TM 11-6665-245-34

TECHNICAL MANUAL

DIRECT SUPPORT ANDGENERAL SUPPORT MAINTENANCE MANUAL

RADIAC SET AN/PDR-56F(NSN 6665-01-113-9530)

This copy is a reprint which includes current

pages from Change 1.

HEADQUARTERS, DEPARTMENT OF THE ARMY

14 JANUARY 1983

SAFETY STEPS TO FOLLOW IF SOMEONEIS THE VICTIM OF ELECTRICAL SHOCK

DO NOT TRY TO PULL OR GRAB THE INDIVIDUAL

IF POSSIBLE TURN OFF THE ELECTRICAL POWER

IF YOU CANNOT TURN OFF THE ELECTRICALPOWER, PULL, PUSH, OR LIFT THE PERSON TOSAFETY USING A WOODEN POLE OR A ROPE ORSOME OTHER INSULATING MATERIAL

SEND FOR HELP AS SOON AS POSSIBLE

AFTER THE INJURED PERSON IS FREE OFCONTACT WITH THE SOURCE OF ELECTRICALSHOCK, MOVE THE PERSON A SHORT DISTANCEAWAY AND IMMEDIATELY START ARTIFICIALRESUSCITATION

CHANGE

NO. 1

TM 11-6665-245-34C1

HEADQUARTERSDEPARTMENT OF THE ARMY

WASHINGTON, DC, 15 January 1986

DIRECT SUPPORT AND GENERAL SUPPORTMAINTENANCE MANUALRADIAC SET AN/PDR-56F

(NSN 6665-01-113-9530)

TM 11-6665-245-34, 14 January 1983, is changed as follows:

1. Remove and insert pages as indicated below.

2. New or changed material is indicated by a vertical bar in the margin of the page.

3. Added or revised illustrations are indicated by as vertical bar adjacent to the figure caption.

Remove Pagesi and ii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1/( 1-2 blank) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1 thru 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1 and 3-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-5 and 3-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-9 thru 3-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-1/(A-2blank) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .None . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Insert Pagesi and ii1-1/( 1-2 blank)2-1 thru 2-4none3-1 and 3-23-5 and 3-63-9 thru 3-14A-1/(A-2 blank)FO-2

4. File this change sheet in front of the publication.

By Order of the Secretary of the Army:

Official:

JOHN A. WICKHAM JR.General, United States Army

Chief of Staff

MILDRED E. HEDBERGBrigadier General, United States Army

The Adjutant General

DISTRIBUTION:To be distributed in accordance with DA Form 12-36 literature

requirements for AN/PDR-56F.

TM 11-6665-245-34

W A R N I N G S

The check source used in this equipment contains Thorium (a radioactivemetal). Thorium is a hazardous material. Injury or disease may result if theThorium check source is not handled properly. Observe the following precau-tions:

Do not scratch or abrade the check source in any way to produce small par-ticles. If small particles are produced, use extreme caution to avoid inhalation.

Do not allow particles to enter the body, through open cut or mouth. Washany area suspected of being contaminated with Thorium with luckwarm waterand a non-abrasive soap. Contact qualified medical personnel and the localRadiological Protection Officer (RPO) immediately if you are exposed to checksource material. Use extreme care not to touch, scratch, or break or remove thesurface of the check source while handling them.

Never place a dislodged check source in your pocket. Do not clean checksource with abrasives. Refer to TB 43–01 16, TB 43–0122, and AR 385-11 forinstructions on first aid, safe handling, storage and disposal of radioactivematerial.

High voltages produced in this equipment are exposed when the radiacmetercase is removed and the equipment turned on. Be careful when performingmaintenance, take the following precautions:

Never work on the radiacmeter when you don’t know the hazards. Becomefamiliar with components that contain or hold high voltage and where highvoltage is exposed to contact before turning the equipment on.

Work on the equipment without the equipment on whenever possible.Protect yourself to reduce injury due to accidental contact with high

voltage. Use one hand to make measurement and keep the other hand (or body.parts) off ground to eliminate current path through your body.

Become familiar with methods of Artificial Respiration, refer to FM 21-11.

a/(b blank)

TM 11-6665-245-34

Technical Manual HEADQUARTERSDEPARTMENT OF THE ARMY

No. 11-6665-245-34 WASHINGTON, DC, 14 January 1983

DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE MANUALRADIAC SET AN/PDR-56F

(NSN 6665-01-113-9530)

REPORTING ERRORS AND RECOMMENDING IMPROVEMENTS

You can help improve this manual. If you find any mistakes or if you know of a wayto improve the procedures, please let us know. Mail your letter, DA Form 2028(Recommended Changes to Publications and Blank Forms) or DA Form 2028-2located in back of this manual direct to Commander, US Army Communications-Electronics Command and Fort Monmouth, ATTN: AMSEL-ME-MP, Fort Monmouth,NJ 07703-5007.

In either case, a reply will be furnished direct to you.

TABLE OF CONTENTS

Paragraph

CHAPTER 1. INTRODUCTIONSection I. General

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1Consolidated Index of Army Publications and Blank Forms . . . . . . . . . . . . 1-2Maintenance Forms, Records and Reports . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3Reporting Equipment Improvement Recommendations (EIR). . . . . . . . . . . 1-4

Section Il. Description and DataDescription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5Tabulated Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

CHAPTER 2. FUNCTIONING OF EQUIPMENTIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1Block Diagram Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2Probe Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3Probe Electronics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4Discriminator, Buffer-lnverter Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5Count Rate Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6Power Supply and Regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

CHAPTER 3. MAINTENANCESection I. General

Maintenance Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Maintenance Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Equipment Required for Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operational Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Il. Repair of RadiacmeterRemoval and Replacement of Cover Assembly . . . . . . . . . . . . . . . . . . . . . .Removal and Replacement of PCB Assembly . . . . . . . . . . . . . . . . . . . . . . . .Removal and Replacement of Meter Light Assembly and Meter... . . . . . .Repair and Replacement of Source Assembly . . . . . . . . . . . . . . . . . . . . . . .

3-13-23-33-43-5

Section3-63-73-83-9

Page

1-11-11-11-1

1-11-1

2-12-12-12-2.12-2.12-42-4

3-13-13-53-53-5

3-63-63-73-7

Change 1 i

TM 11-6665-245-34

TABLE OF CONTENTS l Continued

CHAPTERSection

Section

APPENDIX

Figure

2-12-22-32-42-52-62-73-13-23-33-43-53-63-73-8

FO-1FO-2

3.Ill.

IV.

A.

MAINTENANCE - ContinuedRepair of ProbesRepair of Main Probe and Emitter FollowerRepair of the Aux Probe . . . . . . . . . . .Repair of the X-Ray Probe . . . . . . . . .Testing Repaired Equipment

Paragraph

. . . . . . . . . . . . . . . . . . . . . . . . . . 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12

Source Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13Light-Leak Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14Calibration of the Radiacmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15Calibration of the X-Ray Probe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16

REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

LIST OF ILLUSTRATIONS

Title

Particle Detector Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .X-Ray Probe Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Main Probe Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Probe Circuit Simplified Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Discriminator Buffer-lnverter Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Count Rate Circuit Simplified Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Regulated Power Supply Simplified Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . .AN/PDR-56F Wiring Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PCB Parts Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Voltage Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Radiacmeter, Exploded View.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Main Probe, Exploded View.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Aux Probe, Exploded View... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .X-Ray Probe, Exploded View. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .X-Ray Probe,DT-590A/PDR-56, PCB Parts Locations . . . . . . . . . . . . . . . . . . . . . . . . . . .AN/PDR-56F Schematic Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Overall Schematic, X-Ray Probe, DT-590A/PDR-56F . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

3-73-103-10

3-113-113-113-12

A-1

Page

2-22-2.22-32-32-52-52-63-23-33-43-83-93-93-133-14

Fold outillustrationlocated inback ofmanual

LIST OF TABLES

Table Title Page

3-1 General Support Troubleshooting Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-53-2 Operational Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

ii Change 1

TM 11-6665-245-34

CHAPTER 1INTRODUCTION

Section I.

1-1. ScopeThis manual covers direct and general supportmaintenance for Radiac Set (AN/PDR-56F). It in-cludes instructions for direct and general supportto troubleshoot and test the equipment and toreplace maintenance parts. Detailed functions ofthe component parts of the radiac set are also in-cluded.

1-2. Consolidated Index of Army Pub-lications and Blank Forms

Refer to the latest issue of DA Pam 310-1 to deter-mine whether there are new editions, changes oradditional publications pertaining to the equip-ment.

1-3. Maintenance Forms, Records andReports

a. Reports of Maintenance and Unsatisfac-tory Equipment. Department of the Army formsand procedures used for equipment maintenancewill be those prescribed by ‘DA Pam 38-750tained in Maintenance Management Update.

Section II

1-5. Description

as con-

GENERAL

b. Report of Packaging and Handling Defi-ciencies. Fill out and forward SF 364 (Report ofDiscrepancy (ROD)) as presribed in AR735-11-2/DLAR 4140.55/NAVMATINST 4355.73A/AFR400-54/MC0 4430.3F.

c. Discrepancy in Shipment Report. Fill outand forward Discrepancy in Shipment Report(DISREP) (SF361) as prescribed in AR55-38/NAVSUPINST 4610.33C/AFR 75-181MC0P4610.19D/DLAR 4500.15.

1-4. Reporting Equipment ImprovementRecommendations (EIR)

If your Radiac Set AN/PDR-56F needs improve-ment, let us know. Send us an EIR. You, the user,are the only one who can tell us what you don’tlike about your equipment. Let us know why youdon’t like the design. Tell us why a procedure ishard to perform. Put it on an SF 368 (Quality Defi-ciency Report). Mail it to Commander, US ArmyCommunications-Electronics Command and FortMonmouth, ATTN: AMSEL-ME-MP, Fort Mon-mouth, NJ 07703-5007. We’ll send you a reply.

DESCRIPTION AND DATA

1-6. Tabulated DataRefer to TM 11-6665-245-12, Operator’s and Organ- Refer to TM 11-6665-245-12, Operator’s and Organ-izational Maintenance Manual for Radiac Set izational Maintenance Manual for Radiac SetAN/PDR-56F, for a general description and il- AN/PDR-56F, for applicable tabulated data.lustrations of the equipment.

Change 1 1-1/(1-2 blank)

TM 11-6665-245-34

CHAPTER 2FUNCTIONING OF EQUIPMENT

2-1. IntroductionThe radiac set is composed of a Radiacmeter lM-160F/PDR-56 (radiacmeter), three probes: DT-224B/PDR-56 (main probe), DT-228A/PDR-56 (aux-iliary probe), and DT-590A/PDR-56F (X-ray probe), aset of earphones, an extension handle, a carryingstrap, an operator’s technical manual, and a caseto contain the components. The radiac set is usedto detect and measure alpha radiation whichpenetrates the detecting screen of the main probe(or auxiliary probe) and to detect and measure lowenergy gamma radiation with the x-ray probe con-nected to the radiacmeter. The functioning of theequipment will be explained first on a blockdiagram and then on a detailed analysis of the cir-cuitry.

2-2. Block Diagram Analysis(Fig. 2-1)

The operating portion of the radiac set includesthe radiacmeter and the main, auxiliary, and x-rayprobes. These items and their circuitry are laid outon the block diagram (fig. 2-1) with the direction ofsignal flow from left to right. The signal starts inthe probe (main, auxiliary, or x-ray) and ends up asboth a meter indication and a sound indication inthe headset.

a. Reg Power. This block supplies power andvarious voltages to operate the radiacmeter. Thepower is taken from two dry cells that are in-stalled in the radiacmeter. The relatively lowvoltage of the dry cells is stepped up through anosci l lator- t ransformer-rect i f ier arrangementwhich suppl ies the di f ferent vol tages. Theregulator portion of this block is used to maintainoutput voltage constant as the dry cell voltagechanges slightly over the battery life.

b. Probes. The main and auxiliary probes con-vert low energy alpha particles into pulses of lightfor the photomultiplier tube. The x-ray probesenses low energy gamma radiation and pro-duces voltages of sufficient amplitude, which arepassed by the discriminator and fed to the countrate meter, which shapes and displays the eventsper unit of time in the meter circuit.

c. Photomult ip l ier and Emit ter Fol lower.These items are contained in the handle of themain (and auxiliary) probes. The photomultiplierchanges the light pulses from these probes intoelectrical signals. The emitter follower providesimpedance matching to the coiled cable which

connects the main and auxiliary probes to theradiacmeter body.

d. Discriminator. This block represents twotransistors connected to discriminate betweenlow level random noise and actual signals. Thediscriminator allows signals to pass to the nextblock, but eliminates the noise signal. The outputsignal from this block is a constant amplitudepulse which coincides with the light pulse to thephotomultiplier (PM) for the beta probes. With thex-ray probe, which has an amplifier-discriminatorcircuit integral to the probe (self-contained with ascintil lator-photomultiplier combination), theresul t ing s ignal i s c o u p l e d t o t h e m a i ndiscriminator as shown in the block diagram atFigure 2-2.

e. Buffer-Inverter. In this block, the signal isinverted and sent to the count rate circuit.

f. Count Rate. The count rate block provides achangeable timing circuit so that scales can bechanged. Part of the circuit is the scale changeswitch which selects the proper timing com-ponents for changing scale.

g. Indicating Meter. This block represents themeter on which the counts per minute (CPM) areread.

h. Headset Connector. Provides an outputconnection for listening to the signal (clicks).

2-3. Probe OperationBoth the main probe and the auxiliary probeoperate on the same general principle. They bothconvert alpha particles to pulses of light and thenconvert those light pulses to an electrical signal(electrical pulses). The. x-ray probe converts gam-ma rad ia t ion inc iden t to i t s sc in t i l l a to r -photomultiplier from light pulses to an electricalsignal.

a. Main Probe. Figure 2-3 shows a cut awayview of the inside of the main probe. The base andcover fo rm a l i gh t t i gh t cover ing fo r thephotomultiplier tube. Slots cut into the metalbase bottom form the area (window) where alphaparticles are detected. The window area is alsosealed to keep light from entering by a sandwichformed of a piece of clear Iucite and a piece ofvery thin aluminum foil bonded to clear plastic(aluminized mylar). Directly above the aluminizedmylar is a layer of phosphor, a chemicalsubstance that gives off light when activated byradiation. Above the Iucite are pieces of clear

Change 1 2-1

Figure 2-1.

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1

1-6

66

5-2

45

-34

2-2 Change 1

plastic called light pipes which direct lightgenerated in the phosphor to the photomultipliertube. Alpha particles are detected when the baseof the probe is placed over or close to materialsg iv ing o f f a lpha rays . The a lpha par t i c lepenetrates the phosphor through the slots in thebase and the aluminized mylar. Each alpha parti-cle activates the phosphor it penetrates causing asmall speck of light to be generated. The light inturn is directed through the light pipes to thephotomultiplier where the light is changed to anelectrical signal.

b. Auxiliary Probe. The auxiliary probe func-tions in the same manner as the main probe ex-cept that it is smaller and has no light pipes.

c. X-Ray Probe.

NOTEIn addition to emitting 5.1 MeV alphaparticles, the element Plutonium-239also emits x-rays in the energy range of14 to 21 keV. Because these x-rays aremore penetrating than the alpha par-ticles, they travel further in matter andair and can be detected at furtherdistances from the ground.

The x-ray probe uses a CaF 2 (Eu) scintillator-photomultiplier combination to detect the 14-21keV x-rays from Pu-239. The photomultiplier tubefits into a tube socket with a voltage divider net-work to supply the dynode voltages. A mu-metalshield surrounds the phototube to protect it fromgain changes due to stray magnetic fields or fromchanges in orientation with respect to the earth’smagnetic field. The x-ray probe is an assemblywhich includes the amplifier-discriminator cir-cuits integral to the phototube scintillator hous-ing. The discriminator is a single channel analyzeradjusted to detect Pu-239 x-rays.

TM 11-6665-245-34

trons are released from it than strike it and theyare attracted to dynode two because it is morepositive than dynode one. This action continuesthrough nine dynodes providing more and moreelectrons as it gets closer to the collector (pin 10).The collector absorbs the electrons and they flowto ground through resistor R11 forming a negativegoing voltage pulse which represents the alphaparticle which has been detected.

(2) Transistor Q1, resistors R12 and R13and capacitors C3 and C4 are used to counteractthe effect of the coil cord capacitance on thesignal. The output of the transistor Q1 is a low im-pedance to match the coil cord. Resistor R12 andcapacitor C4 form an integrating circuit to shapethe pulse waveform. Capacitor C3 and resistorR13 counteract the distributed capacitance of thecoil cord to ground.

b. X-Ray Probe. (Figure FO-2). The X-Ray Pro-be circuitry contains a PM tube (V2), a pulseamplifier (Q10, 11, 12) and a simple channelanalyzer (U1,2). Voltages of -950 VDC, + 3.38 VDC,and -9 VDC are supplied from the radiacmeterthrough the coiled cord. The signal from the x-rayprobe is also carried to the radiacmeter throughthe coil cord.

. (1) With t h e l o w e r and upperdiscriminator (U1) thresholds at typical -2.3 VDCand -6 VDC respectively, the amplifier gain is ad-justed such that the low discriminator triggers forenergies 14 keV and above and the upperdiscriminator triggers for energies 22 keV andabove. U2 (pins 1, 2, 3, 4, 6) is a one shot whichshapes the output pulses. U2 (pins 10, 11, 12, 14) isa flip-flop which is set by the upper discriminatoroutput and thus inhibits the one shot output.

(2) Resistors R64, R65, and R66 areshorted as needed to provide the required voltagefor the photomultiplier tube (V2).

2-5. Discriminator, Buffer-lnverter Circuit 2-4. Probe Electronics

(Figures 2-4 and FO-2)a. Main and Auxiliary Probes. The probe cir-

cuitry contains a photomultiplier tube (Vi) andtransistor Q1. Voltages of minus 950 and minus 9are supplied from the radiacmeter through thecoil cord. The signal from the main probe (and)auxiliary probe is also carried to the radiacmeterthrough the coil cord.

(1) V1, the photomultiplier tube, receiveslight pulses on its cathode. A light pulse releaseselectrons from the cathode which are attracted todynode one (pin 1) because it is more positivethan the cathode. When the electrons from thephoto cathode strike the first dynode, more elec-

(Figure 2-5)The discriminator and buffer-inverter circuit deter-mines the level of pulses which are measured andprovides a positive going pulse for use by thecount rate circuit (U1).

a. In the static condition, Q2 is conductingand Q3 and Q4 are held cut off. The positivevoltage from voltage divider consisting of R17 andR18 biases Q2 on and sets the emitter voltage ofQ2 positive. This in turn biases Q3 off whichbiases Q4 off.

b. Negative going pulses are received fromthe probe along with noise across resistor R14.Before the negative going pulse can cut off Q2, itmust overcome the positive bias set by R18. R18

Change 2 2-2.1

Figure 2-2.

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11-6665-245-34

2-2

.2

Ch

an

ge

2

TM 11-6665-245-34

Figure 2-3. Main Probe Section

Figure 2-4. Probe Circuit Simplified Schematic Diagram

Change 1 2-3

TM 11-6665-245-34

is set so that small magnitude signals (noise) areeliminated.

c. Once Q2 is cut off, Q3 and Q4 turn on pro-viding a positive going pulse to be formed acrossresistor R21.

2-6. Count Rate Circuit(Figure 2-6)

a, The count rate circuit consists of NOR gateU1A, NOR gates U1B through U1D connected assimple inverters, and transistor Q5 which is usedin a feedback loop to control U1A. Prior to anysignal (positive pulse from the buffer inverter cir-cuit Q4), the inputs (pins 1 and 2) to NOR gate U1Aare both low, the output (pin 3) is high and tran-sistor Q5 is conducting.

b. The positive going pulse from the buffer-inverter starts the circuit into operation. When pin2, U1A, goes high, pin 3, its output goes low. Thevoltage change is coupled directly to the base ofQ5 through timing capacitor C21. Q5 is then cutoff and its collector goes high holding the outputof U1A low. This condition holds until timingcapacitor C21 discharges through resistor R23enough to allow Q5 to turn on, causing pin 1 ofU1A to revert to a low condition. This actionresults in pin 3, U1A, first going low as the resultof the inverter-buffer input pulse and then stayinglow until the timing capacitor discharges forminga negative going pulse on the input of U1Bthrough U1D.

c. The negative going pulse at pin 3, U1A, isstarted by the inverter-buffer pulse. Its length isdetermined by the discharge time of C21 when S1is in the position shown. When S1 is in otherranges, the value of the timing capacitor changesand so does the length of the output pulse. Thesedifferent pulse lengths are used for differentranges and cause the meter to read correctly asscales are changed.

d. Outputs from U1B and U1C are tiedtogether and connected to the indicating meterthrough potentiometer R26, resistor R27, switchS1, and resistor R33. Since the meter cannot res-pond to the pulse, capacitor C23 is connected

across the meter. The capacitor is charged by thepulse and then discharges through R33 and themeter to provide a steady reading on the meter.Capacitor C24 is switched into the meter circuiton the 1M and 1K positions of the selector switch and combines with C23 to change the time cons-tant required on those ranges.

e. The output of U1D is used to energize theheadphones (when used) and provides the “click”noise in the earpiece for each pulse received from the inverter-buffer stage.

2-7 . Power Supply and Regulator (Figure 2-7)

The power supply and regulator circuit uses thevoltage input from the two radiacmeter batteries.T h e o u t p u t v o l t a g e s w h i c h o p e r a t e t h eradiacmeter circuits are: minus 950, minus 9, andplus 3.8 volts dc. These voltages are generatedfrom a blocking type oscillator circuit using stepup voltage windings to generate an ac voltagewhich is rectified for the dc voltages.

a. The blocking oscillator circuit uses tran-sistor Q6 as the oscillator. The feedback for theosc i l l a to r i s p rov ided by w ind ing 4 -5 o ftransformer T1 coupled through the transformer’score. The feedback signal alternately cuts off Q6and drives it into saturation. The length of time Q6is cut off is controlled by the charge on capacitorC17 and C18. The charge path for C17 and C18 isthrough and controlled by transistor Q7. Tran- sister Q7, in turn, is controlled by the differentialamplifier pair of transistors Q8 and Q9 to set thecharge (voltage of C18). Controlling the voltage onC18 then controls the time Q6 is cut off, whichcontrols the frequency of the oscillator and thethree power supply outputs.

b. Three ac output voltages are taken fromtransformer T1. There is a separate winding bet-ween pin 6 asnd either pins 7 through 11 for thehigh voltage supply and a common winding (pins1, 2, and 3) to provide the low voltage outputs.Both low voltage outputs use voltage doubler typerectifier arrangement to obtain their outputs. Thehigh voltage rectifier arrangement is a voltagetripler.

2-4 Change 1

TM 11-6665-245-34

Figure 2-5. Discriminator Buffer-Inverter Circuits.

Figure 2-6. Count Rate Circuit Simplified Schematic Diagram.

2-5

Figure 2-6.

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2-6

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CHAPTER 3MAINTENANCE

Section I.

3-1 Maintenance Proceduresa. Location of Troubles. The location of

troubles begins with the gathering of symptoms.Then, with knowledge of the equipment function-ing, a determination can be made as to what sub -system is defective. From that point, more symp-toms are taken, usually with the use of test equip-ment and further determination can be made untilthe faulty component is located. This process iscalled localization and isolation and is thegeneral troubleshooting procedure that should befollowed to locate troubles.

b. Gathering Symptoms. The skill of gatheringsymptoms is learned from experience on theequipment. Without this skill, it is best to follow aset procedure based on the following:

(1) Make a quick. visual check of theequipment to try and spot obvious troubles quick-ly rather than as a result of a lengthy testing ortroubleshooting procedure. Use the quick visualcheck at each stage of the disassembly of theequipment, not just at the start of the procedure.

(2) Do the easy things first. Check for:blown or missing fuses; bad power cables andconnectors; make the checks which are simpleand fast to do.

(3) Perform an operating procedure toquickly check all controls, switches, and in-dicators. In the case of the radiacmeter, theoperational test (para. 3-5) should provide quicksymptoms of trouble. If it doesn’t, perform all thetests in paragraphs 3-12 through 3-14. If no symp-toms appear, the equipment does not contain anyfaults.

c. Repair of Equipment. Repair of the equip-ment in most cases will ‘probably be the exchang-ing of defective parts, printed wiring boards, orassemblies with new ones. Procedures for replac-ing the radiacmeter assemblies are contained in

paragraphs 3-6 through 3-12. The extent of furtherrepa i r d e p e n d s u p o n t h e e q u i p m e n t ’ smaintenance concept as presented in theMaintenance Allocation Chart (TM 11-6665-245-12)and t h e r e p a i r p a r t s a v a i l a b l e ( T M11-6665-245-23P). Certain parts can be replacedwithout affecting the equipment’s calibration,while adjustments must be made when otherparts are replaced. After a repair is made, andprior to testing, check in paragraphs 3-15 and 3-16to find out if adjustments are necessary.

GENERAL

d. Testing Repaired Equipment. Once theequipment fault has been located and corrected,the equipment should be put through a series oftests to determine if it is ready to be returned toservice. The complete test for the radiacmeter iscontained in paragraphs 3-13 through 3-16. Per- f o r m a l l p r o c e d u r e s c o n t a i n e d i n t h o s eparagraphs after repair of the equipment.

e. Precautions. Certain precautions should beobserved while working on the radiacmeter. Theprecautions concern possible injury from elec-trical shock and damage to the photomultipliertube when it is exposed to light.

(1) High voltage of approximately 950volts is used to energize the photomultiplier tubecontained in the probe handle. The high voltage isgenerated on the radiacmeter printed circuitboard and transmitted through the coil cord to theprobe handle. Be sure to locate the high voltagepoints on the printed circuit board (PCB) prior toenergizing the equipment when troubleshooting.

(2) The photomultiplier (PM) tube must beprotected from bright light when the equipment isoff. When the equipment is on, no unintendedlight should be allowed to touch it. Under someconditions, light will either damage the tube orreduce its operating life.

f. Measuring the High Voltage. The powersupply which produces the -950 used for thephotomultiplier tube circuit has a very high inter-nal impedance. This presents a problem when try-ing to make voltage measurements using conven-tional meters. This is because the amount of cur-rent drawn by a conventional meter will reducethe voltage being measured. In order to get an ac-curate reading, a meter that draws no current(electrostatic voltmeter) or very little current (highinput impedance vacuum tube voltmeter) shouldbe used. When those types of meters are notavailable, use a conventional meter, but realizethat the voltage value read has been reduced,possibly up to several hundred volts, from the ac-tual value.

3-2. Maintenance DataMain tenance da ta in th is manua l fo r theradiacmeter includes: schematic and wiring draw-ings, (Figures 3-1, FO-1, and FO-2); parts locationillustrations (Figures, 3-2 and 3-4 through 3-8); andvoltage waveform data (Figures 3-3 and 3-8).

Change 1 3-1

Figure 3-1.

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3-2

C

ha

ng

e

1

Figure 3-2.

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3-3

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Figure .3-3. Voltage Waveforms.

3-4

3-3. Troubleshooting ChartBesides the maintenance data (para.for fault location, a troubleshooting

TM 11-6665-245-34

the test or inspection locates a failure. Retest to

3-2) provided determine if the symptom (malfunction) has been

chart, Table corrected.

3-1, is also included. The troubleshooting chartprovided is made up from typical or expectedtroubles. The chart is organized to present firstthe symptom (malfunction) of the trouble; the testor inspection which should be logically made as aresult of the symptom (malfunction); and the cor-rective action required to correct the malfunction(symptom). The way to use this chart is not to gothrough it step by step, but to look for the symp-tom which closely matches the particular one youare trying to correct. Once the symptom has beenselected, make the tests or inspections indicated.The corrective action should be completed when

Malfunction

3-4. Equipment Required forMaintenance .

The tools and general test equipment required formaintenance are listed in the MaintenanceAllocat ion Chart (MAC)11-6665-245-12. There arequired for maintenance.

con ta ined in TMno special tools re-

3-2) is designed as a3-5. Operational TestThe operational test (tablequick check of the equipment for the repair per-son to use in developing symptom. If the equip-ment passes the test, you can be pretty well

Table 3-1. General Support Troubleshooting Chart

1. Meter scale does not change whenselector switch is moved through itspositions.

2. Meter needle reads upscale when noradioactive source is near probe win-dew.

3. No meter readings on any range whencheck source is placed across probewindow area.

4. No meter readings on one range whenthe check source is placed acrossprobe window area. Other ranges in-dicate normally.

5. No audio output at headphones on anyrange when check source is appliedto probe window. Meter readings arenormal.

6. No meter readings or audio is heard onany ranges.

Test or inspection

a. Inspect selector switch know to be sureits firmly held on to the selectorswitch shaft.

b. Remove radiacmeter panel and ex-amine linkage from meter to selectorswitch while moving the selectorswitch through its positions.

a. Probe may possibly be contaminatedwith radioactive materials. Use aknown good AN/PDR-56F and checkfor contamination.

b. Inspect for probe window light barrierpuncture by passing light over theprobe window area. Use just enoughlight to produce meter indication.

a. Connect earphones and listen for clicks

b. If

on all ranges. If clicks are not heard,suspect a faulty coil cord, and try towork the cord into different posi-tions with both hands while wat-ching for a normal meter reading.

clicks are heard on the earphoneswithout a meter indication, suspecteither a faulty meter switch, faultymeter, or wiring problems.

Examine swi tch S1 f ront and backwafers. Look for bent or loose con-tacts. Check for signal path throughswitch in the bad range using con-tinuity function of multimeter.

Check continuity from center electrodeof phones jack to pin 11 of U1. If con-tinuous, suspect faulty U1. If open,suspect faulty connector P1 on circuitboard.

Check low voltage supply readings. Ifeither voltage is missing or half value,suspect open diodes CR9 thru CR12.Check each diode for proper front to backresistance ratio.

Corrective action

Tighten loose setscrews on linkageor knob.

a. Decontaminate probe.

b. Change light barrier.

a. Replace faulty cord.

b. Replace faulty meter.

Replace or repair faulty meter wafer.

Replace U1 or P1.

Replace faulty diode.

Change 1 3-5

TM 11-6665-245-34

Table 3-2. Operational Test

Procedures

NOTEProcedures 1 through 7 must be repeated for eachprobe.

1. Set selector switch in the following positions in sequence.

a. BATT

b. 1M

c. 100Kd. 10Ke. 1K

2. Disconnect handles and place probe window on checksource.

3. Set selector switch to 10K and press METER RESETpushbutton immediately on changing scales.

4. Connect headphones to panel connector and listen whilemoving source back and forth on probe window to max-imize needle indication.

5. Remove headphones and then set selector switch to 100Kposition.

6. Switch to 1M position.

7. Allow light to hit probe window area while watching meterneedle. If needle goes upscale, immediately cover pro-be window area, removing light. If needle does not goupscale, increase light to window area.

8. Press meter light switch on handle while watching for lightat top of meter scale.

Normal Results

a. Meter scale (change window) shows OFF-BATT. Needle in-dicates in the BATT area.

b. Meter scale shows red, 1 M scale. Needle is at zero after 1 or 2seconds.

c. Meter scale shows orange, 100K scale. Needle is at zero.d. Meter scale shows magenta, 10K scale. Needle is at zero.e. Meter scale shows yellow, 1 K scale. Needle is at zero.

Meter needle pegs upscale.

Meter needle moves to zero when METER RESET switch is helddown; moves upscale when METER RESET switch is released.

Clicking in headset can be heard to increase and decrease withneedle swing.

Needle moves downscale to very low reading.

Needle moves to zero or very low scale reading,

CAUTIONBe careful when allowing light to fall on bottom ofmain probe. Do not allow meter needle to peg ordamage to the photomultiplier tube may result.

Needle remains at zero.

Meter lights when switch is held down,

assured that the equipment is working properlyand can go for calibration. If an item or functionfails the test, this will then develop symptom or acombina t ion o f symptoms to use in thetroubleshooting table 3-3. To use the table, followthe directions in the procedures column to obtainthe results in the normal results column. Start

first by installing two good batteries. Be careful tokeep probe window area shaded from light afterthe equipment is turned on. If main or x-ray probe light barrier is damaged, photomultiplier tube maybe destroyed from excess current. The auxiliaryprobe is tested using a light source to find lightleaks rather than an electrical test as done withthe main probe.

Section Il. REPAIR OF RADIACMETER

3-6. Removal and Replacement of CoverAssembly (Figure 3-4)

The cover assembly of the radiacmeter consistsof the meter panel and all mounted hardware in-cluding the printed circuit board and electronicsinside the case. In order to remove and replacethe cover assembly, simply loosen the six screwswhich hold the panel and case together.

3-7. Removal and Replacement of PCBAssembly (Figure 3-4)

a. Loosen six screws on the radiacmeter untilthe panel and case can be separated. The selectorswitch must be in the OFF position.

b. Remove connector J2 that connects thewiring harness to the PCB by grasping the con-nector with the thumb and forefinger and pullingthe connector.

3-6 Change 1

away from the board. The pull must be straight.c. Remove the four screws that attach the PCB

to the main panel of the radiacmeter.d. Lift the PCB up from the selector switch, and

away from the main panel. Use extreme caution notto break the switch.

e. Install a new PCB using the reverse procedureof (a) through (d) above. Use extreme caution wheninstalling the new PCB on the shaft of the selectorswitch. Alignment of the wafer switch to the shaftmust be exercised with great care. Replace screwsand connector.

3-8. Removal and Replacement ofMeter Light Assembly and Meter

(fig. 3-4)

a. Meter Light Assembly. Replacement of themeter illumination lamp bulb is accomplished asfollows:

(1)(2)(3)

holding(4)

Open the radiacmeter.Remove the A2 printed circuit board.Remove two screws and two large spacersthe meter assembly in place.Note the position of the meter coupling on

the rear of the meter. Loosen the meter couplingscrew and lift the coupling off the rear of the meter.This must be done with care and without undueforce so as not to damage the coupling or the meter.

(5) Loosen the screw at the top of the meterassembly that is used to mount the meter illumina-tion lamp, DS1, to the assembly. Be careful not tobreak the meter wire during this operation.

(6) Swing the small lamp bracket so that thelamp is fully exposed.

(7) Push the lamp out of its mounting from thefront of the meter assembly panel.

(8) Install a new lamp by reversing the pro-cedure.

b. Meter Replacement. Replacement of the in-dicating meter is accomplished as follows:

TM 11-6665-245-34

(1) Remove A2 PCB as outline in paragraph3-7.

(2) Using 3/32 inch allen wrench, loosen thescrew on the flag clamp and the switch clamp. Slideassembly and remove from meter.

(3) Unsolder meter wires. Observe wire colorand polarity.

(4) Remove the two front hex spacer posts.(5) Remove the two rear screws holding meter

plate. Retain two rear spacers for reassembly.(6) Unscrew four screws holding meter to

plate. Retain all hardware for reassembly.(7) Reassemble new meter in reverse order.(8) Turn S1 to OFF position, reset meter flag

to OFF-BATT. Reset clamps and tighten setscrews.(9) Check scale registration on all ranges and

trim meter flag as necessary using long nose pliers.

3-9. Repair and Replacement of SourceAssembly

(fig. 3-4)WARNING

Radioactive material used in the sourceassembly can be dangerous if it is broken in-to small pieces that can be inhaled or in-gested. Serious injury can result if thesesmall particles get into the body. Be carefulwhen removing and replacing the sourcematerial. All broken pieces should be ac-counted for and placed in a sealable con-tainer.

a. Remove the source frame which protects thesource. Use a putty knife to pry up one edge andthen pull the frame from the bottom of theradiacmeter case.

b. Remove the source material by using the sameprocedure as used to remove the source frame.

c. Clean the bottom of the case using a suitablesolvent.

d. Install a new source and source frame. Usepliobond and cement to the bottom of the case.

Section Ill. REPAIR OF PROBES

3-10. Repair of Main Probe and EmitterFollower

(3) Detach thehousing plate of theseparate the bottom

a. Light Pipe and Screen. The replacement of the housing.light pipe or screen is accomplished as follows:

(1) Remove the two screws attaching the emit-ter follower to the light pipe assembly.

(2) Firmly grip the emitter follower housing inone hand and the light pipe assembly in the otherand pull away from each other. It is preferred thatthe dismantling of these two units be done in an ex-tremely dark area so that the photo multiplier tubeis not exposed to light.

six screws from the bottomlight pipe assembly. This willarea of the light pipe from the

(4) Remove the two screws from the light pipe.(5) Lift the light pipe and screen up and away

from the housing plate. Care should be taken not todamage the scintillation screen when removing itform the housing plate.

(6) Align the rubber gasket to the bottomhousing plate.

(7) Install new screen assembly or light pipe tothe housing plate by using the reverse procedure.

3-7

TM 11-6665-245-34

Figure 3-4. Radiacmeter, Exploded View

3-8

TM 11-6665-245-34

Figure 3-5. Main Probe, Exploded View.

Figure 3-6. Aux Probe, Exploded View

Change 1 3-9

TM 11-6665-245-34

b. Emitter Follower and PM Tube Replace-ment. Replacement of the emitter follower is ac-complished as follows:

(1) Disconnect the coil cord from theemitter follower.

(2) Remove the emitter follower handle byturning the handle until the slot is free from theemitter follower pin. Lift the handle off the emitterfollower.

(3) Remove the two screws that connectthe emitter follower to the light pipe and screenassembly.

(4) Firmly grip the emitter follower in onehand and with the other hand, pull the main probeassembly away.

(5) Remove the photomultiplier tubeslowly and carefully from its socket. Caution mustbe taken when handling this tube to prevent thebending or breaking of the tube pins or keyway.

NOTEWhen handling the photomultipliertube, do not touch the tube envelope.Handling will create unstable readingwhen the tube is remounted “for use. Tocorrectly handle this tube, grasp it onlyby its phenolic base. .

(6) Discard the old emitter follower sinceit is unrepairable.

(7) With a new emitter follower, replacethe photomultiplier tube, making certain that thekeyway of the tube socket is properly aligned.

(8) Remount the emitter follower by usingthe reverse procedure.

3-11. Repair of the Aux Probe(Figure 3-6)

The aux probe is repaired by replacing a defectivecover assembly. The cover assentbly is held ontothe probe with four screws (Figure 3-6). There areno other repairs. If the aux probe cannot berepaired with the cover assembly replacement,the complete aux probe will have to be replaced.

3-12. Repair of X-Ray Probe(Figure 3-7)

a. To perform maintenance or repair of thex-ray probe, proceed as follows initially:

CAUTIONHandle scintillation crystal assemblycarefully so as to prevent damage tomylar window.

(1) Remove cap ring assembly from probehousing and then remove jamb ring and scintilla-tion crystal assembly.

NOTEWhen replacing scintillation crystalassembly, you must reseal it to end ofPM tube with optical grease to allowproper optical coupling.

(2) Unscrew the end cap (near the handle)from the probe.

(3) Remove the connector nut from theconnector and depress the connector into the pro-be housing.

(4) Remove retaining ring from probe witha retaining ring extractor.

CAUTIONHandle PM tube gently when removingto prevent damage. Do not touch thesides of the PM tube. Touching thesides can create unstable readingswhen the tube is remounted for use.

(5) Slide assemblies out of the housingby pushing gently on the PM tube from the capring end of the housing.

b. Removal and Replacement of PM Tube(Figure 3-7)..

CAUTIONHandle PM tube gently when removingto prevent damage. Do not touch thesides of the PM tube. Touching thesides can create unstable readingswhen the tube is remounted for use. Donot twist PM tube when removing fromsocket to prevent damage to pins, keyor keyway.

(1) Pull the PM tube straight out of itssocket, slowly and carefully.

(2) Replace the PM tube, making certainthe keyway of the tube socket is aligned with thekey of the tube.

c. Removal and Replacement of the PrintedCircuit Board (Figure 3-7).

(1) Remove PM tube (para. 3-12. b).(2) Remove set screws from tube socket

clamp.(3) Using a heat sink, unsolder leads from

PCB to tube socket and to connector, marking thelocation of each lead.

(4) Slide PCB out of the tube socketclamp.

3-10 Change 1

TM 11-6665-245-34

(5) Slide replacement PCB into tube (2) Using a heat sink, unsolder tubesocket clamp and reverse process of c.(1) and c.(2) socket assembly leads from PCB.above. (3) Replace or repair tube socket, then

d. Replacement of Tube Socket Assembly. solder leads back onto PCB.(1) Remove PM tube from tube socket e. Replacement of Non-Electronic Parts.

(para. 3-12. b). Replace all remaining parts in kind since they arenon-repairable.

Section IV. TESTING REPAIRED EQUIPMENT

3-13. Source Testa. Remove the main probe “window” protec-

tive cover.b. Set the radiacmeter selector switch to 10K.c. Uncoup le the ma in p robe f rom the

radiacmeter and position it against the checksource on the radiacmeter case bottom.

d. Meter should read 6000 & 1200 cpm if thesource is to be considered serviceable.

3-14. Light-Leak Testa. Main Probe.

(1) Remove the main probe “window”protective cover.

(2) Set radiacmeter main probe down on aflat surface so that the “window” is covered.

(3) Set the selector switch in the 100Kposition.. (4) Pick up the main probe and slowly ex-

pose it to light while watching the meter. If themeter reading begins to rise when the probe faceis exposed to light, immediately remove the probefrom the light.

(5) There should not be any meter indica-tion when the probe is exposed to light.

b. Aux Probe. Test the aux probe light barrierfor light leaks by inspection rather than the elec-trical method used for the main probe (a. above).Use a suitable light source (flashlight or handlamp) in a darkened room and direct the light onone side of the probe barrier while inspecting forlight leaks on the other. As an alternate method,remove the four screws (Figure 3-6) that hold thecover assembly to the aux probe chamber and in-spect the cover assembly for light leaks with astrong light.

c. X-Ray Probe.(1) Connect the x-ray probe to the

radiacmeter.(2) Cover the window of the x-ray probe to

prevent entry of light.(3 ) Se t the se lec to r sw i tch on the

radiacmeter to the 1K position.(4) Pick up the x-ray probe and slowly ex-

pose it to a suitable light source (flashlight orhand lamp) while watching the meter.

(5) The meter indication should not riseabove 250 cpm. If the meter reading exceeds 250cpm, immediately remove the probe from the lightsource.

3-15. Calibration of the RadiacmeterThe radiacmeter is calibrated with the main probeattached (the aux probe is not calibrated) usingRadiac Calibrator AN/U DM-7C. Prepare theradiacmeter by installing batteries (selectorswitch: OFF) and removing the cover. Locate thetwo adjustable potentiometers R18 and R26 andthen proceed below:

a. Check the mechanical zero of the meterand adjust if necessary.

b . T u r n R 1 8 ( l e v e l c o n t r o l f u l l ycounterclockwise.

WARNINGHigh voltages are exposed when theradiacmeter case is removed and theequipment is turned on. Locate the highvoltage points on the circuit boardBEFORE truning the radiacmeteron. Becareful to avoid contact with the ex-posed high voltage while making ad-justments. Injury from electrical shockmay result from touching high voltage.

c. Set selector switch to 10K position. Metershould read upscale a s-mall amount. Adjust R18clockwise to reduce the meter reading to zero.

d. Refer to TM 11-6665-247-10 (AN/U DM-7C) forinstructions on setting up the AN/U DM-7C forcalibrating the AN/PDR-56F.

NOTE

e.

Always use the instruct ion in TM11-6665-247-10 for setting up or packingaway the calibrator.

Set up the calibrator using attenuator #1and source A. Remember to remove the main pro-be window guard from the main probe before set-ting it in the AN/U DM-7C probe positioner.

Change 1 3-11

TM 11-6665-245-34

f. After the calibrator is set up and the mainprobe is in position, set the radiacmeter selectorswitch to 100K position.

g. Set R26 (cal. control) so that the meterreading for the 100K scale is the same value aslisted on the calibration report for the AN/UDM-7C.

h. Set up the calibrator using source A only.Then set the radiacmeter selector switch to the1M position and place the main probe in positionon the calibrator.

i. The meter reading should be within thelimits specified on the calibration report.

j. Set up the calibrator using source C only.Set the radiacmeter selector switch to the 10Kposition and place the main probe in position onthe calibrator.

k. The meter reading should be within thelimits specified on the calibration report.

l. Set up the calibrator using attenuator #1and source- C. Then set the radiacmeter selectorswitch to the 1K position and place the mainprobe in position on the calibrator.

m. The meter reading should be within thelimits specified on the calibration report.

n. Remove the main probe from the calibrator.The meter reading should go to zero.

o. Set the selector switch to OFF, reassemblethe radiacmeter and put the calibrator away.

p. Connect the headset to the radiacmeterand set the selector switch to the 1 K position.

q. Listen in the headset for clicks caused bybackground radiation. Count the clicks for oneminute. The count should not exceed 15 for 1minute (15 cpm).

3-16. Calibration of the X-Ray ProbeThe x-ray probe is also calibrated using theAN/UDM-7 Pu-239 alpha calibration sources.Before calibrating the x-ray probe, the lM-160F/PDR-56 radiacmeter with the main alpha

probe attached must be calibrated. The x-ray probe is then attached to the radiacmeter aoutlined in para. 2-2. b of TM 11-6665-245-12 Calibration of the x-ray probe is then accom-plished without readjusting the radiacmetercalibration controls or the high voltage setting ofthe radiacmeter. The calibration of the x-ray probinvolves the adjustment of the probe amplifiergain to set the 14-21 keV x-ray photo peak withinthe discriminator window of the single channelanalyzer (SCA). The lower and upper threshold ofthe SCA are fixed at -2.3 volts and -6.0 voltsrespectively and should not need adjustment.Once the amplifier gain is properly set, the x-rayprobe sensitivity factor (cpm/mg/cm2 of Pu-239) isdetermined using the UDM-7B source A.

Prior to a source calibration, ensure that theprobe is functioning. Proceed as follows:

(1) Unscrew the end cap from the probe,exposing the two calibration potentiometers andrelated test points.

(2) Position the phosphor end of probeapproximately one inch from a UDM-7 “A” source.

(3) Turn selector switch to 100K scale.( 4 ) C o n n e c t D i g i t a l V o l t m e t e r o r

Multimeter to Test Point 2 (Figure 3-8) and checkfor -2.3 Vdc ± 0.1 Vdc.

( 5 ) C o n n e c t D i g i t a l V o l t m e t e r oMultimeter to Test Point 3 (Figure 3-8) and adjustR54 for -6.0 Vdc ± 0.1 Vdc.

(6) Connect oscilloscope probe to TestPoint 1 of Figure 3-8 and adjust R49 so that thecenter band of negative pulses is between -3.5and -4 V (refer to wave shape on Figure 3-8).

(7) The meter reading of a properlycalibrated probe should be in the range of 32 to 40K cpm.

(8) Secure the calibration pots with glyp-tol (or equivalent).

(9) Reinstall end cap on the probe.

3-12 Change 1

Figure 3-7.

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Change 1 3-13

Figure 3-8.

TM 11-6665-245-34

3-14 Change 1

TM 11-6665-245-34

APPENDIX AREFERENCES

DA Pam 310-1 Consolidated Index of Army Publications and Blank Forms.

DA Pam 738-750 The Army Maintenance Management System (TAMMS)

FM 21-11 First Aid for Soldiers.

TB 43-180 Calibration Requirements for the Maintenance of Army Material.

TM 11-5965-247-12P Operator and Organizational Maintenance Repair Parts and Special Tools Listand Maintenance Allocation Chart, Headset-Electrical H-43B/U.

TM 11-5965-247-35P Field and Depot Maintenance Repair Parts and Special Tools List, Headset-Electrical H-43B/U.

TM 11-6665-245-12 Operator and Organizational Maintenance Manual, Radiac Set AN/PDR-56F(NSN 6665-00-211-6895).

Change 1 A-1/(A-2 blank)

TM 11-6665-245-34

By Order of the Secretary of the Army:

Official:

E.C. MEYERGeneral, United States Army

Chief of Staff

ROBERT M. JOYCEMajor General, United States Army

The Adjutant General

DISTRIBUTION:

To be distributed in accordance with Special Mailing List.

THE METRIC SYSTEM AND EQUIVALENTS

PIN: 053646-001