T with this FCC number, KDS used FBT type Y265432B. Also, H.R. Diemen claims that their FBT type HR46206 is a replacement for Y265432B.

 

QUESTION NO. P082803-5:  Nec MULTISYNC 95F monitor is missing R31A, I need the value.  Assuming this NEC is chassis N9902, R31A appears to be 0.33 Ohm, 1 Watt, fusible.

 

QUESTION NO. P082703-7:  Acer 7178ie monitor FCC JVP7178ie. Arcing or sparking at the neck board between ground to either F1 or F2. The flyback has 4 wires output, one is High voltage, G2, the other two wires just guessing are either F1 and F2. Is the flyback (# TLF 063-11-39) defective?Yes, arcing at the focus pins is a common fault from a defective 7178ie flyback. The Acer number for this flyback is 19.70033.011. The TLF063-11-39 is not the actual flyback number, that number is just for the focus pack.

 

QUESTION NO. P082503-4:  Compaq V90 monitor FCC BR8SM-994.  I need the value of burned R866.R866 is 2.2 ohms, flameproof.

 

QUESTION NO. P082503-5:  Samsung45bn monitor has a white screen but no picture.  Checked the HOT, the two 220 diodes are ok.  All main diodes are fine.  Did in circuit testing of all small transistors, they show no shorts.  Checked 53 volts 70 volt and 12 volt they are fine.  The hot heatsink heats abnormally, nothing else heats up or blows.  Switching on function is normal, I can hear is degauss and then back, the led also stays green.I replaced 1rf 630 near the buttons and it fixed the problem.

 

QUESTION NO. P082203-4:  Proview 986M monitor  FCC IJE986.  What are the values of Q663 and Q664?  The board is version  200-100-PR98E rev: F3+.  Q663 and Q664 are shown as being either KSC5042F, or 2SC4686A, in the schematic. Possible alternatives are 2SC4630, or a 2SC3675 with insulator hardware added. B&D Enterprises (ww.bdent.com) is one source for these transistors.

 

QUESTION NO. P082203-3:  LG Flatron 775FT monitor.  I need the equivalent for FJAF6812 horizontal transistor.   Possible substitutes for FJAF6812 include 2SC4890, 2SC5411, BU4525AX, and NTE2365 with an insulator.

 

QUESTION NO. P082103-4:  Sony/Sun gdm 20e20 monitor has a flickering picture, not horizontally centered and unstable vertically in a jumping back and forth fashion.  All voltages are ok and no damage to pcbs can be found.  These sort of faults can be caused by a defective IC007 = CXA1908S, Sony p/n# 8-752-076-34, on the "D" board. Often, replacing this IC then requires DAS software re-alignment of the screen geometry parameters.

 

QUESTION NO. P081803-9:  Samsung Sync Master 753S & 750s monitor.  I need the part number of the FBT. For Samsung chassis DP17L, two FBT's are listed, FEA831 (BH26-00035A), or FQB17A001 (BH26-00026A).  FEA831 and FQB17A001 should be similar, or the same, for they cross to the same HR Diemen equivalent, HR46203. For Samsung chassis AQ17LS, the FBT is listed as LCE-CF1781, Samsung part code BH26-00109A.

 

QUESTION NO. P71103-4:  NEC V520(B) monitor without FCC #.  The power is ok and LED indicate green but no display.  No HV and relay does not click.  Checked HOT it's ok.  Checked all resistors, diodes and transistors at power supply and deflection area and looks all ok.  Try resoldering  tube connections, especially G2.

 

QUESTION NO. P72503-1:  Optiquest V95 Model vcdts2183 monitor FCC GSS1900 the horizontal sync is way out, the picture is only 4 inches wide.  I think LM1292N IC is bad but can't locate one. I used to purchase IC's from LJ but his site is no longer there. LJ Enterprises' new web address www.ljecc.com/

 

QUESTION NO. P70803-3:  Sony CPD-E220 monitor power supply and HV are ok but low G2 and switches on with signal then shuts down after 30 seconds steady orange flashing led.These units are lemons.  Sony will replace between certain serial numbers because they cannot supply eeproms & microprocessors.  Do not try to fit blank eeprom or it will blow in a big way.

 

QUESTION NO. P73103-6:  Sampo km718dt monitor chassis c718.  I need values of R509 and C503.  In my Sampo KM-718 manual, R509 is 22 Ohms, 2 Watts, and C503 is 0.047 uF, 400V.

 

QUESTION NO. P72903-9:  KDS monitor FCC EVOKD-1910T.  I need substitute part for transistor A1281 at location Q818.  A possible substitute could be Fairchild's FPN660, but its pinout is EBC, instead of ECB, so its leads would need to be inserted correspondingly. Mouser Electronics (www.mouser.com) is listing FPN660.

 

QUESTION NO. P72103-10:  NEC multisync FE700+ monitor, all digital alignment controls work except width and pincushion.  If problem is processor please mention source for same.  In many digital monitor it happens that there width and pincushion control doesn't work other all controller functioning ok. This problem is due to the Transistor which control the Horizontal Size. mostly it is located on the

center of the circuit board. Look for the Transistor B649A and replace it. Some time there are more then one so if there are then check them all and replace the defective one.

 

QUESTION NO. P72103-9:  KDS Multiscan color monitor FCC EVOKD-1910. is dead, components are burnt.  I need the value and part numbers of Q424, Q818, IC 403, R424, R466, R468, R462.  I have EVOKD-1910T here, I think it is quite similar so I'll try to help a bit.  Q424 is 400V N-Channel MOSFET IRFS730, IC403 is SMPS Controller KA3842B (the same as IC404 you have there), R424 is 3600 ohm, R468 is 1 ohm. Have you check yr flyback? I could not locate Q818 (Q810?). My R466 and R462 are burnt too, waiting others to help.  R466=1k ohms 1/4w R462=10  ohms1/4w.

 

QUESTION NO. P72903-8:  HP M70 D5259A monitor, chassis D5259-60050, I need value R451  HP has installed several different chassis in model D5259A, but if yours is a Tatung C7B chassis, the schematic for the Tatung C7B shows R451 as 1.5K ohms.

 

QUESTION NO. P72503-7:  Viewsonic P810 monitor is dead.  I replaced a shorted horiz. output transistor.  It is still dead but now there is a ticking noise from the power supply.  Viewsonic has made several different versions of P810, with different FCC and VCDTS numbers, so specific tips cannot be given. However, in general, when HOT's short in these, the B+ regulator FET (usually a P-channel FET) is also bad. Sometimes also, the damper diode, and/or diodes on the SMPS secondary 200 Volt rail, are bad, or fuses or fusible resistors in the B+ supply line are open. Also check the base drive circuit components for that shorted HOT. In some models, bad FBT's are common.

 

QUESTION NO. P72803-3:  Viewsonic G790 model VCDTS21385-1M monitor.  Initial fault was arcing on the FBT.  I replaced it (FEA661). No arcing but no operation either.  Q303 (2SC5331) and Q103 ( IRF740) were shorted.  Q303 is the HOT ;Q103 is a regulator in the HV circuit.  Replaced both and tested again.  Q303 shorted again but not Q103.  The HVOPT (Q105,  C5124) never blows. Q601 (the B+ regulator in the HOT circuit) was tested OK but replaced anyway. Also tested damper diode D304,  D317,  and R334.  What is causing Q303 to short?  I have located the culprit.  It was D123 (shorted) in the G1 circuit output of the FBT.  It looks like the load on the HVOP was causing the B+ on the HOT to wildly fluctuate and take out the HOT.

 

QUESTION NO. P72503-3:  Apple M6496 Studio Display monitor no FCC or model number, made by LG Electronics.  There is no B-plus to the horizontal output transistor, Q707.  I have carefully checked the board with a magnifying glass. Check that B+ voltage passes through P-FET regulator Q404. Also check C411, ultrafast D405, and damper D714. If there are no pulses on the gate of Q404, check R439, zener D404 (18V), and ascertain that horizontal drive is being

provided to Q404's gate from IC701.

 

QUESTION NO. P72503-5:  HP D2837 monitor, when the power is turned on, the unit draws 50 watts constant, the raster pulsates about 4 times per second.  The pulsating starts in the center and expands outward about 1/2 inch both horizontally and vertically.  The B plus voltage holds steady at 88 volts.  The High Voltage "vibrates" at 27.5  Assuming this HP model is FCC#A3LCKB722, I would check C517 (3.3 uF, bipolar); the schematic lists it as 50V, but sometimes the manufacturer has skimped on this one's voltage rating. If C517 is OK, then check the flyback.

 

QUESTION NO. P72303-10:  AOC monitor spectrum 4v has power green led but has no display. Check diode near power supply, damper diode (her 303,stpr 303).

 

QUESTION NO. P72403-3:  Dell p991 19 Sony monitor,  I am measuring 30 KV for high voltage and unless I lower brightness and contrast  down to 30% of full the monitor goes into shutdown.  How can I lower HiV to 26-27 KV?  When I pull crt socket off the tube all is OK, so I'm guessing its excessive beam current.  According to the manual, HV is adjusted to 27KV by RV901 (on D board, under a cover and RTV silicone). Also, check components in the HV regulatory circuit (R924, R925, RV901, IC901, and FBT T901), and the HV and ABL protection circuits (R917, R918, R920, R921, R923, R932, R933, R191, R1004, R1006, C920, D911, D912, D915, D917, IC901, T901), in case any are off-value or faulty. Note, Defective FBT's (Sony p/n# 1-453-317-11) are one cause of 30KV HV in this model.

 

QUESTION NO. P72403-9:  Samtron SC 726GXL monitor FCC A3LCMH737.  I need value of C506  According to the SC-726GXL manual, C506 is a metallized polypropylene film capacitor, 0.33 UF, 400 Volts, 5% tolerance.

 

QUESTION NO. P72303-3:  Proview px561 monitor.  I need the reference of the transistor Q630 . Q630 is IRF634, or an equivalent type. IRF740A can also substitute. If Q630 is bad, also replace C635, and carefully check D632 for reverse leakiness.

 

QUESTION NO. P72203-5:  Compaq MV520 monitor displays bad horizontal width problems. Can adjust vertical ok using setup adjustment controls but not horizontal width or position. I have changed IC U401 and U2. Compaq MV520 has several chassis versions, with different CO-xxxxx model codes, but if your version has a dual diode at D801, check it for bad solder, and for reverse leakiness in the diodes. If D801 has problems, also check FET's Q802 and Q805, in case D801 has damaged them.

 

QUESTION NO. P70803-9:  Philips 107E20/00Z monitor, I need type of power mosfet in power supply section part number 7101. It is some ST microelectronics type but cannot read because burnt badly. The original part is SSP7N60A. A substitute part is IRFB9N60A. The Philips part number is 9322 135 00687.

 

QUESTION NO. P72103-1:  Dell GDM-5001PT monitor does not respond to the controls for vertical center and vertical size, also has pincushion on both sides.  How do I reset ic007 in the D board, CXA-2043Q like Samsung TV's? This Dell is a Sony, not a Samsung, chassis. The symptoms sound more like a defective IC007, than one that needs realigning via Sony DAS software. If you replace IC007, beware of lifting the fine PCB traces. Sony distributors have CXA2043Q, as Sony part number 8-752-078-46, or MCM Electronics may have the generic part available.

 

QUESTION NO. P71703-4:  Compaq 150 Model 445A monitor, Chassis CM0200, FCC A3KM050. Phillips Manufactured, but no help there. Of course Compaq recommends replacement. R3423, R3424, R3426 burned. Need values. Vertical IC shorted after powering it up with the cable connecting the mask to the CRT Board unhooked. (Looking for loose solder connections). Anything else I should be looking at? Vert IC replaced, of course. In my Philips manual for CM0200, R3423 is 220 ohm, 0.33 Watt; and both R3424 and R3426 are 4.7 ohm, 0.5 Watt.

 

QUESTION NO. P71503-1:  Viewsonic GS815 monitor, I need the part number of the vertical IC. The vertical IC is TDA8172; also check nearby electrolytic capacitors for  possible damage from incorrect supply voltages. 

 

QUESTION NO. P71003-7:  LG Studioworks 74m monitor, FCC BEJCM710.  Initial problem was no go with ticking sound.  Checked H.O.T which was ok.  Replaced Flyback Transformer, and monitor now operates BUT only when the video cable is not plugged into the rear of the monitor.  As soon as I plug the cable in the monitor goes into standby mode, and B+ goes high. Check the B+ coil and capacitors, coil is to left of fbt near p/supply inspect closely for burning and test value, check the fet also. Every now and then one of these will do more damage when the fbt goes, some only the fbt.

 

QUESTION NO. P71003-8:  Samsung 550S (DP15LS) monitor, I cannot adjust the colors, no screen pots(red, blue, green), no driver pots, no DAS connectors. Color adjustments on the DP15LS model are done with Samsung's Softjig software, and the Samsung Softjig interface assembly (interface board Ver. 2.0, and signal cable).

 

QUESTION NO. P71003-4:  HP D2825 monitor FCC 7154E.  Display was split into two parts horizontally and about 3inch diagonal bar was in the center of the screen. I checked H stage.  I changed H.O.T (BU2520AF), now Q317 N CHANNAL F.E.T (K2161) is blowing.  I replaced it with IRF 740 but, its also over heats & seams to be burned. Also need value of zener diode D316.  Another problem is when connect the Vga cable, the front panel controls does not  work. When Vga cable is disconnected the front panel controls (Bright, Contrast, Size, etc) work.  First change ceramic cap C335 (220pF/2KV), by the flyback. If R214 (15K) is bad, IC201 (TDA4858) is probably also bad. Since Q317 repeatedly burns, also check if coil L304 has burnt or shorted windings, or has lost inductance (L304 should retain at least 0.7 mH in inductance), and check zener D316 (24V), ultrafast diode D317, and C326. 

 

QUESTION NO. P71003-3:  Compaq mv520 monitor has 240 volts (Australia) in to board power supply but nothing else to the rest of the board, front led flashes dimly.Replace Q505 (IRF630) FET mounted on FBT cage. Dry joints on FBT and C513 (100uF200V) swollen. But any heavy drain on the supply could cause this.

 

QUESTION NO. P70903-4:  Dell P1110 monitor, G2 dies out after 1 to 2 hours, spraying coolant on Q406 brings back the picture.  Q406 is surface mounted with no visible markings, what is the generic part #? In the Sony Manual, Q406 is either a Matsushita 2SB709A (in the schematic), or a Toshiba 2SA1162 (in the parts list); these two PNP transistors have similar specs. The parts list shows Q406 as 2SA1162-G (G = gain bracket 200-400), and Sony p/n# 8-729-216-22.

 

QUESTION NO. P70903-5: Digital CMC-1511BW/SM monitor Chassis CMC-1509B was dead.  Replaced damaged transistor (FET) 2sj449 (part #Q133) and main H-Out transistor 2sc4924 (part #q500).  Now monitor is on but is not showing any picture signal coming from the VGA of the computer.  I checked the vga with another monitor which worked fine.  In the standby mode some tick tick sound coming from the relays RL501 and RL503 near the H-Out transistor and in full working mode the noise coming from the flyback or near around the flyback.  With Q133 and Q500 bad, I would also check R150 (10 ohm); C539; ultrafast rectifier D132; and the rectifier for the 200V secondary supply off the SMPS transformer.

 

QUESTION NO. P70803-10:  Tatung C7BZR monitor.  I need a substitute for a dmv-32 or dmv-56. Its a damper/modulation diode pack in a transistor case. Possible substitutes for ST Micro's diodes DMV32B and DMV56 include Sanken's types FMP-2FUR, FMQ-2FUR, FMT-2FUR; also, Fairchild's type FFPF60B150DS. DMV32B diode is available in UK from http://www.dalbani.co.uk/index.php

 

QUESTION NO. P70703-4:  IBM 6556-03N monitor Sony chassis SCC-LO7G-A   raster is tearing top 1/3 of screen, improves as it warms up.  Worse in high resolution modes. Check C575; also check C573, since the problem is worse in certain modes.

 

QUESTION NO. P70703-2:  AOC 7klr monitor.  Need value of r626, burnt beyond recognition. Value of R626 is 820E 1w.  After replacing screen shows thin lines and foldover on top.  Changed TDA 4866 and electrolytics around this IC.  Fixed the problem.

 

QUESTION NO. P62303-10:  Kimodo K7 Sceptre monitor is dead after not being used for three months.  No known damage nor surges. PLED blinks short on, long off. Next time include size, proper make, model, year, FCC ID, UL and CSA.  Your unit is a 17" Komodo (Sceptre) computer monitor model P773, part number:K73P, year:  March 10,1999, FCC GKRM773,UL:1K97.  Your unit like 70% of all of those chassis have a defective T802=FEA632 (Sampo)=flyback which takes out the HOT,Q503=2SC5387 which could be subbed for ST2408HI,BUH1015HI,BU2508AF or 2SC3886./

 

QUESTION NO. P60503-1:  Compaq mv520 monitor.  What is the correct line output transistor fitted to this chassis? Line output transistor is BU4508AX

 

QUESTION NO. P52903-7:  AppleVision 850 Monitor was originally intermittent, when display would disappear. This seemed to be a heat-related problem, as monitor would power up normally after letting it stand for some time.  Disassembled monitor, and resoldered some suspect joints. This fixed the intermittent problem. Monitor then lost display, with no obvious signs of overheated components.  Now when powered up, and video signal asserted from computer, power LED blinks ORANGE at about 2Hz. Are there any points where critical DC voltages can be checked? Check vertical IC and caps.  If I remember correctly pins 6 & 7 or pins 5 & 7 will short.

 

QUESTION NO. P61903-10:  Apple Multiple Scan M2494 FCC AK8M2494.  About 10 ~13 seconds after turning on the unit, picture gets so bright (with retrace lines) causing the unit to shut down. All main voltages test ok;  G2 voltage is about 1kv at the source, but seems to have an automatic G2 regulation circuit at the CRT module.Check tube socket connections for dry joints.  These units lift smd components on video board near the heat sink component side.  Also check microprocessor output.

 

QUESTION NO. P61703-2:  Dell D1626HT monitor (Sony chassis SCC-L04K-A) with no red color. After check and replace de IC403 (FA4111) without result, I think the problem can be caused by malfunction of IC402 (M52722P).  I haven't any datasheet of M52722P and I can't find in Mitsubishi Semiconductor site.  In the schematic, the Red input to IC402 is to pin 17, and is about 2.8V. Red drive (pin 18) is about 3.9V, Red hold (pin 35) is about 4.4V, and Red Output (pin 37) is about 2.7V. Vcc for red (12VDC) is IC402, pins 16 and 36; red ground pins are pins 24 and 29. Red output goes to transistor Q101 (PNP, base is about 2.8V, emitter is about 3.5V),

then continues on to input at IC403. If another IC is needed, IC402 (M52722P) is Sony part number 8-759-468-63.

 

QUESTION NO. P61703-3:  Nokia 447x258 monitor.  Need part number for T27 FET. T27 is IRF9622, a P-channel Mosfet; an IRF9620 could substitute.

 

QUESTION NO. P61703-5:  Acer 7156e monitor, JVP7156E totally dead.  Checked all resistors, transistors, diodes and caps in primary side.  Replaced ic uc3842 but did not help.  When switched ON, main capacitor still holds current.  Double checked all component in primary and secondary.Unfortunately in this monitor a charged cap does not mean much. The main drive is not the IC you changed but IC701 via an opto coupler so if there is a short say on the flyback IC701 will lock down and C612 will be fully charged. I then suggest check the usual output transistor etc and ring the flyback if you can.

 

QUESTION NO. P60903-2:  Hyundai S560 monitor has narrow screen.  I need the value of burned Q312, I can make out K D2. Q312 is D2061

 

QUESTION NO. P60603-3:  Samtron 750S or 753S monitor with Eprom IC 24C04, first MENU never use to come when I replaced 24C04 (ST make China) first instant it worked correct, but after switch on again the width becomes less, I tried with next IC, again the same thing, I tried with 24C08 of other make same thing again. After replacing the eeprom you need to do an alignment with Samsung's Softjig software and interface. After doing the alignment, save the data to the eeprom.

 

QUESTION NO. P61203-9:  Samsung Syncmaster 15GLI monitor.  I need values of R609, R610, R616 & zener diode D610.  R609=0.18ohm 1W, R610=1K ohm 1/6W, R616=15K ohm 1/2W, D610 = 16V zener( UZ-16BM).

 

QUESTION NO. P61203-8:  Compaq V75 model 623T monitor.  I replaced FBT (FEA662), Q831 (BU2520?), R866 (2.2 Ohm 1/4W). I want to be sure about Q831, is it supposed to be a BU2520DF (with damper diode) or BU2520AF (without damper diode)? The version of BU2520 used for Q831 is BU2520DF (contains a damper).

 

QUESTION NO. P61203-10:  HP D5259A monitor Chassis C-711 has a horizontal line across the screen. 

Resoldered cracked solder joints at I602 (vertical IC), still horizontal line.  R618 is fried, what is its? R618 is 1 ohm.  Also check if the vertical chip is damaged.

 

QUESTION NO. P61203-2:  Philips 107e monitor, power supply contains smps  ic which is TEA1504.  I need a replacement from other manufacturers. That is a specialized chip made by Philips so forget about other makers.

 

QUESTION NO. P60503-8:  NEC P1250 monitor with vertical field collapse. i.e. a horizontal line is visible in the center of the screen.  I have replaced the IC104 but the problem remains. No vertical deflection has a specific troubleshooting procedure.  1st. Check vertical yoke winding connections on PCB and measure.  resistance of winding with yoke unhooked from PCB (expect 8.2-11 ohms).  2nd.  Locate B+ pin of Vertical Output IC and check for DC voltage typical 25-27VDC.  3rd.  Locate vertical sync input pin of OUTPUT IC and check for sync in lack of sync means VERTICAL drive missing from further back in circuit typical cause is 2.2 uf cap @50 vdc series coupling.  4th.  Look for a 100uf cap at cathode of B+in diode negative will go to pin labeled PUMP or RAMP if this cap has low ESR no vertical defl will occur and output DC reference voltage will be 50-70% of documented value.  5th. Some vertical circuits use a series defl cap in the range of 1000-3300 UF.  if this cap is open no deflection will occur. Other variations use less than 1 ohm resistors from NEGATIVE of this cap to ground. Poor solder (heat stress) oropen resistors take cp out of return line and thus NO DEFLECTION.

 

QUESTION NO. P61003-10:  Proline 7G1r monitor FCC ARSCM7850 was DOA, Q811 was faulty and R8090 was burnt, I guessed at the value of R8090 to be approx 190 ohms, I replaced these components, after switch on the resistor starts to burn again, the whole area around these components and the KA3842 IC, was stained, almost like sea air corrosion, but only in a confined area. In an AOC-brand model with the same FCC number, R8090 was 22 ohms, 2 Watts. Besides checking Q811, other components that might be checked are Q812, Q823, C827, C828, C837, D806, D807, and check for any shorted windings in T804. The KA3842 IC may also have been damaged, and try to clean the stain off the PCB.

 

QUESTION NO. P60903-9:  EMC Multisystems SA-770 monitor FCC IJE765 has a shorted Q630 (IRF634A).  What other parts should I check or replace along with this mosfet so it doesn't short again? Check the flyback transformer and output transistor, one or both are faulty.Along with Q630, the ultrafast rectifier D632, and electrolytic C635, should also be replaced, as they are usually marginal or defective, as well (may not test totally bad). It has been suggested to reduce the value of C635, from 22 uF/250V, to 10 uF/250V.

 

QUESTION NO. P60603-5:  TVM AS6S monitor.  I need the value of R473. R473 is 20K ohms. When R473 burns, this is likely caused by a defective flyback transformer.

 

QUESTION NO. P60603-7:  Nec pn7701 monitor with open R304. Can't read the color code. R304 is 3.3 Ohms.

 

QUESTION NO. P60503-5:  Daytek DT-1501BA1 monitor FCC DTSCMC1501BA has horizontal line/squashed picture center of screen.  Resoldered five bad solder joints on vertical deflection circuit (TDA1675A) still have horizontal line.  Replace that IC.  It is a common failure in other monitors.  Also the cause is probably bad caps (4) connected to that IC. Then replace the b+ resistor (low value) connected to pin 14 which also has one of the caps on it.

 

QUESTION NO. P60203-3:  KDS VIEW K770 monitor, the horizontal output transistor (BU 2520-DF), C499 (220P 2kv) & R457 were burned.  I need the value of R457.This KDS model is a Jean chassis. R457 is 680 ohms, 1/2 Watt, and you probably meant disk capacitor C449, not C499. Also check Q426 and Q429 for potential damage.

 

QUESTION NO. P50503-1:  I need the vertical ic number for a Samsung Syncmaster 950p monitor. If this Samsung Syncmaster 950p is a PG19LS, then IC301 is TDA8172.   Samsung shows multiple chassis for this model. AQ19  IC301 as a KA2142, PG19  IC301 as a KA2142.

 

QUESTION NO. P52903-4:  AOC 7Glr monitor.  I need the value of R913 and R914. R913  4.7K 5% 1/4W, R914 47 ohm 5% 1/4W.

 

QUESTION NO. P52903-1:  HP D2818A monitor.  I need the number of Video IC IC 102 Missing (12Pin IC).  IC102 is LM2427.

 

QUESTION NO. P52703-3:  HP d2825 monitor cannot adjust horizontal size and has pincushion problem.  Replaced TDA4858, checked many components.  Other functions o.k.  Check Q302, Q303, R302, C316, L303, and D308. The semiconductors might be  leaky, but not totally shorted.

 

QUESTION NO. P51903-5:  LG studio works 775N monitor, is too dim.  I checked  power supply voltages they seem ok.  There is no burnt resistor or blown capacitor.  More than likely your CRT has low emission.  Had a lot of these fail at the end of the 3 year warranty.  LG ran out of replacement CRT's in Canada.

 

QUESTION NO. P52203-2:  Goldstar (LG) 1465DLs monitor FCC BEJCH480; Chassis: CA-32.  R726 burned (need value for replacement), also C723 (need value and specifications) seems burned too, both related to the FB. If both would be replaced, will they burn again?  R726 is 10K ohms, and C723 is 1 uF/63V. These were probably burned by a defective flyback, so the flyback would also need replacing, or they are liable to burn again.

 

QUESTION NO. P42803-2:  Acana Peripherals 17s monitor.  I need the value of burned R495 and the cause.If this Acana 17S is FCC# IIB-UA1, the schematic for that chassis shows R495 as 10K ohms. Since this R495 connects to the flyback transformer, a defective flyback might have burned R495.

 

QUESTION NO. P51603-1:  HP d2827a monitor, the hot has blown and I replaced it with a Bu2520df.  The ht is ok. When switched on the relay goes on and off with a tweaking sound. All voltages are correct with the hot disconnected. Is the bu2520df tre right transistor?  If this HP is a Daewoo 518X chassis, Daewoo's schematic shows BU2520DX, which is the same as BU2520AF electrically, except a different case style, so a BU2520AF should work in that chassis.

 

QUESTION NO. P51603-9:  Apple iMac 233 Mhz monitor.  When powered on, it goes through a procedure of bringing up the computer section of the iMac and then the monitor. When it gets as far as firing up the monitor board, there is a repeated snapping sound for between 1 and 5 seconds (I can see a small blue flash somewhere near the Motorola control chip), and then powers off and does not come back up unless left for an hour or so.  I can't see any burnt components on the board, but the top of the Motorola IC (LGM871-010/AYJ) appears to have heat damage (it's not a continuous black color on top like most ICs).  I have found only one supplier for the IC and it's $49 + shipping to the UK, so I don't want to replace it unless I know it is broken. The most common fault is shutdown due to an arcing flyback transformer, a common fault in the 233 MHz iMac. LG is one source for flyback 6174Z-1003G, or in some regions, an H.R. Diemen equivalent may be easier to obtain. 

 

QUESTION NO. P51503-7:  Sony cpdg500 monitor, brightness too high with all controls set at lowest possible.  Image is stable and in focus, all syncs and geometry ok.  Suspect defective ic in brightness circuit, possible voltage too high. No adjustments internally, all micro-controlled. Assuming that this is a circuitry fault, rather than a DAS software issue, the problem might be, that the CRT cathode voltages are too low, or the G2 voltage is too high. On the CRT board ('A' board), check if the cathode voltages (CRT pins 7,8,9) are in the 80 to 100 Volt range. If these voltages are too low, it may indicate a bad IC403 (FA4301). The

G2 voltage (CRT pin 10) should be roughly 522 Volts at the CRT. If G2 is much higher, check the G2 circuit, involving transistor pair Q406 & Q410, run by IC405 (pin 7), under control from IC404 (pin 14).  Otherwise, try a DAS alignment.

 

QUESTION NO. P41703-1:  Proline C409A monitor FCC IQX97C1455 is dead.  R122, R121, R130, Q101 and Q704 are all burned beyond recognition. I need the values. All other components are tested and seems OK. R121 is 220 ohms, R122 is 120 ohms, R130 is 10 Kohms, Q101 is 2SK2545, and Q704 is 2SC5339.  R121 and R122 form a voltage divider across R120, which is 0.47 ohms, and is the source return resistor for the MOSFET switch, Q101.  The junction of R121 and R122 goes to R110, 1000 ohms, which then feeds the current sense input of U101, which is a KA3882 PWM controller.  It seems unlikely that R121 and R122 could be burned unless R120 is open, and even then I would expect to see R110 burned unless there's a short on the board.

 

QUESTION NO. P51203-7:  Gateway EV700A monitor FCC BEJCB775B Voltage cycles. 5 Volts okay but all others cycle.  I replaced FBT and IC923, IC925. Also check IC304, the 8 Volt regulator IC on the CRT board, and its solder connections.

 

QUESTION NO. P50903-5:  Apple IMAC 266 Model M4984 monitor.  Is there an alternative flyback to 6174Z1017D (LG)?  Local LG list only 1017A or E. The A is not a cross but the E may be. Perhaps the E is an upgrade?  In iMac M4984, flyback# 6174Z1017D can be replaced by LG FBT# 6174Z-1003G.

 

QUESTION NO. P50803-5:  Proview pk-986 monitor FCC ije986.  I need the value for RT502.RT502 is an inrush-current limiter whose ohms rating is about 8 ohms at room temperature. A possible substitute might be a Thermometrics type CL110.

 

QUESTION NO. P50203-9:  Gateway2000 crystal Scan14 Mon014006A0WW monitor has very poor image, display is too dark.  Adjusting the screen causes the focus enhanced but still blurry.  I checked Q413= BU 2508DF it's ok. Check the CRT for poor emissions (dying CRT).

 

QUESTION NO. P50503-8:  Optiquest Q71 monitor powers off immediately.  I need the specs on burned voltage regulator Q429.  The board is version VCDTS21348-2M. Q429 is 2SC5248, rated 160 Volts, 1.5 Amp, 20 Watts, 150 MHz, DC gain 60-200, Cob 20pF, TO220F case. A 2SC3298 also might substitute for 2SC5248.

 

QUESTION NO. P50203-2:  Proview pk-986 monitor FCC ije986.  I need the value for R502 and Q502.  In the schematic for IJE986, Q502 is a 600 Volt, N-channel Mosfet, such as 2SK2141, 2SK2645, STP7NB60, or IRFBC40; (insulator added as required). R502 (47K) is shown in this schematic as being left open (not installed).

 

QUESTION NO. P42903-5:  Samton 45bn monitor.  In front panel buttons h size, pallelogram button and pinamp buttons are not working.  I replaced DM024 ic, still no change. Check if ultrafast diode D414 is leaky in reverse, or shorted. If D414 is not failing, then check Q412 and its associated components.

 

QUESTION NO. P42503-2:  LG Studioworks 795SC monitor Chassis CA-55, the power supply is bad! The TOPxxx and mosfet are burned.  Is there an replacement for this TOPxxx?  IC903 is TOP223Y; an LG/Goldstar supplier may be able to provide this IC, as LG part# 0IPF223000A.  L.J. Enterprises (www.ljecc.com) is also listing TOP223Y, on-line.

 

QUESTION NO. P33103-1:  I need to open the service menues of the Philips Brillianc 109p and a Nokia 446 pro monitors.    40 sites containing tv, vcr & computer monitor EEPROM service mode access: http://the-hideout.net/techtalk/phpbb2/viewtopic.php?t=47

 

QUESTION NO. P40103-9:  Compaq v410 model 304U monitor FCC BJMC4A Original problem: LED on the front would just flash amber never turned green. Replaced shorted HOT (C4916) with one that had the same specs with a slightly lower current rating. Now it powers up and displays a picture but I cannot get the horizontal adjustment far enough to the right and it starts to squish the picture the farther to the right I go. Also the new transistor runs extremely hot.  Original HOT 2SC4916 I replaced with 2SD1876 which according to the NTE cross are near identical except for the collector current. (10 amps versus 4 amps). I was expecting it to work but degrading the life of the transistor. I have now replaced it with the correct transistor and everything works fine. The NTE cross specs must be inferior or the max. collector current is more important then I imagined.

 

QUESTION NO. P32403-3:  Viewsonic G790 monitor has no red, green and blue normal. Trace the color signals to the CRT base PCB and swap two of the colors round (Hopefully the colors will be marked on the PCB).  If you now have RED, the tube is OK but the feed is faulty and vice-versa.

 

QUESTION NO. P42303-2:  I need the Sony manual part number for a Dell P992 monitor. The number on the P992 service manual is 9-978-704-01.

 

QUESTION NO. P42203-2:  LG 910sc monitor.  I need the value of burned FET Q901. The LG parts list shows Q901 as 2SK2843, which is a Toshiba 600 Volt, 10 Amp, 45 Watt Mosfet. 2SK2843 is listed as LG part no. 0TF284300AA. 

 

QUESTION NO. P41703-4:  Dell P1110 monitor (Sony chassis SCC-L22D-A), the CRT heater voltage is muted.  Applied external CRT filament supply, the picture appeared, but the screen is too high. Most times in the case of the missing heater voltage, there is usually a dried out electrolytic capacitor or bad inductor coil in the circuit. Check for one or the other. If the capacitor you find is suspected to be bad, you can parallel a known good one across it. If it is bad this should restore heater voltage somewhere around 7 volts DC.

 

QUESTION NO. P42203-6:  Optiquest Q71 monitor FCC GSSJ 17001 came from another shop. I replaced the shorted HOT.  It is working fine now but too wide.  Width control does not work.  Pincushion ok.  Check or replace D422, Q429, and Q411.

 

QUESTION NO. P42203-1:  Philips 15A12F monitor Chassis CM1200.  Need value of burnt R3426. R3426 is 4.7 ohms, 1/2 Watt.

 

QUESTION NO. P41703-7:  IBM 6558-03n monitor (Sony scc-l04h-a) shuts down deflection code.  Need part # or ic # for ic 702(vertical) which is missing.  The Sony schematic shows IC702 is LA7841L also check R720 1R 1/2W flame proof resistor and R727 1R 1/2W Flame proof resistor.

 

QUESTION NO. P31903-2:  Mag XJ717 Monitor.  The HOT shorted, but someone seems to have put in the the wrong type. I need the correct number of Q112.  Q112 is a BU2532AL.

 

QUESTION NO. P41503-10:  IIyama Visionmaster 400 monitor powers up without a signal connected and shortly goes into power save as expected but the power supply trips out when the PC / test card generator is connected. A

chirp is heard just before the power supply shuts down. If the monitor is powered with a signal connected, it shuts down instantly and won't power up again unless left for a few minutes.  I changed the FBT and the B+ smoothing caps to no avail. To answer my own question, I eventually found it necessary to change all the low value electrolytic capacitors (about 8 in total values between 1 and 100uf) in the primary side of the power supply. These capacitors checked okay but proved to be faulty by replacement.

 

QUESTION NO. P41503-4:  I need a Sony part no. ( 8-xxx-xxx-xx )  for a Sony IC (CXD9164M) from a Dell P992 monitor.  The Sony manual lists IC003 (CXD9164MTR) as Sony p/n# 6-700-723-01. (Not "8").

 

QUESTION NO. P41503-9:  LG Studioworks 440Si monitor.  I need the value of fried R843 near flyback. R843 is 12K ohms; check if a defective flyback had burned R843.

 

QUESTION NO. P41503-3:  Samsung Syncmaster 15GLi CMB5477L monitor was dead.  I replaced faulty Q503, 2SC5148 with a 2SC4747 and the faulty Q505, IRF740. I need the value of burnt R507 (in series with the Collector of Q503). R507 is 1.8ohm 2W. Also check C504 22uf 250V and C514 47uf 16V.

 

QUESTION NO. P41403-1:  Markvision VC1450D  model DA-456 AA monitor Chassis 2970005101.  I need the value of burned C441.  If its FCC is H79DA-456, a different brand, with this FCC, has a C441 of 220 pF, 2KV.

 

QUESTION NO. P41103-3:  Acana Advance 17S monitor FCC IIBUAI, I need value of R425. R425 is 10 ohms, 2 Watts, in the schematic for FCC# IIBUA1.

 

QUESTION NO. P41003-2:  Sony 200GS monitor has bad distortion at top of the screen. On cross hatch pattern, instead of vertical lines, it has vertical zigzag lines on top with an approximate length of 1.5cm in each line.  Try replacing C573. If C573 is no help, try other 250V capacitors, C572, C575, C524.

 

QUESTION NO. P41003-1:  DigiView AT398 monitor has a horizontal line across screen.  ICB02 is burned. Can only make out A8172. Believe this is the vertical amp. I do not see any other part that look overheated. 

This is a TDA8172 also check the diode between pins 2 & 6 and the capacitor between pins 3 & 6 and any resistors in the supply rail 2 and maybe 4 if it is supplied with + & - rails The full number is TDA8172.

 

QUESTION NO. P40803-7:  Viewsonic P810-1M / 21HV8SA monitor FCC GSS21001 - Need part numbers/subs and source for D602, D902, D905, R919, and Q902.  This is a repair for the common problem of leaking C852 causing shorted D602 and subsequent damage.  I am also replacing C852, C601, R602 as well.  Any other components affected outside of these? When you replace C852, also repair any damaged PCB traces under C852. D602 = MA167 (similar to 1N4148 or NTE519); D902 = MA4270NH (27V, 0.4W zener); D905 = MA4051NM (5.1V, 0.4W zener); R919 = 390 ohm SMD; Q902 = UN5211AI, an SMD digital transistor (SC-70 case style) with an internal 10K/10K resistor divider. If D905 has gone, I would be concerned about AC voltage continuing past, and possibly also damaging R917 (1.8K), R918 (100 ohm); IC850; and the processor IC901.

 

QUESTION NO. P40703-8:  Sony CPD200GS monitor has a normal picture on the bottom half of the screen, but is blank on the top half.  I have not located the vertical output IC. Does the vertical IC drive the yoke directly, or is there a transistor stage involved?  This looks like some kind of  push-pull output failure.IC401 drives the vertical yoke directly. This IC uses dual +/- 15 Volt supplies, so see if either supply is missing, or if either has a bad filter cap; C401, off pin 1; C404, off pin 6. If the supplies are both good, check IC401 itself, and associated components.

 

QUESTION NO. P40403-6:  Compaq Pe1120 monitor, the horizontal op and driver j449 was shot.  I need info on D310 (PH33D) which is broken in fragments.  This device is a Philips BYD33D rectifier, rated 200 Volts, 0.7/1.3 Amp (12A peak); Vf < 1.3V @ 1A.If; Trr < 250 nanoseconds; soft recovery.  Some possible substitutes include FR103, HER103, NTE552, and NTE574.

 

QUESTION NO. P31903-10:  Acer 7299c JVP7299c monitor, found shorted Horiz. output BU2532AN, replaced with 2SC3997 scoped output, pulse looked ok for 3 sec. blew output. Is this a suitable replacement? Drive circuit? No!  Fall time of 3997 is 0.2us and the 2532 is 0.06us. You may wish to check L304 & Q321 possibly burned & shorted. Check all coils and FBT these Acers are boomerangs.  They usually come back if you do not check everything.

 

QUESTION NO. P32103-8:  Hyundai DeluxScan 17B+ Model HL-7870A monitor is experiencing brightness problems, constant 'dimming' then 'brightening' of display. I replaced defective R502 and R503 but that did not work. Resolder G2 on Tube board and all the other tube connectors.

 

QUESTION NO. P32703-3:  Viewsonic 21PS monitor chassis HV4S/H  FCC GSS933006 is dead, LED comes on for 1 second then goes out. I replaced C839 and repaired arced trace under it and checked C867 it was OK. Repaired a few bad solder joints, one was cracked at Q583. It powers on now except HV.  Degauss works, tube heater works and menu controls will turn led green as will a PC when it is connected.  There is power to R588 and R589 but no power to R545. The degauss cable around CRT hits a capacitor on the front of the board and brakes the solder joint.

 

QUESTION NO. P33103-3:  Sony GDMF500 monitor with drifting focus and intermittent retrace, all main supply voltages checked ok, suspect focus divider.Before replacing the CP701 focus module, rule out if the CRT has an internal leak-path, which may occur in this model. Detach the CRT board from the CRT, and check with a high-voltage probe, to see if any voltage is leaking into the CRT's focus pins, etc, while under power. If any voltage is seen on the CRT pins while the CRT board is removed, there is an internal leak-path in the CRT.

 

QUESTION NO. P32403-1:  Viewsonic g810 monitor Chassis 21VS001(Panasonic), has no horiz sweep, hv is okay.  Thin vertical line from top to bottom. Check Q550, Q549, Q881, R890; there may also be a 0.8 Amp microfuse, marked "N11008", which resembles a small transistor, installed in the B+ path.

 

QUESTION NO. P32803-1:  Hyundai DeluxScan 5854 monitor.  I need a sub for Q303 (YTA 630) transistor. A substitute for YTA630 is IRF630.

 

QUESTION NO. P32703-6:  Packard Bell A720 monitor, FCC CKLA720.  Is there an alternate horizontal output transistor for 2SC5404? Possible substitutes for 2SC5404 might be 2SC5387 or 2SC5299.

 

QUESTION NO. P31303-3:  Dell D1025HT monitor has dim picture and no red color.  This was a comman fault of VPS12 IC.

 

QUESTION NO. P32603-2:  AcerView 7176ie monitor, the raster (without video input connected) flashed between black (normal) and high brightness.  With video input connected, there was video on the screen, but the brightness alternated between normal and high brightness.  Clicking sound could be heard as it flashed.  G1 on the video board varied from about +33V to -180V when it should be about -45V.  I replaced IC201 (TDA8351) and IC102 on the

video board, but did not solve the problem. Check/replace the three 450V electrolytics, C3950, C3951, C3952, their associated resistors (R3950, R3951, R3952), and the ceramic cap, C320 = 100pF/2KV.  It may be wise to also check the ESR on electrolytics C301, C304, C307, and C330.

 

QUESTION NO. P32403-7:  Dell  p991 monitor has no video.  Replaced Q901 (Irfi9634g) and Q902 (fs5km-18a, replaced with nte2958) both shorted.  I checked R934, C507, C644 and C914.  Since Q901 and Q902 are for driving flyback transformer T901, I would check if the FBT is bad. Also check gate-protection zeners D906 (10V) and D909 (15V), as well as B+ cap C913, and ultrafast D907. If the G2 voltage is low/missing, check R916, D910, and C919. An FS5KM-18A is rated at 900 Volts, a higher rating than NTE 2958 (700 Volts); is that NTE substitute FET still OK?

 

QUESTION NO. P31403-8:  Dell 1600h model D1626HS (Sony Chassis).  I need the value of missing Q640 in power supply.  R640 is open and looks like C641 has been replaced as there is carbon marks around it. Assuming this model is actually the Dell/Sony 1600HS/D1626HT, Q640 is the dual transistor, MX0841AB-F; you can get this from Sony, as their part# 8-729-041-12.  R640 = 0.1 ohm, 1/2 Watt, fusible; C641 = 470 pF/500V, ceramic.

 

QUESTION NO. P32003-8:  KDS VS195 EVOKD1900 monitor.  I need the part number or suitable cross for Q407 (mosfet).  Q407 is IRFS730. Mouser Electronics (www.mouser.com) lists IRFS730B, or else you can use IRF730 with an insulator. Also check or replace D409, D410, D411, D412; Q425; R497, R498; IC401; and the flyback transformer.

 

QUESTION NO. P31703-1:  TVM AS6S monitor.  I need the values of Q424, R495 and Q001.In my schematic, Q001 = IRF630, Q424 = 2SC3117, and R495 = 10K ohms.

 

QUESTION NO. P31003-3:  Compaq Presario MV520 monitor.  I need the value of burned R903 located between the + of the mains cap and Collector of Q902.  R903 is 33K Ohms.

 

QUESTION NO. P22603-4:  CTX VL950T FBT (Sampo FM1037D) monitor.  I need a sub or specs on the FBT within the UK. Sampo FBT = FM1037D = 47F13-07205, FBT is part# 47F13-0720s £26.44 inc VTA/P&P at Isotronic. 173 Martindale Rd, Hounslow, Middlesex, TW4 7EZ, 0208 577 6577 Tel, 0208 577 6657 Fax, 07939 273252

Mobile.

 

QUESTION NO. P31103-1:  Sony GDM200ps FCC AK8GDM200PS monitor is black screen when turned on, the power LED turns solid green for a few seconds and then goes off and immediately after that LED turns amber and blinks.  This happens irrespective of whether the vga cable is connected or not. It is on for 1.5 and off for 0.5 sec.That LED flash-time sequence implies a horizontal/vertical deflection failure, or thermal protection. The most common cause of deflection problems in this (N3) chassis, is a defective IC007 (CXA2043Q) chip, Sony part number 8-752-078-46.

 

QUESTION NO. P30603-8:  Gateway  EV700 Monitor  (LG - CA65 chassis) has very low brightness. It does control via the OSD menu.  All voltages are correct, including the CRT filament voltage and filaments are properly lit.  What should the G1 voltage be for proper brightness?  The G1 voltage in this unit is controlled from the OSD processor.  I have a voltage of neg 15v at maximum brightness and it goes further negative as I lower the brightness.   If I force the circuit more toward 0v or positive voltage, the unit seems to get a near normal brightness level. This unit has no G2 level control on the fbt, so there seems to be no other point at which the brightness level can be set.  I have checked this unit thoroughly for all possible bad caps and solder connections. This model the G2 is controlled by the Micon and is set by software and an interface.

 

QUESTION NO. P21703-6:  KTX GAG664SG monitor keeps blowing the line transistor after 2 hours.  I changed 2SC3886 and FBT. The drive is rough for some reason, a capacitor open the oscillator sparky etc. Check for a dry joint on a 470uF filter on the 12V line feeding the  oscillator.

 

QUESTION NO. P30503-5:  Acer 77c monitor has severe hourglass.  The components around IC202, TDA8351, the vertical IC, did not look burned or unusual.  I replaced IC202 anyway, but the problem was still there.  I measured many transistors in the horizontal area in circuit and they seemed to be good. Check C323 = 33 uF/250V.

 

QUESTION NO. P30503-6:  CTX 1760LR monitor. I need value for C333 (someone else removed from mb.)  C333 as 10 uF, 250 Volts.

 

QUESTION NO. P30503-7:  Dell Ultrascan P780, chassis SCC-L29K-A: monitor clicks on power up and then green light will turn amber and flash. HOT and all other components tested OK.  HV/+B  failure   Blink Amber on 0.5 sec off 0.5 sec.

H stop or V stop (included S-cap          Blink Amber on 0.5 sec off 0.5 sec. ABL Failure      Blink Amber on 0.5 sec off 1.5 sec. Aging/self-test  Blink Amber on 0.5 sec off 0.5 sec Blink Green on 0.5 sec off 0.5 sec.  I think the H stop or V stop is Amber on 1.5 sec: off 0.5 sec.

 

QUESTION NO. P22603-8:  KDS VSx-7 FCC EVOKD-1730 with R901 blown and power led only flickers, would like resistor value and any other recommendations.  R901 is 27K ohms. This resistor burns when the flyback is bad (and needs replacing). The bad flyback might also have damaged any of R902, R903, R904, Q411, and IC401.

 

QUESTION NO. P22103-3:  Hyndai hl-4848f monitor.  I need value for burned Q120 and Q121.  If this Hyundai is FCC# CKLHL-4850A, chassis C-1420, in that schematic, Q120 is shown as MPSA42, and Q121 is shown as C3198 (2SC3198).

 

QUESTION NO. P21803-5:  Hyundai Deluxscan 17B+ monitor (HL-7870A) has a faulty flyback transformer, no luck in sourcing this part, the transformer is not listed in the HR Diemen catalogue either.  I need an equivalent or source.  The original flyback is of DuGo brand and they do not reply to our emails.  The flyback transformer seems to cause every problem with these model monitors, the main problem is a dull screen caused by the flybacks inability to supply a sufficient voltage to the screen. overheating can also cause this. The flyback can also cause resistors to burn out!  You can also buy a blur buster which should solve the problem.

 

QUESTION NO. P21803-6:  LG cb563g monitor.  I need a sub for c5803 transistor on horizontal.  I tried bu508df and there is a white band coming on the left.  The KSC5803 is a 12 Amp HOT, and has no internal damper diode. BU508DF is only rated 8 Amps, and has a damper. To sub KSC5803, a 12 Amp HOT like 2SC4890, 2SC5048, or BU2525AF, would be more appropriate.  If it is actually KSC5803D ('D' suffix), then it does have an internal damper diode, and a HOT with an internal damper, like BU2525DF, might be used.

 

QUESTION NO. P21303-6:  Sony CPD-200ES monitor is dead, orange LED blinks.  Replaced blown C582 (102k 2kV) with no change. No HV to the CRT.  C582 is in the feedback circuit from Q507, back to IC904 = TDA9105. If it has blown, also check D903, D944, D945, D946, C944, R960, and IC904, along that circuit. 

 

QUESTION NO. P21303-10:  Princeton Ultra17+ monitor FCC EVOKD-1700V.  Q415, BC401 burned, need value.

Q415 can be BU2525AF or MJW16212.  BC401 is 0.68 Ohm, 1 Watt.

 

QUESTION NO. P21203-6:  Sony GDM200ps FCC AK8GDM200PS monitor is black screen when turned on, the power LED turns solid green for a few seconds and then goes off and immediately after that LED turns amber and blinks.  This happens irrespective of whether the vga cable is connected or not. This monitor has shut itself down for a suspected fault. Which circuit is at fault, is indicated by a code, given by the precise On and Off times (in seconds) of the Amber LED. If the LED is On for 0.5 sec, Off for 0.5 sec, this is a B+ failure. If On for 1.5 sec, Off for 0.5 sec, this is either a Horizontal or Vertical deflection failure, or thermal protection. If On for 0.5 sec, and Off for 1.5 sec, this is ABL failure. If On for 0.25 sec, Off for 0.5 sec, then On for 0.25 sec, and Off for 1.5 sec, this is High Voltage failure.

 

QUESTION NO. P21203-8:  Compaq Qvision200 Monitor model 480, FCC GZM1323.  I need the value of the resistor on the back side of the board (no number).  It is on the back side of T803.  I replaced C839, which was burned up, and then discovered this resistor on the back side was open.  The stripes are no longer legible due to the heat.  The value of that resistor is 330K Ohms, 1 Watt.  It may help to install a 2 or 3 Watt, instead.

 

QUESTION NO. P13003-8:  Acer 1555 monitor FCC JVP7254E displays horizontal line.  Replaced ic tda4866 but did not help.  Checked capacitor and resistor on vertical area and is all ok. Besides the resistors and electrolytics, also check if C220 has shorted.

Notes on the Diagnosis and Repair of Video Monitors V1.01Contents:

1) About the Author 2) Related Information 3) Safety 4) Most Common Problems 5) Monitor Manufacturing Quality and Cold Solder Joints 6) Intermittent or Missing Colors 7) Ghosts, shadows, or streaks in picture adjacent to vertical edges 8) Brightness Adjustment 9) Focus Problems 10) Arcing Spark-gaps 11) Dead Monitor with Periodic Tweet, Tweet, Tweet, or Flub, Flub, Flub 12) Smoking Monitor 13) Apple Monitor Dies after variable length of time 14) Magnetic Fields and Degaussing 15) Ultra Cheap Degaussing Coil 16) How Often to Degauss 17) Focus Adjustment 18) Interference from Electrical Wiring 19) Interference from other Equipment 20) Contour Lines on High Resolution Monitors 21) Monitor Reliability with SVGA 22) Lifespans of Monitors 23) Monitor Life, Energy Conservation, and Laziness 24) CRT Replacement - Probably not worth it 25) Monitor Drift? 26) Monitor Power Supplies 27) Single Vertical Line 28) Single Horizontal Line 29) Big Al's Rules of Thumb on Monitor Repair 30) Picture Gradually Darkens to Black 31) Training Manual (Skip) 32) Flyback Failure 33) Useful Service Aid

1) About the Author Here are the current version of my 'Notes on the Diagnosis and Repair of Video Monitors'

Author: Samuel M. GoldwasserE-Mail: sam@stdavids.picker.comCorrections/suggestions: [Feedback Form] [mailto]Copyright (c) 1994, 1995All Rights Reserved

Reproduction of this document in whole or in part is permitted if both of the following conditions are satisfied:

1. This notice is included in its entirety at the beginning. 2. There is no charge except to cover the costs of copying.

2) Related Information See the manuals on "Diagnosis and Repair of Small Switch Mode Power Supplies (SMPS)" (35KB) and "Failure Diagnosis and Repair of TVs" (50KB) for additional useful pointers. Since a monitor must perform a subset of the functions of a TV, many of the problems and solutions are similar. For power related problems the info on SMPSs may be useful as well.

You may also wish to see a typical SMPS found in a Panasonic VCR for a general "How they do it". You can find it at URL:http://www.paranoia.com/~filipg/HTML/FAQ/BODY/vcrps.ps (80KB).It's a Postscript file so deal with it accordingly. You may wish to read the Postscript FAQ **FIRST** if you have no clue on how to proceed. It's at URL:http://www.cis.ohio-state.edu/hypertext/faq/usenet/postscript-faq/top.html (SUBMENU).After you read the FAQ, and your questions are still unanswered, you may choose to ask your question on the group: comp.lang.postscript.

3) Safety General Safety Guidelines when working on line powered equipment including:

TVs Monitors Microwave Ovens

These guidelines are to protect you from potentially deadly electrical shock hazards as well as the equipment from accidental damage.

Note that the danger to you is not only in your body providing a conducting path, particularly through your heart. Any involuntary muscle contractions caused by a shock, while perhaps harmless in themselves, may cause collateral damage - there are many sharp edges inside this type of equipment as well as other electrically live parts you may contact accidentally.

The purpose of this set of guidelines is not to frighten you but rather to make you aware of the appropriate precautions. Repair of TVs, monitors, microwave ovens, and other consumer and industrial equipment can be both rewarding and economical. Just be sure that it is also safe!

Don't work alone - in the event of an emergency another person's presence may be essential. Always keep one hand in your pocket when anywhere around a powered line-connected or high

voltage system. Wear rubber bottom shoes or sneakers. Don't wear any jewelry or other articles that could accidentally contact circuitry and conduct

current, or get caught in moving parts. Set up your work area away from possible grounds that you may accidentally contact. Know your equipment: TVs and monitors may use parts of the metal chassis as ground return

yet the chassis may be electrically live with respect to the earth ground of the AC line. Microwave ovens use the chassis as ground return for the high voltage. In addition, do not assume that the chassis is a suitable ground for your test equipment!

If circuit boards need to be removed from their mountings, put insulating material between the boards and anything they may short to. Hold them in place with string or electrical tape. Prop them up with insulation sticks - plastic or wood.

If you need to probe, solder, or otherwise touch circuits with power off, discharge (across) large power supply filter capacitors with a 2 W or greater resistor of 100-500 ohms/V approximate value (e.g., for a 200 V capacitor, use a 20K-100K ohm resistor). Monitor while discharging and/or verify that there is no residual charge with a suitable voltmeter. In a TV or monitor, if you are removing the high voltage connection to the CRT (to replace the flyback transformer for example) first discharge the CRT contact (under the insulating cup at the end of the fat red wire). Use a 1M-10M ohm 1W or greater wattage resistor on the end of an insulating stick or the probe of a high voltage meter. Discharge to the metal frame which is connected to the outside of the CRT.

For TVs and monitors in particular, there is the additional danger of CRT implosion - take care not to bang the CRT envelope with your tools. An implosion will scatter shards of glass at high velocity in every direction. There are several tons of force attempting to crush the typical CRT. Always wear eye protection.

Connect/disconnect any test leads with the equipment unpowered and unplugged. Use clip leads or solder temporary wires to reach cramped locations or difficult to access locations.

If you must probe live, put electrical tape over all but the last 1/16" of the test probes to avoid the possibility of an accidental short which could cause damage to various components. Clip the reference end of the meter or scope to the appropriate ground return so that you need to only probe with one hand.

Perform as many tests as possible with power off and the equipment unplugged. For example, the semiconductors in the power supply section of a TV or monitor can be tested for short circuits with an ohmmeter.

Use an isolation transformer if there is any chance of contacting line connected circuits. A Variac(tm) is not an isolation transformer! The use of GFCI (Ground Fault Circuit Interrupter)

protected outlet is a good idea but will not protect you from shock from many points in a line connected TV or monitor, or the high voltage side of a microwave oven, for example. A circuit breaker is too slow and insensitive to provide any protection for you or in many cases, your equipment.

Don't attempt repair work when you are tired. Not only will you be more careless, but your primary diagnostic tool - deductive reasoning - will not be operating at full capacity.

Finally, never assume anything without checking it out for yourself! Don't take shortcuts!

4) Most Common Problems

Intermittent changes in color, brightness, size, or position. Ghosts, shadows, or streaks in picture adjacent to vertical edges. Magnetization of CRT causing color blotches or other color or distortion problems. Monitor not syncing on one or more video scan ranges. Adjustments needed for background brightness (SCREEN) or focus. Dead monitor due to power supply problems.

5) Monitor Manufacturing Quality and Cold Solder Joints Any intermittent problems with monitors that cause random sudden changes in the picture brightness, color, size, or position are often a result of bad connections.

Bad solder joints are very common in monitors due both to poor quality manufacturing as well as to deterioration of the solder bond after numerous thermal cycles and components running at high temperature. Without knowing anything about the circuitry, it is usually possible to cure these problems by locating all bad solder connections and cleaning and re-seating internal connectors. The term 'cold solder joint' strictly refers to a solder connection that was either not heated enough during manufacturing, was cooled too quickly, or where part pins were moved before the solder had a chance to solidify. A similar situation can develop over time with thermal cycling where parts are not properly fastened and are essentially being held in by the solder alone. Both situations are most common with the pins of large components like transformers, power transistors and power resistors, and large connectors. The pins of the components have a large thermal mass and may not get hot enough during manufacturing. Also, they are relatively massive and may flex the connection due to vibration or thermal expansion and contraction.

These problems are particularly common with TVs and monitors - especially cheaper monitors.

To locate cold solder joints, use a strong light and magnifier and examine the pins of large components for hairline cracks in the solder around the pin. Gently wiggle the component if

possible (with the power off). Any detectable movement at the joint indicates a problem. With the power on, gently prod the circuit board and suspect components with an insulated tool to see if the problem can be effected.

When in doubt, resolder any suspicious connections. Some monitors may use double sided circuit boards which do not have plated through holes. In these cases, solder both top and bottom to be sure that the connections are solid. Use a large enough soldering iron to assure that your solder connection is solid. Put a bit of new solder with flux on every connection you touch up even if there was plenty of solder there before. However, remove any obvious excess. Inspect for solder bridges, sliver, splashes, etc. before applying power.

6) Intermittent or Missing Colors This is a catchall for some of the most common monitor problems. Most of the causes boil down to bad connections of one form or another.

1. VGA or other video input cable. Sometimes these develop intermittent problems at the connector to the VGA board. These may be internal to the cable in which case it will need to be replaced or if you are handy and have infinite patience, you can replace just the VGA connector.

Alternatively, the male pins of the cable may not be making good contact with the female VGA socket. First try contact cleaner. If this does not work, gently squishing the male pins with a pair of needle-nose pliers may provide temporary or permanent relief if the pins are a tad too small. However, if you go too far, you can damage or break the pins or cause the female sockets to become enlarged and loose fitting for any other monitor you may use.

There may be cold solder joints on the VGA board itself at the VGA connector. These can be resoldered.

2. Printed circuit board on the CRT neck. This is a common location for cold solder joints. Check with a bright light and magnifying glass for hairline cracks around the pins of larger parts. Prod and tap with an insulated tool to see if the problem is effected. Resolder if necessary.

3. Cold solder joints elsewhere in monitor usually around the pins of large parts such as transformers, power transistors and resistors, and internal connectors. Inspect with a strong light and magnifier if necessary.

4. Internal connectors that need to be cleaned and reseated. Remove, clean with contact cleaner, burnish, and replace.

7) Ghosts, shadows, or streaks in picture adjacent to vertical edges Complaints about these kinds of problems are very common especially as the screen resolution and necessary video bandwidth keeps increasing. Most are due to cable and video termination deficiencies and not actual monitor defects.

The video signals for red, green, and blue (or just a single signal for monochrome) are sent over cables which are generally 75 ohm transmission lines. These are coaxial cables that may be combined inside a single sheath for VGA, SVGA, MACs, and many workstations but may be separate coaxes with BNC (or other) connectors for other video applications.

Without going into transmission line theory, suffice it to say that to obtain good quality video, the following conditions must be met:

1. A good quality of cable must be used. This means one in which the characteristic impedance is close to the optimum 75 ohms, one which has low losses, and one which has good shielding. For installations using BNC connectors, a good quality of 100% shielded RG59U is often used. The BNC connectors must be properly installed or they will contribute to mismatch problems.

2. Where multiple monitors are to be connected to a single video source, all wiring is done in a daisy chain fashion. The only taps permitted are the minimum necessary to connect each monitor to the chain. This usually means a BNC-T connector or a pair of connectors on the monitor for each video signal. T connections with cable must be avoided.

3. Only the last monitor in the chain should be terminated in 75 ohms. All of the others must be set to Hi-Z. Monitors with BNC connectors will usually have one switch or a switch for each color to select termination.

Monitors for PCs, MACs, and workstations usually have built in termination and do not offer the choice of Hi-Z. This means that without a video distribution amplifier, it is not possible to connect multiple monitors of this type to a single video source with any expectation of a good quality display.

Failure to follow these rules will result in video ringing, ghosts, shadows, and other unsightly blemishes in the picture. It is often not possible to control all aspects of the video setup. The cable is often a part of the monitor and cannot easily be substituted for a better one. The monitor may not have properly designed circuitry such that it degrades the video regardless of the cable and display board quality. The display card itself may not have proper drivers or source termination.

Ironically, the better the video card, the more likely that there will be visible problems due to termination. This is due to the very high bandwidth and associated signal edge rates.

Some examples of common termination problems:

Overly bright picture with trails following vertical edges, perhaps with periodic ringing. This is due to a missing termination. Check if the monitor is set for Hi-Z instead of 75 ohms. If there is no switch, then the termination may be faulty or the monitor may need an external resistor. For BNC connectors, plug-on terminations are available.

Bright ghost images adjacent to vertical lines. This may indicate that the terminating resistor is greater than the impedance of the cable. You may be using Ethernet Thinnet cable by accident which is RG58 with an impedance of 50 ohms.

Dark picture and ghost images adjacent to vertical lines. This may indicate that the terminating resistor is too low - multiple monitors on a chain all set for 75 ohms instead of just the last one. Or, an improper type of cable such as audio patch cord.

Fuzzy vertical edges. This may indicate a poor quality cable or a run which is just too long. For high resolutions such as 1280x1024, the maximum cable length may be as short as 25 feet or less for poor quality cable. Better cable or fiber-optic repeaters may be necessary.

Other similar problems - check cables for defective or improperly installed connectors. This is especially applicable to cables with BNC or UHF type connectors which require a kind of artistic talent to assembly properly and consistently.

If only 1 or 2 colors (of the R, G, and B) are effected, then look for improper switch settings or bad connections (bad cable connectors are really common) on the problem color cables.

8) Brightness Adjustment A monitor which has a picture that is very dark and cannot be adequately set with the user brightness and contrast controls may need internal adjustment of the screen (the term, screen, here refers to a particular electrode inside the CRT, not really the brightness of the screen you see, though it applies here), master brightness, or background level controls. As components age, including the CRT, the brightness will change, usually decrease. The following procedure will not rejuvenate an old CRT but may get just enough brightness back to provide useful functionality for a few months or longer. If the problem is not with the age of the CRT, then it may return the monitor to full brightness. The assumption here is that there is a picture but the dark areas are totally black and the light areas are not bright enough even with the user brightness control turned all the way up.

In most cases, the cover will need to be removed. The controls we are looking for may be located in various places. Rarely, there will be access holes on the back or side.

The controls may be located on the:

Flyback transformer. Usually there is a master screen control along with a focus control on the flyback transformer.

A little board on the neck of the CRT. There may be a master screen control. a master brightness control, a master background level control, or individual controls for red, green, and blue background level. Other variations are possible. There may also be individual gain/contrast controls.

Main video board is less common, but the background level controls may be located here.

Display a picture at the video resolution you consider most important which includes both totally black and full white areas which also includes sharp vertical edges.

Set the user brightness control to its midpoint and the user contrast control as low as it will go - counterclockwise.

Let the monitor warm up for at least 15 minutes so that components can stabilize.

If there is a master brightness or background level control, use this to make the black areas of the picture just barely disappear. Them, increase it until the raster lines just appear. (They should be a neutral gray. If there is a color tint, then the individual color background controls will need to be adjusted to obtain a neutral gray.) If there is no such control, use the master screen control on the flyback. If it is unmarked, then try both of the controls on the flyback - one will be the screen control and the other will be focus - the effects will be obvious. If you did touch focus, set it for best overall focus and then get back to the section on focus once you are done here.

If there are individual controls for each color, you may use these but be careful as you will be effecting the color balance. Adjust so that the raster lines in a black area are just visible and dark neutral gray.

Now for the gain controls. On the little board on the neck of the CRT or on the video or main board there will be controls for R, G, and B gain or contrast (they are the same). If there are only two then the third color is fixed and if the color balance in the highlights of the picture was ok, then there is nothing more you can do here.

Set the user contrast control as high as it will go - clockwise.

Now adjust each internal gain/contrast control as high as you can without the that particular color 'blooming' at very bright vertical edges. Blooming means that the focus deteriorates for that color and you get a big blotch of color trailing off to the right of the edge. You may need to go back and forth among the 3 controls since the color that blooms first will limit the amount that you can increase the contrast settings. Set them so that you get the brightest neutral whites possible without any single color blooming.

Now check out the range of the user controls and adjust the appropriate internal controls where necessary. You may need to touch up the background levels or other settings. Check at the other resolutions and refresh rates that you normally use.

If none of this provides acceptable brightness, then either your CRT is in its twilight years or there is something actually broken in the monitor. If the decrease in brightness has been a gradual process over the course of years, then it is most likely the CRT. As a last resort (untested) you can try increasing the filament current to the CRT the way CRT boosters that used to be sold for TVs worked. Voltage for the CRT filament is usually obtained from a couple of turns on the flyback transformer. Adding an extra turn will increase the voltage and thus the current making the filament run hotter. This will also shorten the CRT life - perhaps rather

drastically. However, if the monitor was headed for the dumpster anyhow, you have nothing to lose.

9) Focus Problems Slight deterioration in focus can be corrected by adjusting the focus control usually located on the flyback transformer. Sometimes, this is accessible externally but usually not. On monochrome monitors, the focus control, if any, may be located on the main board.

Don't expect to have perfect focus everywhere on the screen. Usually there will be some degradation in the corners. A compromise can generally be struck between perfect focus in the center and acceptable focus in the corners.

If the adjustments have no effect, then there is probably a fault in the focus power supply.

For most color TVs and monitors, the correct focus voltage will be in the 4-8 KDC range so you will need a meter that can go that high or some big resistors to extend its range or a HV probe. You must use a high impedance meter as the current availability from the focus power supply is very low.

The pots in the flyback are sometimes accessible by removing their cover, which may snap on. However, a typical focus circuit will have a large value resistor potted inside the flyback (like 200 Megohms).

Try to measure the focus in-circuit. If the value you read is very low (assuming your meter has a high enough impedance not to load the circuit appreciably), then disconnect the wire (from the PCB on the neck of the CRT or wherever) and measure again and observe any change in picture.

If still low, then almost certainly there is a problem with the pot or the flyback. See if you can open it enough to measure and/or disconnect the pot. If the problem is inside the potted part of the flyback, the only alternative is a new flyback or an external divider if you are so inclined. However, once the focus network goes bad inside the flyback, there is an increased chance other parts will fail at some point in the future.

If the voltages check out with the CRT disconnected, there is a chance of a bad CRT or of a shorted component on the PCB on the neck of the CRT. Look for shorted capacitors or burnt or damaged traces.

10) Arcing Spark-gaps If after removing the cover on a monitor that has power but has no picture or a very dim distorted picture, you find visible arcing at one of the spark-gaps near the CRT, then most likely there is a short inside of the flyback transformer or HV multiplier (if used). In either case, replacement will be needed for the offending component. These spark-gaps are designed to protect the CRT electrodes from excessive voltages. Do not be tempted to remove the spark-gap - it is serving its protective function.

11) Dead Monitor with Periodic Tweet, Tweet, Tweet, or Flub, Flub, Flub A monitor which appears to be dead except for a once a second or so tweet or flub usually indicates a fault in the switching power supply - often a shorted rectifier. The HFR854s (one common type in monitors) or other high speed high efficiency rectifiers in the output side of the switching power supply seem to like to turn into short circuits. (I had a couple of DOA monitors where this was the problem. so much for quality control!) This could also be due to other shorted component such as the horizontal output transistor where there is a separate switching power supply.

After unplugging the monitor and waiting a few minutes for the filter capacitors to discharge (check with a voltmeter but stay away from the CRT HV connector as it may retain a dangerous and painful charge for a long time), use an ohmmeter across the various diodes in the power supply. These appear commonly as black cylinders about 3/8" long by 1/4 diameter. (Kind of like 1N400Xs on steroids). The resistance of the diodes in at least one direction should be greater than 100 ohms. If it is much less (like 0 or 5 ohms), then the diode is probably bad. Unsolder and check again - it should test infinite (greater than 1M ohms) in one direction. If it now tests good, there may be something else that is shorted.

Replacements are available for about $.25 from places like MCM Electronics.

Check other power semiconductors as well, in particular, the horizontal output transistor.

Other possible causes: bad solder connections, other shorted components like capacitors, other problems in the power supply. Sometimes this is an indication of an over-voltage shutdown due to a faulty regulator or open load.

12) Smoking Monitor Smoking is just as bad for monitors as for people and usually more quickly terminal.

White acrid smoke may indicate a failed electrolytic capacitor in the power supply probably in conjunction with a shorted rectifier. Needless to say, pull the plug at once.

A visual inspection should be able to easily confirm the bad capacitor as it will probably be bulging and have condensed residue nearby. Check the rectifier diodes or bridge rectifier with an ohmmeter. Resistance across any pair of leads should be more than a few ohms in at least one direction. Remove from the circuit to confirm. Both the faulty diode(s) and capacitor should be replaced (though the capacitor may work well enough to test with new diode(s).

If a visual inspection fails to identify the smoking part, you can probably plug the monitor in for a few seconds until the source of the smoke is obvious but be prepared to pull the plug in a real hurry.

13) Apple Monitor Dies after variable length of time This is a (Apple) Sony 13" monitor, 4 years old. After being turned on for 30 minutes, the display goes completely blank and the front LED goes off. If the power is shut off for 10 minutes or so, it will come back on for another 15 minutes or so, then go blank again, etc. The +120v and +65v from the power module is still present when it blanks out, but no other voltages (+12, +960, etc) are present on the main circuit board. I've been told it might be the HV capacitor is bad; would like to hear a 2nd or 3rd opinion before buying a new capacitor.

That is the same diagnosis a friend of mine got for her monitor with that identical problem. Replacing the capacitor did fix the problem.

That 'capacitor' is a big red thing is a Sony part which includes some kind of low voltage connection as well. The guy at the place where she got it repaired said that the capacitor is one of the most common problems with those monitors. $70 for the part + $50 for labor, ouch! Only, apparently available from Sony. Why can't Sony design monitors like everyone else? Sure, I know, theirs are better (well, except for the unsightly stabilizing wires on Trinitrons!).

14) Magnetic Fields and Degaussing Indications of need for degaussing are small or large areas of the screen where the colors are not correct or where color balance has suddenly changed. There are other possible causes - both electronic and mechanical - but stray magnetic fields is numero uno on the list.

The shadow mask or aperture grill of the CRT - the fine mesh just behind the phosphor screen - is normally made of a material (steel or InVar) which is easily magnetized. This can happen just by rotating the monitor on its swivel, by moving it from one place to another, by switching on or off some piece of electronic equipment near the monitor, even by a local lightning strike.

Since any stray magnetism effects the color purity and convergence, it is important that the CRT is demagnetized before use.

15) Ultra Cheap Degaussing Coil Pack Rat Trick #457384

Next time you scrap a computer monitor (or a color tv), save the degaussing coil (coil of wire, usually wrapped in black tap or plastic) mounted around the front of the tube. To adapt it for degaussing sets, wrap it into a smaller coil, maybe 4"-6". To limit the current to something reasonable, put it in series with a light bulb (60-100W). You need AC current to degauss, so just put the bulb in series with the coil and use the your local 120V outlet. BE VERY CAREFUL that you actually wired it in series, and that everything is properly insulated before you plug it in (A fuse would be a real good idea too!!)

A few circles over the affected area will usually do it. Note that it will also make your screen go crazy for a little bit, but this will fade out within a minute or so.

Disclaimer: This has worked consistently for me in the past, but I make absolutely no warranty as to the safety or effectiveness of this procedure in your situation. But if you try it and like it, feel free to let me know!

Just a couple of points for emphasis:

1. The coil as removed from the TV is not designed for continuous operation across the line as indicated above. In fact, it will go up in a mass of smoke without the lightbulb to limit the current. The poor TV from which this organ was salvaged included additional circuitry to ramp the current to 0 in a few seconds after power is turned on.

2. Reducing the coil size by a factor of 2 or 3 will increase the intensity of the magnetic field which is important since we are limiting the current with the lightbulb to a value lower than the TV used. You don't need to unwind all the magnet wire, just bend the entire assembly into a smaller coil. Just make sure that the current is always flowing in the same direction (clockwise or counterclockwise) around the coil.

3. Insulate everything very thoroughly with electrical tape. A pushbutton momentary switch rated for 2 amps at 115 volts AC would be useful so that you do not need to depend on the wall plug to turn it on and off.

16) How Often to Degauss Some monitor manufacturers specifically warn about excessive use of degauss, most likely as a result of over stressing components in the degauss circuitry which are designed (cheaply) for only infrequent use. In particular, there is often a thermistor that dissipates significant power for the second or two that the degauss is active. Also, the large coil around the CRT is not rated for continuous operation and may overheat.

If one or two activations of the degauss button do not clear up the color problems, manual degaussing using an external coil may be needed or the monitor may need internal purity/color adjustments. Or, you may have just installed your megawatt stereo speakers next to the monitor!

You should only need to degauss if you see color purity problems on your CRT. Otherwise it is unnecessary. The reasons it only works the first time is that the degauss timing is controlled by a thermsistor which heats up and cuts off the current. If you push the button twice in a row, that thermister is still hot and so little happens.

One word of clarification: In order for the degauss operation to be effective, the AC current in the coil must approach zero before the circuit cuts out. The circuit to accomplish this often involves a thermister to gradually decrease the current (over a matter of several seconds), and in better monitors, a relay to totally cut off the current after a certain delay. If the current was turned off suddenly, you would likely be left with a more magnetized CRT. There are time delay elements involved which prevent multiple degauss operations in succession. Whether this is by design or accident, it does prevent the degauss coil - which is usually grossly undersized for continuous operation - to cool.

17) Focus Adjustment One of the most common complaints is that the monitor is not as crisp as it used to be - or just not as sharp as expected.

Assuming that the focus has just been gradually getting worse over time, tweaking the internal focus control may be all that is needed.

On most monitors, the flyback transformer includes two control - FOCUS and SCREEN. The one you want is, of course, FOCUS.

Safety: As long as you do not go near anything else inside the monitor while it is on AND keep one hand in you pocket, you should be able to do this without a shocking experience.

Plug it in, turn it on and let it warm up for a half hour or so. Set your PC to display in the resolution you use most often. First turn the user brightness and contrast fully counterclockwise. Turn brightness up until the raster lines in a totally black area appear, then back a hair until they disappear. Then, turn the contrast control up until you get a fairly bright picture. Fully clockwise is probably ok. Adjust FOCUS for generally best focus. You will not be able to get it razor sharp all over the screen - start at the center and then try to get the edges and corners as good as you can without messing up the center too much. Double check that the focus is OK at your normal settings of brightness and contrast.

The SCREEN control adjusts background brightness. If the two controls are not marked, you will not do any damage by turning the wrong one - it will be immediately obvious as the brightness

will change rather than focus and you can then return it to its original position (or refer to the section on brightness adjustments to optimize its setting).

18) Interference from Electrical Wiring If the wiring of normal outlets is done correctly even without a safety ground, the currents should be balanced and you will not experience a problem. However, many circuits, particularly those involving setups like 3-way switches or switched outlets and wiring in older buildings can have unbalanced currents when active. If your monitors are close enough to the wiring, there can be interference which will take the form of a flickering or pulsating display.

Other than recommending moving the monitors, there is no easy solution. They can be shielded with Mu Metal but that is expensive. Or you could run all displays at a 60 Hz vertical rate (or 50 Hz depending on where you live). However, this is inconvenient and will never be quite perfect.

19) Interference from other Equipment Any type of equipment which uses or generates strong magnetic fields can interfere with a monitor. Other computer monitors or TVs, equipment with power transformers, and electric motors will cause a pulsating or flickering display. Loudspeakers or other equipment with static magnetic fields will cause color purity and/or geometric distortion problems which degauss will not cure.

The easiest way to confirm that interference is your problem is to move the monitor or suspect equipment to a different location. The only real solution is to separate the monitor and interfering device.

20) Contour Lines on High Resolution Monitors These fall into the category of wavey lines, contour lines, or light and dark bands even in areas of constant brightness. These may be almost as fine as the dot pitch on the CRT or 1 or 2 cm or larger and changing across the screen. If they are more or less fixed on the screen and stable, then they are not likely to be outside interference. (However, if they are locked to the image, then there could be a problem with the video board.)

One cause of these lines is Moire (interference patterns) between the raster and the dot structure of the CRT. Ironically, the better the focus on the tube, the worse this is likely to be. Trinitrons, which do not have a vertical dot structure should be immune to interference of this sort from the raster lines (but not from the horizontal pixel structure).

You can test for Moire by slowly adjusting the vertical size. If it is Moire, you should see the pattern change in location and spatial frequency as slight changes are made to size. Changes to vertical position will move the patterns without altering their structure - but they will not remain locked to the moving image.

The patterns will remain essentially fixed in position on the face of the CRT for horizontal size and position adjustments - the patterns will remain fixed under the changing image.

How to eliminate it? If Moire is your problem, then there may be no easy answer. For a given resolution and size, it will either be a problem or not. You can try changing size and resolution - Moire is a function of geometry. Ironically, I have a monitor which is nicer in this respect at 1024x768 interlaced than at 800x600 non-interlaced.

Another cause of similar problems is bad video cable termination creating reflections and ghosting which under certain conditions can be so severe as to mimic Moire effects. This is unlikely to occur in all colors with a VGA display since the termination is internal to the monitor.

21) Monitor Reliability with SVGA There are parts in the monitor which may get hotter with SVGA but if it is designed for SVGA resolution, there should be no problem (assuming you are not running in an excessively hot room or with the ventilation holes covered).

A good quality multisync monitor should not mind switching screen resolutions frequently (though doing it every few seconds continuously may stretch this a bit).

Newer multisync monitors should also be smart enough not to blow up if you feed then a scan rate which exceeds their capabilities. However, there are a lot of poorly designed monitors out there.

If it is supposed to run SVGA, use it at SVGA. If it blows up, switch to a different brand. There are a lot of crappy monitors being sold on their own and bundled with PCs.

22) Lifespans of Monitors Most manufacturers will quote an MTBF (Mean Time Before Failure) of somewhere in the 30,000 to 60,000 hour range, EXCLUSIVE OF the CRT. The typical CRT, without an extended-life cathode, is usually good for 10,000 to 15,000 hours before it reaches half of its initial brightness. Note that, if you leave your monitor on all the time, a year is just about 8,000 hours.

The only "tuneup" that a monitor should need, exclusive of adjustments needed following replacement of a failed component, would be video amplifier and/or CRT biasing adjustments to compensate for the aging of the tube. These are usually done only if you're using the thing in an application where exact color/brightness matching is important. Regular degaussing of the unit may be needed, of course, but I'm not considering that a "tuneup" or adjustment. (Bob Myers | myers@fc.hp.com)

23) Monitor Life, Energy Conservation, and Laziness A common misconception about the care and feeding of computer monitors is that they should be left on all the time. While there are some advantages to this, there are many more disadvantages:

CRT Life

The life of a monitor is determined by the life of the CRT. The CRT is by far the most expensive single part and it is usually not worth repairing a monitor in which the CRT requires replacement. The brightness half-life of a CRT is usually about 10-15 K hours of on time independent of what is being displayed on the screen. 10 K hours is only a little more than a year. By not turning the monitor off at night, you are reducing the life of the monitor by a factor of 2-3. Screen savers do not make any substantial difference especially with modern displays using X-Windows or MS Windows where the screen layout is not fixed. With video display terminals, the text always came up in the same position and eventually burned impressions into the screen phosphor.

Component life

The heat generated inside a monitor tends to dry out parts like electrolytic capacitors thus shortening their life. These effects are particularly severe at night during the summer when the air conditioning may be off but it is still a consideration year around.

Safety

While electronic equipment designed and manufactured in accordance with the National Electrical Codes is very safe, there is always a small risk of catastrophic failure resulting in a fire. With no one around, even with sprinklers and smoke alarms, such an failure could be much more disastrous.

Energy use

While modern monitors use a lot less energy than their older cousins, the aggregate energy usage is not something to be ignored. A typical monitor uses between 60 and 200 Watts. Thus at a $.10 per KWH electric rate such a monitor will cost between $48 and $160 a year for electricity. During the night, 1/2 to 2/3 of this is wasted for every monitor that is left on. If air

conditioning is on during the night, then there is the additional energy usage needed to remove this heat as well - probably about half the cost of the electricity to run the monitor.

The popular rationalization for what is most often just laziness is that power-on is a stressful time for any electronic device and reducing the number of power cycles will prolong the life of the monitor. With a properly designed monitor, this is rarely an issue. Can you recall the last time a monitor blew up when it was turned on? The other argument, which has more basis in reality is that the thermal cycling resulting from turning a monitor on and off will shorten its life. It is true that such thermal stress can contribute to various kinds of failures due to bad solder connections. However, these can be easily repaired and do not effect the monitor's heart - the CRT. You wouldn't leave your TV on 24 hours a day, would you?

Some of the newest ('green') monitors have energy conserving capabilities. However, it is necessary for the software to trigger these power reduction or power down modes. Few monitors in actual use and fewer workstations or PCs are set up to support these features. If you have such a monitor and computer to support it, by all means set up the necessary power off/power down timers. However, using the power saving modes of a 'green' PC with an older monitor can potentially cause damage since some of the modes disable the sync signals. A 'green' monitor which can detect a blank screen and and use this as a trigger can easily be used with a screen saver which can be set to display a blank screen - on any PC or workstation.

Please make it a habit to turn your monitors off at night. This will extend the life of the monitor (and your investment) and is good for the environment as well. For workstations, there are good reasons to leave the system unit on all the time. However, the monitor should be turned off using its power switch. For PCs, my recommendation is that the entire unit be turned off at night since the boot process is very quick and PCs are generally not required to be accessible over a network 24 hours a day.

24) CRT Replacement - Probably not worth it The sad fact is that even if you can obtain a new CRT you won't have the proper setup for getting proper alignment and convergence. They generally use various permanent magnet glued to the perimeter of the yoke to set the geometry of the raster. It takes a special factory jig to do this step or really great persistence and patience. I have done it for monochrome monitors without too much difficulty.

25) Monitor Drift? Problem: I have a 17" monitor that has an image that EVER SO SLIGHTLY drifts to the left (and stops) after a long day's work (heat, I suppose). Also, the vertical height shrinks a little bit. Is this at all normal/acceptable?

How much is 'ever so slightly'? There are a fair number of components whose values could alter the position/size of a monitor image. I do not find it at all surprising that there should be a small shift due to heat. It really depends on many factors including the basic design, quality of components, ventilation/cooling, etc. Of course, it is possible to have a monitor that has a component that is worse with respect to temperature. Could also be related to line voltage depending on the regulation of your monitor's power supplies.

In general, my feeling is that if it is not objectionable (a 1/2" shift would be objectionable) AND it's severity is not changing with time, you can ignore it.

Many monitors do this. TVs do this but you are not aware of it since they are already 5-10% overscanned for just this reason, as well as compensating for component aging and line voltage fluctuations.

26) Monitor Power Supplies Monitors use a variety of switching supply techniques and it would be difficult to cover every possibility but here are some comments:

Probably the most common is deflection derived - the voltages are obtained from auxiliary windings on the horizontal flyback (HV) transformer. A number of components can be at fault and produce a 'dead' monitor. The switching supply could also be independent of the HV supply, but this is less common, especially on inexpensive monitors.

Some possibilities:

Horizontal output transistor (usually a TO3 metal or TOP3 plastic case shorts out. This will usually blow a fuse or fusible resistor as well.

Horizontal drive chain - horizontal oscillator, driver, or driver transformer. Newer monitors may use an IC for the oscillator and this can fail.

Startup - There may be some kind of startup circuit which gets the whole thing going until the auxiliary voltages are available. This could be as simple as a multivibrator or transistor regulator to provide initial voltage to the horizontal oscillator chip or circuit.

Output rectifier diodes can fail shorted and load down the outputs to the point of shutting down.

Some load could be shorted or a capacitor could be shorted leading to overload and shutdown.

Flyback transformer can have shorted windings which load down the output. These (primary shorts in particular) may cause the horizontal output transistor to fail as well. Common problem with older MacIntosh computers and video terminals.

Also, look for cold solder joints - monitors tend to have these as a result of temperature cycling and bad manufacturing. (Is this sounding repetitive yet?)

Sometimes there is a series regulator after the filter cap and this could be bad as well.

I guess I would attempt to trace the circuit from the main filter cap assuming that has the proper (approx. 150-160 VDC usually) voltage.

If there is no voltage at the main capacitor, then there is probably a blown fuse or bad connection somewhere. However, the fuse may have blown due to a fault in the switcher.

If you can locate the horizontal output transistor, see if there is voltage on its collector, should be the same. If there is, then there is probably a drive problem. If you have an ECG or similar semi cross reference, that will help you identify the ICs and transistors and locate the relevant portions of the circuitry.

27) Single Vertical Line Since you have high voltage, the horizontal deflection circuits are almost certainly working (unless there is a separate high voltage power supply - almost unheard of in modern TVs and very uncommon in all but the most expensive monitors).

Check for bad solder connections between the main board and the deflection yoke. Could also be a bad horizontal coil in the yoke, linearity coil, etc. There is not that much to go bad based on your symptoms assuming the high voltage and the horizontal deflection use the same flyback. It is almost certainly not an IC or transistor that is bad.

28) Single Horizontal Line A single horizontal line means that you have lost vertical deflection. High voltage is most likely fine since there is something on the screen.

This could be due to:

1. Dirty service switch contacts. There is often a small switch on the located inside on the main board or perhaps accessible from the back. This is used during setup to set the color background levels. When flipped to the 'service' position, it kills vertical deflection and video to the CRT. If the switch somehow changed position or got dirty or corroded contacts, you will have this symptom. Flip the switch back and forth a couple of times. If there is some change, then replace, clean, resolder, or even bypass it as appropriate.

2. Bad connection to deflection yoke or other parts in vertical output circuit. Bad connections are common in TVs and monitors. Check around the pins of large components like transformers, power transistors and resistors, or connectors for hairline cracks in the solder. Reseat internal connectors. Check particularly around the connector to the deflection yoke on the CRT.

3. Bad vertical deflection IC or transistor. You will probably need the service manual for this and the following. However, if the vertical deflection is done with an IC, the ECG Semiconductor Master Substitution guide may have its pinout which may be enough to test it with a scope.

4. Other bad parts in vertical deflection circuit though there are not that many parts that would kill the deflection entirely.

5. Loss of power to vertical deflection circuits. Check for blown fusable resistors/fuses and bad connections.

6. Loss of vertical oscillator or vertical drive signals.

The most likely possibilities are in the deflection output stage or bad connections to the yoke.

29) Big Al's Rules of Thumb on Monitor Repair

1. Use an isolation transformer. A variac can be helpful too. A cheap isolation transformer can be constructed by wiring two identical transformers of adequate power capability back-to-back. (Here is a use for those old boat anchors you can't bear to part with).

2. If it's just the power supply or flyback switching transistors that have failed, then the repair is probably easy enough and quick enough to be worthwhile. Blown power transistors are trivial to locate in the circuit and quite easy to find replacements for. In many cases I've found that the monitor would have lived a much longer life if only the transistor mounting screws had been tightened properly by the manufacturer. Make sure you use appropriate replacements and the proper heat sink parts and heat sink compound.

3. If it's the flyback transformer, then judgment should be made based on the cost and availability of the replacement part. Also, on the risk of there being additional problems beyond that of the bad flyback. Who gets to eat the cost of the part in the event you don't succeed and give up? However, determining that the flyback is indeed at fault may prove challenging without a flyback tester. Sometimes there will be obvious damage such as burnt marks, cracked plastic, or other signs of overheating. If you have the correct resistance measurements, then for the primary you may be able to detect shorted windings. You can also construct the brute force flyback tester at the end of the document.

4. If it's the CRT then make the project "someone else's problem" and give the monitor to someone else to use as a parts carcass. My life is much happier since I learned there is no disgrace in making this choice.

5. There is another common failure category which is a result of people who are too lazy to turn off the power switch at night. The constant heat causes the electrolytic capacitors to dry out and become intermittent. I often replace all of the smallest electrolytic in the power supply section especially when I know the switching transistor is good. If after a couple of hours of labor and a dozen caps I still don't have it running, I give up on these too.

6. Be realistic with yourself about the value of a used working monitor. CGA's EGA's and monochrome Hercules monitors rarely fetch more than $25 at a swap meet.

7. Don't sell a used monitor to a friend unless you want to continue repairing the thing until you're old and grey.

8. Don't put a scope on the collector of the supply or flyback transistors, unless you have a special X100 high voltage / high frequency scope probe.

30) Picture Gradually Darkens to Black Symptom: Intermittently, the picture darkens smoothly to black over a period of 10-15 seconds. A tap on the side of the monitor sometimes restores the picture (this time it "lightens" to normal over 10-15 seconds). The picture is otherwise essentially unchanged in size, position, color, and focus.

This sounds like the filament to the CRT is losing power. Since the picture is otherwise unchanged, look really carefully for cold solder joints particularly on the little board on the back of the CRT if there is one and/or on any connectors associated with the CRT socket. There isn't much to the filament power supply - it is usually a couple of turns of wire on the flyback. If all colors are more or less equally effected, the it is not the CRT itself as the 3 filaments are welded in parallel to the socket pins.

31) Training Manual (Skip) I recently attended a monitor repair course put on by Philips electronics. They have a technical training manual titled:

"HI-RES Computer Display Systems"part # ST1496-1093LE/KGPGC

I am sure this can be ordered from Philips Service Co. P.O. Box 555, Jefferson City, TN 37760 phone 615-475-0044

This book does an excellent job of explaining how these monitors work. Most is about Philips monitors but the material is applicable to most manufacturers. This course and reading this text has help me a lot with my monitor repair efforts.

Skip, e-mail skipperm@mtc2.mid.tec.sc.us

32) Flyback Failure Flybacks fail in several ways:

1. Overheating leading to cracks in the plastic and external arcing. These can often be fixed by cleaning and coating with multiple layers of high voltage sealer, corona dope, or even plastic electrical tape (as a temporary repair in a pinch).

2. Cracked or otherwise damaged core will effect the flyback characteristics to the point where it may not work correctly or even blow the horizontal output transistor.

3. Internal shorts in the FOCUS/SCREEN divider network, if present. One sign of this may be arc-over of the FOCUS or SCREEN spark-gaps on the PCB on the neck of the CRT.

4. Internal short circuits in the windings. 5. Open windings.

For the low voltage windings, service manuals may provide the expected DC resistance (SAM's PhotoFact, for example). Sometimes, this will change enough to be detected - if you have an ohmmeter with a low enough scale. These are usually a fraction of an ohm. Open windings, of course can be located with an ohmmeter and service notes. It is difficult or impossible to measure the DC resistance of the HV winding since the rectifiers are usually built in. The value is not published either.

(4) (and sometimes (3) as well) will drastically lower the Q and increase the load the flyback puts on its driving source with no outputs connected. A Q meter or transformer tester can be used, but since many people do not have such equipment, here is a circuit that should work. The only caution is that this tester probably does not put enough stress on the flyback to find an intermittent that fails only under operating conditions.

It is just a 12 V chopper feeding the salvaged core from a flyback. The secondary of this core is a 10 turn coil. You will need to remove the suspect flyback from the TV or monitor. A second 10 turn coil is wound on the suspect flyback anywhere it will fit. Connect one end of each coil securely. Provide an easy way of connecting the other ends momentarily - a push button comes in handy.

If the flyback is good, then with the coils connected there will be several KV at its output - enough to create a small arc (1/8" typical). The load imposed on the oscillator will be modest (the frequency increases in response to load). If there are any shorted windings, then there will be no significant HV output and the load on the oscillator will increase dramatically.

The circuit is shown below. None of the component values are critical.

+12 Q1 +-----------------C || o | C || | B |/ C C || <-- Flyback Under Test ---> | +------| 2N3055 C || | | |\ E 5T C || C-------|>|----------o +HV | | | C || C HV Diode, usually | | -_- C || C built in | | C || _____ C

+--|--------------------------C ||C C||C | | Q2 _-_ C ||C 10T C||C | | | C ||C ea. C||C | | B |/ E 5T C ||C C||C | | ----| 2N3055 C ||C__/ _C||C | | | |\ C C || C | | | | C || C | | | +-----------------C || C | | | || C | | ------------------------C || C-------------------o -HV | | 2T C || | | +----------C || (Numerous other windings not shown) | | | 2T C || | +--------------------------C || | | | R1 | R2 +----------/\/\/\--+--/\/\/\---+ 110 27 _|_ 2W 5W -

33) Useful Service Aid When testing TVs and monitors after repairing power supply problems, it is desirable to put a limiting resistance like a lightbulb in series with the power line to prevent your newly installed expensive components from destroying themselves should there still be a problem. When using a homemade degaussing coil, you may also may need a limiting resistor.

An easy and flexible solution for both these needs is to construct an electrical box with a duplex outlet where the individual outlets have been separated and wired in series - line-1->hot 1, neutral-1->hot-2, neutral-2->line 2. Clearly mark on the box as to how it is wired.

Now, you can plug your monitor into one outlet and a suitable lamp into the other. For a TV or monitor, use a 100-150 W bulb. For testing a VCR power supply, use a 24-40 W bulb. You could use a lamp with a 2-way switch as well. For your degaussing coil, as large a load as your wire can stand can be plugged into the other outlet. This is safer and easier than using alligator clip leads.