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TM 11-6625-524-14-2

TECHNICAL MANUAL

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT,

AND GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST

(INCLUDING DEPOT MAINTENANCE REPAIR PARTS

AND SPECIAL TOOLS)

F O R

VOLTMETER, ELECTRONIC AN/URM-145B(NSN 6 6 2 5 -0 0 -4 3 7 -4 8 6 5 )

This copy is a reprint which includes current

pages from Changes 1. The title was

changed by Change 1,

H E A D Q U A R T E R S , D E P A R T M E N T O F T H E A R M

31 OCTOBER 197



TM 11-6625-524-1

T E C H N I C A L M A N U A L H E A D Q U A R T E R S

D E P A R T M E N T O F T H E A R M

No. 11-6625-524-14-2 W A S H I N G T O N , DC, 31 October 19

OPERATOR’S ORGANIZATIONAL, DIRECT SUPPORT, AND

GENERAL SUPPORT MAINTENANCE MANUAL

C HAPTER 1.

S ECTION I .

S ECTION I I .

C HAPTER 2.

C HAPTER 3.

C HAPTER 4.

C HAPTER 5.

VOLTMETER, ELECTRONIC AN/URM-145B

(NSN 6625-00-437-4865)

Par ag r aph

INTRODUCTION

General

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Indexes of publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .1-2

Form s a nd r ecords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .1-3Administrative storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3.1

Destruction of Army electronics materiel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3.2

Report ing of err ors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .1-4

Reporting Equipment Improvement Recommendations (EIR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4.1

Description and data

Description and use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Technica l cha ra cteris tics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .1-6

Items comprising a n operable equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...1-7

INSTALLATION

Unpacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Checking unpacked equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..2-2

Cable connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

OPERATING INSTRUCTIONS

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Preliminary operating instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Contr ols and indicat ors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3-3

Opera tin g procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

OPERATOR’S AND ORGANIZATIONAL MAINTENANCE

Scope of maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Preventive maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

P reventive maint enan ce checks a nd services periods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-3

Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...4-4

Rustproofing and painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

CIRCUIT FUNCTIONING

Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Rf probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Range selector switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Input filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Dc modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Narrow band preamplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .5-6

Driver and output circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Synchronous demodulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8

Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9

Reference amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Dc feedback and calibration controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Output, linearizing networks, and meter circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Regulated power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

P a g e

1-1

1-1

1-1

1-1

1-1

1-1

1-1

1-1

1-2

1-2

2-1

2-1

2-1

3-1

3-1

3-1

3-1

4-1

4-1

4-1

4-2

4-2

5-1

5-3

5-3

5-3

5-3

5-3

5-4

5-5

5-5

5-6

5-6

5-6

5-7

Change



TM 11-6625-524-14-2

C HAPTER 6.

S ECTION I .

I I .

I I I .

C H A P T E R 7 .

AP P E ND IX A.

B .

AP P E ND IX C .

S ECTION I . In troduct ion

I I .

I I I .

IV.

II . Ma intenance allocation chart

C -1

C -3

C -4

C -5Tool and test equipment requirements

R e m a r k s

Figure No.

1-1

1-2

1-3

2-1

3-13-2

5-1

5-2

5-3

5-4

5-5

5-6

5-7

5-8

5-9

5-10

6-1

6-2

6-3

6-47-1

7-2

7-3

TABLE OF CONTENTS - Continued

Paragraph P a g e

GENERAL SUPPORT MAINTENANCE INSTRUCTIONS

Troubleshooting

Troublesh ooting t echniqu es . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..6-1

Tools and Test Equipment

Tools an d Test equipment r equired for troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...6-2

Troublesh ooting cha rt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..6-3

Signa l tr acing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Dcresista nce of tra nsformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..6-5

Maintenance

Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 6-6

Remova l of pc boar d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..6-7

Replacement of pc board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..6-8

GENERAL SUPPORT TESTING PROCEDURES

General testing procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Test eq uipmen t r equir ed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..7-2

P ower supply t est . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..7-3

Pr eamplifier and a mplifier test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...7-4

Volta ge accura cy test . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

REF ER ENC ES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ORGANIZATIONAL, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE

REPAIR PARTS AND SPECIAL TOOLS LIST (INCLUDING DEPOT

MAINTENANCE REPAIR PARTS AND SPECIAL TOOLS) (Deleted)

MAINTENANCE ALLOCATION

6-1

6-3

6-3

6-3

6-4

6-4

6-4

6-5

7-1

7-1

7-1

7-2

7-2

A-1

LIST OF ILLUSTRATIONS

Title

Voltmet er, E lectronic AN/U RM-145B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input capa citan ce of RF probe (meas ured a t 10 MHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

In put resis ta nce of rf probe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Typical pa ckaging dia gra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Fr ont pa nel contr ols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Rear panel controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Rf probe, simplified schemat ic diagra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Na rrow ba nd prea mplifier, schema tic diagr am . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Driver a nd output, schemat ic diagra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Synchronous demodulat or, simplified schematic diagr am . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Driver, simplified schemat ic diagr a m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reference am plifier, simplified schemat ic diagra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Scale correction netw ork, schema tic dia gra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regulat ed power supply, simplified schema tic diagr am . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Voltm eter, E lectronic AN/UR M-145B , schema tic dia gra m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Voltage an d resistance measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Amplifier boa rd 3A2, locati on of par ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Ca libra tion boar d 3A3, loca tion of par ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regula ted power s upply 3A1, locat ion part s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Power supply test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Preamplifier and amplifier test setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Volta ge a ccura cy tes t s etu p... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

P age

1-0

1-2

1-3

2-1

3-23-3

5-2

5-2

5-4

5-4

5-5

5-5

5-6

5-7

5-7

5-7

6-2

6-5

6-6

6-77-1

7-2

7-3

i Change 1



Figure 1 1.

TM 11-6625-524-14-2

-0 Change 1



TM 11-6625-524-14

CHAPTER 1

INTRODUCTION

1-1. Scope

Section 1.

T h i s m an u a l d e sc r i b e s V o l t m e t e r , E l e c t ron i c

AN/U RM -145B (fig. 1-1) and provides instructions

for operation and organizational, direct support ,

and general support (GS) maintenance. Instruc-

tions are provided for the operator and the organi-

zat ional maintenance personnel for instal lat ion ,

operation, preventive maintenance, and replace-

ment of parts avai lable at organizat ional mainte-

nance. Circuit functioning is included for general

support maintenance, together with instructions

appropriate to this category of maintenance for

troubleshooting, test ing, adjusting, aligning and

repai r ing the equ ipment and rep lac ing main te-

nance parts .

1-2. Indexes of Publications

a. DA Pam 310-4. Refer to the latest issue of DA

Pam 310-4 to determine whether there are new

edit ions, changes or addit ional publicat ions per-

tain ing to the equipment .

b. DA Pam 310-7. Refer to DA Pam 310-7 to de-

termine whether there are Modificat ion Work Or-

ders (MWO’S) pertaining to the equipment.

1-3. Forms and Records

a. Reports of M ain tenan ce and U nsati sfactory

Equ ipment . Maintenance forms, records, and re-

ports which are to be used by maintenance person-

nel at al l maintenance levels are l is ted in and pre-

scribed by TM 38-750.

b. Report of Packaging and H andl in g Deficien-

ties. Fil l out and forward DD Form 6 (Packaging

Improvement Report) as prescribed in AR 700-

5 8 /N A V S U P I N S T 4 0 3 0 . 2 9 /A F R 7 1 -1 3 /M C O

P4030.29A, and DSAR 4145.8.

G E N E R A L

c. Discrepancy in Shipment Report (DISRE

(SF 361) . F i l l ou t and forward Discrepancy

Shipment Report (DISREP) (SF 361) as prescrib

in AR 55-38/NAVS U P INS T 4610.33A/AFR 75-1

MCO P 4610.19B, a nd D SAR 4500.15.

1-3.1. Administrative Storage

Administrat ive storage of equipment issued to a

used by Army activit ies shall be in accordance wi

TM 740-90-1.

1-3 .2 . Dest ruct ion of Army Elect ronic

Materiel.

Destruction of Army electronics materiel to pr

vent enemy use shall be in accordance with T

750-244-2.

1-4. Reporting of Errors.

You can help improve this manual by calling at te

t ion to errors and by recommending improvemen

and stat ing your reasons for the recommendation

Your le t t e r or DA Form 2028 (Recommend

Changes to Publicat ions and Blank Forms) shou

be mailed direct to Commander, US Army Ele

t ron ics Command , ATTN: DRSEL-MA-Q, Fo

Monmout h, New J ersey 07703. A reply w ill be funished direct to you.

1-4.1. Reporting Equipment Improveme

Recommendations (EIR).

EIR’s will be prepared using DA Form 2407 (Mai

t e n a n c e R e q u e s t ) . I n s t r u c t i o n s f o r p r e p a r i n

EIR’s are provided in TM 38-750, The Army Mai

tenance Management Sys tem. EIR’s shou ld b

mailed direct to Commander, US Army Electroni

C o m m a n d , A T T N : D R S E L - M A - Q , F o r t M o

mouth, New J ersey 07703. A reply w ill be furnish

direct to you.

Section Il. DESCRIPTION AND DATA

1-5. Description and Usefor many associated tests . Such measurements i

clude the frequency response of both active a

a. Voltm eter , Elect roni c AN/U RM-145B (voltm e- passive networks; that is, amplifiers, and filte

ter) is a sensit ive instrument for the measurement voltage standing wave rat io (vswr) ant i re turn lo

of voltages of 300 microvolt (uv) to 3 volts span- on t ransmission l ines and at tendant systems;

ning a frequency range of 20 kilohertz (KHz) to 600 tenuat ion and insert ion loss of r f at tenuators ; a

megaher t z (MHz) . In add i t ion to conven ien t ly h igh f requency parameters o f t rans is tors . Wi

measuring voltage levels in a diversity of radiofre- true root mean square (rms) response below 0.

quency (rf) circuits, the instrument has applicat ion volt , wide hand noise can be measured, and by u

Change 1 1



Figure 1 2.

TM 11-6625-524-14-2

of su i t ab le nul l ne tworks , measurement o f the

harmonic distortion of rf waveforms can be per-

formed wi thout the a t tendant errors of average-

type meters. The voltmeter is also useful as an rf

n u l l d e t e c t o r f o r b r i d g e m e a s u r e m e n t s a n d

analogous techniques when a sensitivity in the

order of 200 uv will suffice.

b. Supplied with each instrument is a general

purpose rf probe, 50-ohm adapter and probe tip.The adapter is fi t ted with a type bnc coaxial con-

nector and provides a 50-ohm termination with a

low vsw r up to 600 MHz . The probe tip is u seful for

direct measurement to approximately 250 MHz.

However, a short wire should be substi tuted for

the ground lead when using above 100 MHz to

minimize the effects of ground lead inductance.

Above 250 MHz, the probe may be used directly

without the tip, but the connecting leads must be

extremely short to avoid resonant effects. Nor-

ma lly, the rf probe is used w ith t he 50-ohm ad a pter

in a coaxial system for accurate measurementsabove 100 MHz.

c. The rf probe with its full-wave crystal detect-

ing circuit produces a true rrns response without

turnover, or harmonic errors for all voltage levels

below 0.03 volt, gradually changing to peak-to-

peak reading (calibrated in rms) at approximately

1.0 volt. The probe has a shunt capacitance of ap-

proximately 2.2 water holding energy (pF) at levels

of 0.3 volt or higher, decreasing slightly at levels of

0.1 volt or less (fig. 1-2). The shunt resistance com-

ponent shown in figure 1-3 is a variable factor,

depending on the voltage and frequency. A decibel

(db) scale in red on the panel meter and rangeswitch provides a convenient means of expressing

relative voltage measurements.

d. A screwdriver zero control on front of the

meter provides zero adjustment of the meter

pointer.

e. The main controls required to operate the

voltmeter are on the front panel. Several minor

controls are on the rear panel.

1-6. Technical Characteristics

Measur ement ra nge 300 uv to 3 volt.

Frequency ra nge .20 KH z to 600 MHz.

Full scale ranges . . . . . . . . 0.001.0.003.0.01, 0.03,0.1,

0.3, 1.3 volt.

Accuracy . . . . . . . . . 0.001 range 10 percent of

only full scale to

200 MHz

15 percent of

full scale

above 200

MHz.

0.00:3 range and 5 percent of full

above scale to 200

MH z

10 percent of

full scale

above 200

MHz.

Input inpedance . . . . . . . .See figure 1-3.

Decibel range (red scale) . ..0 to 70 db in 10 db steps.

Maximum vswr . . . 1.2 up to 600 MHz.

P ower r equir ement s . ...115/230 volt, 55 to 65 Hz . 12

wa t t s .

Dimensious . . . . . . . . . . . . . . . .9 inch H x 6½ inchW x 11¼

inch Doverall (handle

folded).

Weight . . . . . . . . . . . . . . . . . . .. 10lb.

1-7. Items Comprising an Operable Equip-

ment

a. Voltm eter , E lectronic ME -247C/U .b. P robe, P /N 900-2000B .

c. 50-ohm Adapt er, P IN 900-2050A.

d. P robe t ip, P /N 900-2002.

e. P ower cord, P /N 800-5121.

f. output plug, Sw itchcraft Inc., P /N 60.

1-2 Change 1



Figure 1 3.

TM 11-6625-524-14



TM 11-6625-524-14-

CHAPTER 2

I N S T A L L A T I O N

2-1. Unpackinga. Packaging Data. When packed for ship-

ment , Voltmet er, E lectron ic A-N/U RM - 145B is

placed in a waterproof carton and packed in a

corrugated cardboard box. A typical packing case

and its contents are shown in figure 2-1.

b . Remo v i n g Co n t e n t s . P e r f or m a l l t h e

procedures in (1) through (4) below when un-

packing equipment.

(1) Open the outer corrugated carton and

moistureproof barrier.

(2) Remove the inner carton.

(3) Open the inner corrugated carton.

(4) Remove the voltmeter.

2-2. Ch ecking Unpacked Equipment

a. Inspect the equipment for damage incurred

during shipment.

b. Check to see that the equipment is complet(paragraph 1-6). Report all discrepancies in ac

cordance with TM 38-750. Shortage of a mino

assembly or par t tha t does not a f fec t p rope

functioning of the equipment should not preven

use of the equipment.

c. If the equipment has been used or recon

dit ioned, see whether it has been changed by a

modif icat ion work order (MWO). I f the equip

ment has been modified, the MWO number wil

appear on the side near the nomenclature. Check

to see whether the MWO number (if any) and

ap p rop r i a t e n o t a t i on s c on c e rn i n g t h e m od i

f i c a t i on h av e b e e n e n t e re d i n t h e e qu i p m e nmanual .

NOTE

C u r r e n t M W O ’s a p p l ic a b l e t o t h e

equipment are listed in DA Pam 310-7.

Fi gure 2-1. Typical packaging diagram.

2-3. Cable Connections d. Screw the probe tip on the rf probe for direct

Connect the cables and adapters as follows: measurements up to 100 MHz. Above 100 MHz,

a. Insert the power cord plug into the three- the probe may be used without the t ip.

prong receptacle on the rear panel.

b. Insert the rf probe plug into the receptacleCAUTION

on the front panel.Above 250 MHz, connecting leads must

c. Screw the 50-ohm adapter on the rf probeb e e x t re m e l y sh or t t o av o i d re son an t

when a 50-ohm termination is required. effects.

2-1



TM 11-6625-524-14

CHAPTER 3

O P E R A T I N G I N S T R U C T I O N S

3-1. General 3-2. Preliminary Operating InstructionsThis section should be read carefully before using a. Set 115/230 volts sw itch, on t he rea r pa nethe voltmeter. I t contains information necessary for the input voltage to be used.for proper operation of the voltmeter. To achieve b. S e t L I N E sw i t c h a t O F F .v a l i d r e a d i n g s , proper s w i t c h s e t t i n g s a r e c. Turn the adjusting screw on the front panrequired. C o n t r o l s a n d i n d i c a t o r s , w i t h t h e meter until the pointer is at SET REF.funct ion of each, are l is ted in paragraph 3-3.

Operating procedures are described in paragraph

3-4. The controls are shown in figures 3-1 and 3-2.

3-3. Controls and Indicators

The controls for the voltmeter are on the front an

rear panels. Their functions are described in t ab

3-1.

Tabl e 3-1. Controls and Ind icators

Control or indicator

Range selector switch

SET REF control. . .

LINE switch . . . . . . . . . .

LINE lamp..

P R O B E c o n n e c t o r .

Mechanical zero adjust screw (rear panel controls).

DC OUTPUT jack . . . . . . . . . . . . . . . . . . . . . . . . . . .

P OWER connector . . . . . . . . . . .

115/230 VOLTS sw it ch

3-4. Operating Procedures

Function

a. Genera l . Be fore opera t ing the vol tmeter ,

check the meter to see if the pointer falls on the

SET REF mark. It it does not , turn the SET REF

control until the pointer is exactly over the SET

REF mark. At the low end of the 0.001 scale of

the meter, 100 uv and 200 uv points are provided.

These are designated by the small numerals 1 and

2 and should be used only on this r a nge.

CAUTIONDamage to the d iode car t r idge in the

probe may result if the input exceeds 500volts dc or 40 volts peak-to-peak.

b. M easur ement Pr ocedu r e.

(1) Set LINE switch to ON.

Selects one of eight voltage ranges.

Adjusts the meter pointer to the reference point with zero

input signal. Should perferably be adjusted on the lowest

range.

A two position ON-OFF switch. Connect AC power to the

voltmeter at the ON position.

Indicat es that ac power is applied when l i t .

A nine pin receptacle which accepts the rf probe connector.

Provided for mechanical zero adjustment of the meter pointer.

A tip, ring, sleeve phone-type jack for dc output.

A three pin receptacle which accepts the power cord connector.

Selects tr an sformer connections for 115 or 230 volts input.

(2) Connect the probe tip to the probe fo

direct measurement or the 50-ohm adapter fo

measurements in 50-ohm systems or above 10

MHz. Above 250 MHz, the probe may be use

directly without the adapter.

( 3 ) I f t h e a p p r o x i m a t e v o l t a g e t o b

measured is known, set the range selector switc

to the appropriate scale. Otherwise, set switch a

3 volts scale and turn switch to lower scales unt

a proper meter reading is obtained.

(4) To obtain readings in db, add db mete

reading (red scale on meter) to the db setting the range selector switch.

3



Figure 3 1.

TM 11-6625-524-14-2

3-2



TM 11-6625-524-14

Fi gu r e 3 -2. Rea r pan el con t r o l s.

WARNING measur ing low level r f vo l t ages , a lways t a

Do not exceed 5W r f when using any of the precautions to avoid the possibility of erroneo

adapters wi th the probe. readings resulting from hum, noise, or stray

c. H um , N oise, and Spur ious Pickup. W h e n pickup. Al though al l low frequency hum a



TM 11-6625-524-14-2

noise is attenuated at the input by 60 db, i t is sti l l

possible for high level unwanted signals to get

through and cause errors. The best test for this

condition is to reduce the test signal to zero level

and note whether the voltmeter continues to read

some spurious signal level. In some cases, extra

shie ld ing may be necessary a round the probe

connections to reduce stray field pickup. Typicalsources of spurious radiat ion are induct ion or

die lec t r i c hea t ing uni t s , d i a thermy machines ,

loca l r adio t r ansmi t ters , gr id d ip meters , and

amplifiers with parasitic oscil lations.

d. M agneti c Field s. Operation of the voltmeter

in strong 60 Hertz (Hz) magnetic fields, such as

t h o s e-

su rr ou nd in g u n s h ie ld e d p ow e r t r ans-formers, should be avoided. The magnetic field

induces small 60 Hz currents in the amplifier

section of the instrument which, due to the ex-tremely high gain at this frequency, appear as an

indication on the meter.

3 - 4



TM 11-6625-524-1

CHAPTER 4

O P E R A T O R ’ S A N D O R G A N I Z A T I O N A L M A I N T E N A N C E

4-1. Scope of Maintenancea. Th e m a i n t e n a n c e du t i e s a s s i g n e d t o t h e

operator of the voltmeter are l isted below together

with a reference to the paragraphs covering the

specific m a i n t e n a n c e f u n c t i o n s . T h e d u t i e s

assigned do not require tools or test equipment

other than those issued with the equipment.

(1) Cleaning (para 4-4).

(2) Rustproofing and paint ing.

b. Th e m a i n t e n a n c e du t i e s a s s i g n e d t o t h e

o r g a n i z a t i o n a l m a i n t e n a n c e r e p a i r m a n o f t h e

v o l t m e t e r a r e s h o w n i n table 4-1. The dut ies

assigned do not require tools or test equipment

other than those issued with the equipment.

4-2. P r event ive Maintenance

Prevent ive maintenance i s the sys temat i c care ,

s e r v i c i n g , a n d i n s p e c t i o n o f t h e e q u i p m e n t t o

prevent the occurrence o f t roub le , to reduce

downt ime, and to assure tha t the equipment i s

serviceable. The procedures given in table 4-1

c o v e r r o u t i n e s y s t e m a t i c c a r e a n d c l e a n i n g

essential to proper upkeep and operation of the

equipment .

4-3. Preventive Maintenance Checks and Ser-

vices PeriodsPrevent ive maintenance checks and services of

t he AN/U RM -145B/U a rer e q u i r e d d a i lweekly, monthly, and quarterly as shown in tab

4-1 and under the special conditions listed belo

a. Before the voltmeter is taken on a missio

b. When the vol tmeter is ini t ia l ly insta l le

c. Wh e n t h e v o l t m e t e r i s r e i n s t a l l e d a f t

removal for any reason.

d. At least once a week, if the equipment

mainta ined in s t andby condi t ion . Per form th

m a i n t e n a n c e f u n c t i on s i n d i ca t e d i n t h

organiza t iona l monthly prevent ive maintenan

checks and services table once each month.

month is defined as approximately 30 calend

days of 8-hour-per-day operat ion. I f the equiment i s opera ted 16 hours a day , the month

p r e v e n t i v e m a i n t e n a n c e c h e c k s a n d s e r v i c

s h o u l d b e p e r fo r m e d a t 1 5 -da y i n t e r v a l s . A

jus tment o f the maintenance in terva l mus t b

made to compensa te for any unusua l opera t in

condi t ions . Equipment mainta ined in a s t and

(ready for immediate operat ion) condi t ion mu

have monthly preventive maintenance checks a

services. Equipment in limited storage (requir

service before operation) does not require month

maintenance.



TM 11-6625-524-14-2

W-weekly Q-Quarterly

I tem

Number A

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

lnterva l

Operator

B

x

x

x

x

Dai l y

D

x

x

x

W

x

x

x

Or g.

M

x

x

Q

x

x

x

x

x

x

x—

Ta ble 4-1. Pr event iv e M ai nt enan ce Ch ecks and Servi ces

B - Before Operation A-After Operation M-Monthly

D-During Operation

Item to be Inspected

Voltmeter . . . . . . . . . . .

Exterior surfaces . . . .

E x t e rna l recep t a c l es

Meter glass . . . . . . . . .

Knobs, controls, and

switches

Operation . . . . . . . .

Voltmeter . . . . . . . . . . .

Ca bles . . . . . . . . . . . . . .

Ha rdwa re . . . . . . . . . . .

Preservation . . . . . . .

P ublications . . . . . . . . .

MWO’s . . . . . . . . . . . . . .

Completeness . . . . . . .

Exterior surfaces . . . .

External receptacles.

Preservation . . . . . . . .

M et er g la s s . . . . . . . .

Ca bles . . . . . . . . . . . . . .

Operation . . . . . . . . . . .

Procedure

Check for completeness a nd general

condition.Check exterior surfaces.

Inspect external receptacles for breakage

and looseness.

Inspect gla ss w indow for brea ks, physical

dama ge, dust , or moisture.

During operation, check knobs, controls,

and switches for proper mechanical a ct ion.

Be alert for any abnormal indicat ions.

Check for any peculiar odors which would

indicate overheated components.

Inspect cables for cuts, cracked or gouged

jackets, fra ying, or kinks.

Inspect al l exterior h ar dwa re for looseness

and damage.

Inspect equipment for bare spots, rust a ndcorrosion.

Inspect manua l for completeness an d usa ble

condit ion. B e sure tha t a l l chan ges are on

hand.

Check to see that al l U RG ENT MWO’S

have been applied and that al l NORMAL

MWO’S ha ve been scheduled.

Sa me as i tem 1.

Sa me as i tem 2.

Sa me as i tem 3.

Sa me as i tem 10.

Sa me as i tem 4.

Sa me as i tem 8.

Sa me as i tem 6.

Reference

(Pa ra 4-7).

(Para 4-7 and4-8).

DA Pam 310-4

DA Pam 310-7

4-4. Cleaning when c lean ing ; the meter may become

Inspect the exterior surfaces of the voltmeter. The

exterior sur faces should be free of dirt , grease, a nd

fungus.

a. Remove the dust and other loose dirt with a

clean, soft cloth.

WARNING

The fumes of trichloroethane are toxic.

Provide thorough ven t i l a t ion whenever

used. DO NOT use near an open flame.

Trichloroethane is not flammable, but ex-

posure of the fumes t o an open flam e con-

verts the fumes to highly toxic dangerous

gases.

b. Remove grease, fungus, and ground-in dirt

from the cases; use a cloth dampened (not wet)

with trichloroethane.

c. Remove dirt from plugs and jacks with a brush.

CAUTIONDo not press on the meter face (glass)

damaged .

d. Clean the f ron t pane l meter , and con t ro l

knobs; use a soft , clean cloth. If n ecessary , da mpen

the cloth with water; mild soap may be used for

more effective cleaning.

4-5. Rustproofing and Painting

a. Rustpr oofi ng. When the finish on the voltme-

ter ha s become badly scarred or dama ged, rust a nd

corrosion ca n be prevented by t ouching up t he ba re

spots. Use No. 000 sandpaper to clean the surface

down to the bare metal . Obtain a bright , smooth

finish.

b. Painti ng. Remove rust and corrosion from

metal surfaces by l ight ly sanding them with f ine

sandpaper. Brush two th in coats of paint on the

bare metal to protect it . Refer to the applicable

cleaning and refinishing practices specified in TB

43-0118.

4-2 Change 1



TM 11-6625-524-1

C H A P T E R 5

C I R C U I T F U N C T I O N I N G

5-1. Block DiagramThe basic circuitry of the voltmeter is best un-

derstood by reference to the block diagram (fig. 5-

1).

a. The input signal is sampled and detected by

the rf probe. The direct current (dc) output signal

f rom the probe , a f t e r pass ing th rough the a t -

tenuator section of the range selector switch, goes

through an input filter which rejects power line

f re qu e n c y c om p on e n t s w h i c h m i g h t c au se a

measuring error.

b. A single-pole, double-throw dc modulator

(3G1) then converts the dc signal into a nearly

symmetrical square wave.

c. The square wave is impedance matched and

ampl i f ied by a h igh impedance , narrow band

preamplif ier (3A2Q9 through Q12). I t s narrow

b an d w i d t h a l so i m p rov e s t h e s i g n a l - t o- n o i se—ra t io .

d. The preamplifier output is further amplified

in the driver and output stage (3A2Q13 and

3A2Q14).

e. The alternating current (ac) signal from to u t p u t s t a g e i s r e c t i f i e d b y a s y n c h r o n od e m o d u l a t o r ( 3 A 2 Q 7 a n d 3 A 2 Q 8 ) a n d t

resu l t an t dc ou tpu t i s used to provide hea

o v e r a l l d c f e e d b a c k a n d t e m p e r a t u r e co

pensation. The dc output is also linearized in t

output circuit and connected to the indicat i

meter.

f . The dc modulator output is also connected

a driver (3A2Q1 and 3A2Q2) which drives

reference amplifier (3A2Q3 and 3A2Q4).

g. The output from the reference amplifier

fed to the synchronous demodulator. The pharelat ionship between the reference amplifier a

the input signal determines the polarity of the

ou t p u t w h i c h i s c on n e c t e d t o t h e i n d i c a t i

meter.

h. An electronical ly regulated power supp

(3A1CR1 and 3A1CR2) plus transistors delive

-14.5 volts to the amplifier. The amplif

divides the power supply voltage to - 6 volts a

+ 8.5 volts .



Figure 5 1.

TM 11-6625-524-14-2

Fi gur e 5-2. R f p robe, sim p l i f i ed schemat i c d i a g ra m.

5-2



TM 11-6625-524-1

5-2. Rf Probe

The rf probe (fig. 5-2) contains a diode cartridge

assembly. The cartridge assembly contains acoupling capacitor, two matched diodes, a pair of

filter capacitors and a pellet resistor. The sealed

section of the rf probe housing contains two filter

resistors connected in series with the outputterminals of the diode cartridge, and a tern-

perature sensing thermistor network connected in

the dc feedback loop of the amplifier. The ther-

mistors are connected to the individual ranges bymeans of sections C and E of the range selector

switch 3S2. The individual pins of connector 3J1

are bypassed to ground by filter capacitors and

thus prevent any possible error introduced by

stray rf pickup in the probe cable.

5-3. Range Selector Switch

a. The range selector switch consists of sec-

tions A through H. Sections A and B (range

attenuator) contain resistive dividers supplying

the full or partial voltage to the input of theamplifier. This voltage, when modulated, am-

plified, and demodulated, will indicate on themeter a reading corresponding to the value of theinput signal within the accuracy rating of the

range being used.

b. Section D disconnects 3R55 to provideadditional gain on the two 10 west ranges.

c. Sections C and E, in conjunction withsection H, form part of the dc feedback loop.

Section H contains individual resistors and

potentiometers to control the main feedback loopof each midrange control. The thermistors,located in the rf probe, sense and correct for any

thermal errors occurring as a result of the tem-

perature characteristics of the rf diodes and switched into the circuit through sections C a

E.

d. Sections F and G switch in both resist

and potentiometers for correcting the nonlinea

of the rf diodes.

5-4. Input FilterThe input filter consists of RC networks and

tuned parallel T-network providing an effective

filter with a minimum of 60-db rejection

powerline. frequency.

5-5. Dc Modulator

A 94-Hz printed circuit plug-in dc modula

(3G1), is employed. It modulates the dc in

signal, and the resultant ac component is pedance matched to the narrow band prea

plifier.

5-6. Narrow Band Preamplifier

The narrow band preamplifier features a l

noise, high impedance input achieved by the

of a high quality field effect transistor 13A2QDiodes 3A2CR3 and 3A2CR4 form a clamp cir

to protect the input transistor from excess

overload. A three-stage conventional RC-coupcommon-emitter amplifier, consisting of 3A2QQ11, and Q12, with the input transistor 3A2

develop a gain of approximately 80 db. A tuparallel T-network in a negative feedback lofrom the collector of 3A2Q12 to the base

3A2Q10 narrows the amplifier bandwidth athus improves the signal-to-noise ratio. Tsupply voltage is held at +8.5 volts by Ze

diode 3A2VR1.



TM 11-6625-524-14-2

Fi gure 5-3. Nar row band preampli f ier , schematic di agram.

5-7. Driver and Output Circuit of signal applied to the base of the driver. Am-

The driver (3A2Q13) and output stage (3A2Q14) plifier gain control 3A2R55 is disconnected on the

a r e c o n v e n t i o n a l c a p a c i t o r - c o u p l e d s t a g e s . two lowest ranges to allow additional gain. The

Amplifier gain control 3A2R53 adjusts the level signal developed in the output stage is applied to

the synchronous demodulator.

Fi gure 5-4. D ri ver and output, schemati c diagram.



TM 11-6625-524-14

5-8. Synchronous Demodulator s ignal polar i t y . In th is operat ion the collect

Transistors 3A2Q7 and 3A2Q8 are utilized in this current is a function of collector voltage only, an

phase-sensitive rectifying circuit. The signal from is essentially independent from other transist

the output stage (3A2Q14) is compared with the parameters. The voltage applied to the base of t

reference signal from 3A2Q5 and 3A2Q6. The t r a n s i s t o r a c t s o n ly a s a p h ase - se n s i t i v

resultant dc output signal from this demodulator reference.

has a polarity corresponding to the original input

Fi gure 5-5. Synchronous demodul ator, sim pli f ied schemat ic diagr am.

5-9. Dr iver adjusted by 3A2R11. The frequency is factorThe driver, 3A2Q1 and 3A2Q2, is a two-transistor adjusted to 94 Hz.multivibrator circuit, the frequency of which is

Fi gur e 5-6. Dr iver, s impl i f i ed schemat i c d iagram.

5-



TM 11-6625-524-14-2

5-10. Reference Amplifier fo l lowers 3A2Q3 and 3A2Q4. The ampl i f ie rs

3A2Q5 and 3A2Q6 amplify this square wave, and

The 94-Hz squa re w a ve from the m odula tor dr iver it is coupled to the synchronous demodulator via

is sampled by the amplifier stages via emitter 3A2T1 .

Fi gure 5-7. Reference ampl if i er, sim pli f ied schemat ic di agram .

5-11. Dc Feedback and Calibration Controls of 3A2T2 and filter capacitor 3A1C6. For low

A port ion of the dc output voltage from the

synchronous demodulator is fed back to the dc

modulator to provide the excellent gain stability

of the voltmeter. This feedback rat io is deter-

mined by values of a resistor and potentiometer

connected in series and switched through section

H of range selector switch 3S2. One of the three

thermistors mounted in the rf probe is switched in

series with the previous combination by means of

sections C and E of 3S2. The dc feedback con-

trols, marked mid on the calibrat ion plate, are

used for accurate calibrat ion of the midscale for

each range. The appropriate feedback rat ion is

selected when switched to the desired range.

5-12. Output, Linearizing Networks, and Meter

CircuitThe dc output of the diodes in the probe is

basically nonlinear with respect to the rf input

l e v e l . I n o r d e r t o a c h i e v e a l i n e a r o u t p u t

characteristic, correction networks are employed.

Their function is to expand the lower end and

compress the upper end of the meter scale. Refer

t o figure 5-8 for be t t e r unders t and ing of the

circuit. The switch is at the 0.001 volt scale.

a. The rectified dc, proportional to the dc input

signal, appears at the center tap of the secondary

input levels, 50 percent of full scale and lower, the

s i g n a l p a s s e s t h r o u g h 3 A 3 R 2 2 , 3 A 3 R 2 1 ,

3A3CR6, 3M1, and 3A3R5. At low levels, the

re s i s t an c e o f 3 A 3 C R 6 i s f a i r l y h i g h an d t h ec u r r e n t t h r o u g h t h e c i r c u i t i s l i m i t e d . B y

paral le l ing 3A3R21 and 3A3CR6 with 3A3R17

and 3A3R25, an exact adjustment of the meter to

a point corresponding with the input voltage is

possible. For higher levels, 70 percent through

100 percent of full scale, 3A3R1, 3A3R35, and

3A3VR2 paralleled with 3M1 and 3A3R5 provide

adjustment of the meter to correspond with the

incoming signal. To adjust the midscale point,

the main dc feedback resistors are utilized.

b. Indicating meter 3M1 employes a taut band

movement t ha t is ra ted a t 0-500 microampere (ua)

d c . I t a l so u t i l i z e s a m i r ro r - b ac k e d sc a l e t o

minimize parallax errors.

c. Resis tor 3A3R5, in se r ies wi th 3M1, i s

connected to the circuit via 3J 2. For externa l

monitoring purposes, when a plug is inserted in

3J 2, 3A3R5 is sw itched out of the circuit a nd t he

external monitor must provide the 2K ohms series

load. This value should be within 1 percent to

maintain the rated cal ibrat ion accuracy of the

voltmeter.

5-6



Figure 5 10.

Figure 5 9.

5 13.

TM 11-6625-524-14

Figure 5-8. Scale corr ection network , schemat ic di agram .

base of 3A1Q1 is biased by the reference amplifie

via inverting-amplifier 3A1Q2. Transistor 3A1QThe electronically regulated power supply in- and its associated circuitry provide a constanelud es a 115/230 volt a c, 55 t o 65 H z du a l current of 1 milliampere (ma) to the referenc

pr imary , power t r ans former (3A1T1) . I t s amplifier and output stages. The regulatesecondary, in conjunction with rectifiers (3A1CR1 output voltage appears at the collector of 3A1Q1and 3A1CR2), is weed in a full-wave rectifying An adjustable voltage divider across the outpucircuit . The rect ifier output is applied to the consist ing of 3A1R12, 3A1R13, and 3A1R1emitter of series regulator transistor 3A1Q1. The permits a djustment of the output volta ge.

5



TM 11-6625-524-14

CHAPTER 6

G E N E R A L S U P P O R T M A I N T E N A N C E I N S T R U C T I O N S

Section I. TROUBLESHOOTING

6-1. Troubleshooting Techniques.

a. General . The first procedure in servicing a

defective voltmeter is to sectionalize the fault.

Sectionalization consists of tracing the fault to a

printed circuit b o a r d o r c h a s s i s . O n c e t h e

d e f e c t i v e b o a r d i s l o c a t e d , i s o l a t i o n t o t h e

defective part is accomplished. Troubleshooting

ia performed by the general support repairman.

b. Sect i onal i zat ion. Listed in (1) through (4)

below is a group of tests arranged to help locatethe defect.

(1) Visual inspection. When the voltmeter is

brought in for repair, remove the top cover and

inspect as follows:

(a) Check to see that all confections and pc

boards are properly seated. Repair or replace any

connections or leads that are broken or otherwise

defective.

(b) Check al l swi tches and controls fo

ease of operation.

(c) Inspect for loose or missing screw

(2) Operat iona l tests . O p e r a t i o n a l t e sfrequency indicate the general location of troubl

In many instances , the test will determine th

exact n a t u r e of t h e f a u l t . The opera t inprocedures (para 3-4), prevent ive maintenanc

checks (p a r a 4 -4 t o 4 -6 ) , a n d t h e a l i g n m e n

procedure (para 6-6) provide a good operationtest .

(3) Vol tage and resistance measurement

V o l t a g e a n d r e s i s t a n c e m e a s u r e m e n t a r

shown in figure 6-1. Several waveforms at cri t ic

poin ts a re shown in figure 5-10. Use these

localize trouble to a component.

6



TM 11-6625-524-14-2

Figure 6-1. Vo lt age and resist ance measurements.

(4) D C r es i s t a n c e o f t r a n s f o rm er s . D c dicat ions , o r l a c k o f m e t e r i n d i c a t i o n s a n dresistance of transformers are shown in paragraph operational checks provide a systematic method

6-6. of local izing trouble to the faul ty c i rcui t . The

(5) Tools and test equi pment . Tools and test trouble symptoms listed in the troubleshooting

equipment required for troubleshooting are shown chart (para 6-3) provide a dditional informa tion for

in section II. localizing troubles.

(6) Troub leshoo t i ng char t . The meter in-

6-2



TM 11-6625-524-14

Section II. TOOLS AND TEST EQUIPMENT

6-2. Tools and Test Equipment Required forTroubleshooting

a. Tools. No special tools are required.

Test equipment

E lectr onic Volt met er ME -30(*)/U

Oscilloscope AN/U SM -281

AC Meter, Millivac Model MV-45A

Signa l G enerat or AN/GR M-50

NOTE. (*) indicates all models.

6-3. Troubelshooting Chart

The fol lowing chart i s suppl ied as an a id in

locating trouble in the voltmeter. This chart lists

the symptoms observed during normal operation

Step Symptom

1

2

3

LINE lamp does not l ight when line

switch is turned to ON.

F u s e 3 A 3 F 1 b l o w s w h e n L I N E

switch is turned to ON,

LINE lamp l ights , vol tmeter does

not indicate on all ranges.

4 . Meter indicat ions abnormal on

r an g e s .

a ll

5 . Meter normal on all ranges but one.

6 Meter indication unstable or erratic.

6-4. Signal Tracing

b . T e s t E q u i p m e n t . T h e t e s t e q u i p m e

r e q u i r e d f o r t r o u b l es h o o t i n g i s l i s t e d b e l o w :

Technical manual Common name

TM 11-5511 Vtvm

TM 11-6625-1703-15 Scope

Ac meter

TM 11-6625-573-15 Signal Generator

t o l oc a l i ze th e t r ou b l e to a p c b oar d o r c omp on e

( I n c h a r t b e l ow , V & R s t a n d s f o r v o l t a g e a

r e s i s t a n c e .) U s e t h e p a r t s l o ca t i on i l l u s t r a t i o

( f i g s . 6- 2 t o 6 - 4 ) a n d s c h e m a t i c d i a g r a m (f i g . 5-

d u r i n g t r o u b l e s h o o t i n g .

Probable trouble

a. Fuse 3A3F1 is burned out.

b. LINE lamp 3DS1 defec t ive .

c. Defective power cord.

d. Line switch 3S1 defective.

e. 1 1 5 /2 3 0 v o l t s w i t c h 3 A 3 S 1

defective.

f. Transformer 3A1T1 defective.

Short circuit on power supply board.

a . Defec t on power supply board.

b, Defec t ive range se lec tor swi tch

3S2.

c. Defective met er 3 M 1

a. Defective modulator 3G1.

b. Defective amplifier board 3A2.

a. Check resistor on switch 3S2 for

defective range.

b. Check calibration resistors on 3A3board for defective range.

a. Defective cartridge in R F probe.

b. Power supply 3A1 defective.

c. Amplifier 3A2 defective.

Correction

a. Replace fuse. If new fuse blow

check steps 2 a nd 3 below.

b. Replace lamp.

c. C h e c k p o w e r c o r d ; r e p a i r o

replace.

d. C h e c k s w i t c h a n d r e p l a c e ,

necessary.

e. C h e c k s w i t c h a n d r e p l a c e ,

necessary.

f. Check transformer and replace,

necessary.Make V & R c h e c k s an d r e p l ac

faul ty par t .

a. Make V & R checks and repla

faul ty par t .

b. Check switch at defective range

Repair or replace.

c. Repair or r eplace.

a. Listen for a 94Hz hum. Replace

no hum.

b. Make V & R checks, Use sign

t r a c i n g ( p a r a 6 -4 ) . R e p l a

defective part.

a. Replace defective resistor.

b. Repla ce defective resistor.

a. R e m o v e a n d c h e c k c a r t r i d g

Replace if necessar y.

b. Repeat step 3 above.

c. Repeat step 4 above.

a n d p r e a m p l i f i e r c i r c u i t s . E x c e s s i v e

NOTE pickup will prevent making correct gain

When operat ing the vol tmeter removed and waveshape measurements. If pickup

f r o m t h e c a b i n e t , b e c a r e fu l t o a v o i d i s a p r ob le m , s h ie ld t h e v ol t m et e r b y

powerline hum pickup in the dc modulator placing aluminum plates at the bottom.

6



TM 11-6625-524-14-2

t op , an d s i d e s . S e t t h e p ow e r su p p l yvoltage at - 14.5 volts before making any

gain measurements.

a. Checking Waveshapes of 3A2 Am-

pl i f ier. Perform the following steps to check the

amplifier.

(1) Set the range selector switch at 0.001

range.(2) With no inpu t , ad jus t the SET REF

control until the meter pointer is at the SET REF

mark. The waveshape from 3A2TP5 to ground is

shown in figure 5-10.

(3) Connect the H-P 606A signal generator

to the rf probe.

(4) Set the signal generator output for 1 mv

at 200 KHz. The waveshape is shown in figure 5-

1 0 . A n y d ras t i c d e v i a t i on i n d i c a t e s a f au l t y

amplifier.

b . Check i ng Modu la to r and Na r row Band

Preamp l i f i e r . Perform the fol lowing steps to

check the modula tor and narrow band pream-plifier:

(1) Dis connect t he jumper bet w een 3A2TP 8and TP9.

(2) With no input, the waveshape at 3A2TP8is shown in figure 5-10.

(3) Connect the H-P 606A signal generator

to the rf probe.(4) Set the signal generator output for 1 mv

at 200 KHz. The waveshape is shown in figure 5-

10. I f the peak-to-peak output is low, adjust

3A2R11.

c. Checking Output Ampl i f ie r . P e r f o r m t h e

following steps to check the output amplifier.

(1)

connect

(2)connect

(3)

(4)

Disconnect the wire from 3A2TP12 and

it t o 3A2TP 11.

Disconnect the jumper from 3A2TP8 and

it t o 3A2TP 10.

Set the LINE switch at ON,

The volt a ge from 3A2TP 11 to groun d

sha ll measure 1.5 volts DC ± 10 percent . I f not ,

adjust 3A2R53.

6-5. Dc Resistance of Transformers

The dc resistance of transformers is shown below.

When using the data, observe the following:

a. Before making resistance measurements of

the windings, determine that the faulty operation

is due to a defect ive t ransformer. To do th is ,

f o l l o w t h e t r o u b l e s h o o t i n g p r o c e d u r e i n

paragraph 6-4.

b. B e c a u s e o f t h e r a t h e r b r o a d w i n d i n g

tolerances during manufacture, resistances may

vary from one transformer to another; the valuesshown are typical average values.

c. T h e n o r m a l r e s i s t a n c e of rep lacement

transformers may differ greatly from the values

given below.

Tr ansform er 3A1T1 Tr ansform ers 3A2T1 and T2

Termina ls Ohms Terminals Ohms

1-3 1.3

2-3 2-34-6

4-6

5-6

Section Ill. MAINTENANCE

6-6. Alignment

Perform the fol lowing steps to al ign the volt-

meter.

a. Connect the negative lead of the vtvm to

3A1TP 1 an d t he positiv e lead t o 3A1TP 2.

b. Adjust 3A1R13 (VOLTS ADJ U ST) for 14.5

volts indication on the vtvm.

c. With the power off, adjust the mechanical

zero adjust screw to bring th e meter pointer t o the

SET REF mark .

d. Terminate the rf probe in 50 ohms and

attach the probe to the voltmeter.

e. Set the LINE switch at ON.

f . Turn the SET REF control until the meter

pointer is at the SET REF mark.

6-7. Removal of Pc Board

Perform the following steps to remove a printed

circuit (pc) board.

a. Remove the six screws and washers located

at lower sides of the top cover and lift the cover up

b. clear the voltmeter.

b. Remove the five screws and washers on the

3A1 and 3A2 boards and lay the boards flat .

c. Unsolder and tag all wires connected to the

pc board and remove the board.

d. On the 3A3 pc board, perform the following

steps:

(1) Remove six screws and washers holdingthe rear plate .

(2) Remove six hexagon headscrews andwashers holding the board and lay the board f lat .

6-4



TM 11-6625-524-14

c. To replace the 3A3 board , per form t

following steps:

(1) Resolder all wires to the pc board a

components.

(2) Fasten the pc board to the chassis wi

six hexagon headscrews and washers removed

paragraph 6-7 d (2).

(3) Fasten the rear plate to the pc board wthe six screws and washers that were remov

(3) Unsolder and tag all wires connected to

the pc board and components and remove the

board .

6-8. Replacement of Pc Board

Perform the following steps to replace a pc board:

a. Resolder all wires to the 3A1 and 3A2 pc

boards .b. Fasten the pc board to the chassis with five

screws and washers removed in paragraph 6-7 b. (para 6- 7d (1).

Fi gure 6-2. Ampl if ier board 3A 2, location of part s.

6



Figure 6 3.

TM 11-6625-524-14-2

6 - 6



Figure 6 4.

TM 11-6625-524-14-2



Figure 7 1.

TM 11-6625-524-14

CHAPTER 7

G E N E R A L S U P P O R T T E S T I N G P R O C E D U R E S

7-1. G eneral Testing Procedures Ta ble 7-1. Test E quipm ent a. T estin g Pr ocedu res. The testing procedures

are prepared for use by Electronic Field Main-

t en a nce S h o p s a n d E le c t r on ic S er v i ce

Organizat ions responsible for general support

maintenance of electronic equipment to determine

the acceptabi l i ty of repaired equipment . These

procedures set forth specific requirements that

r e p a i r e d e q u i p m e n t m u s t m e e t b e fo r e i t i s

returned to the using organization.

b. Pre l im inary Inst ruct ions. Fol low the in-

s t r u c t i o n s p r e c e d i n g e a c h p r o c e d u r e b e f o r e

proceeding to the procedure. Perform each step in

sequence. Do not vary the sequence.

7-2. Test Equipment Required

Test equipm ent Techni cal manual

Oscilla tor AN/U RM-127 T. O. 33A1-8176Oscil loscope AN/U SM-281 TM 11-6625-170 3-15Varia ble Transform er C N-16B/UVoltmet er ME-30B/U TM 11-6625-320 -12Adapter . Milliva c So. 900-2100Cable Assembly. RF CG-409H

/U (2 ea )

7-3. P ower Supply Test

a. Test Equipment .(1) Os cilloscope AN/U S M-281.(2) Va ria ble Tra nsf ormer CN -16B/U .

The test equipment required for general support (3) Volt met er M E -30B /U .

testing is shown in table 7-1.

b. Test Connections. Connec t the uni t under

tes t (U U T) to th e CN-16B /U w hich is connected

to a 115-volt, 60-Hz source.

c. Procedure.

(1) Turn the range selector swi tch on the

UUT to the 3 VOLTS range.

(2 ) U s i n g t h e M E -3 0B /U , m e a s u r e t h e

volta ge a nd a djust th e CN-16B/U for a 115-volt

output .

(3) On the UUT, turn the LINE switch

ON.

(4) Connect th e ME -30B/U t o 3A1TP 1 a

3A1TP2 on the UUT (3A1TP2 is the negati

side).

(5) Adjus t 3A1R13 un t i l th e ME -30B/

reads 14.5-volt dc.

(6) Connect th e ME -30B/U from 3A1TP 2

c h a s s i s . A r e a d i n g o f - 8.6-volt ± 5 perce

should be obtained.

7



Figure 7 2.

TM 11-6625-524-14-2

(7) Con nect t he ME -30B/U from t he cent er

tap of the chopper driver coil (3G1) to the chassis.

A readin g of - 2.5-volt ± 20 percent sh ould be

indicated.

(8) Allow UUT to operate for 24 hours and

rech eck (5), (6), (7) a bove.

(9) C o n n e c t t h e A N /U S M -2 8 1 b e t w e e n

3A1TP1 and 3A1TP2 wi th vert ical gain a t 1

mil l ivol t /cent imet er (rev/cm). Ripple sh a l l be

from 0.5 to 1 microvolt (rev) at 120 Hz.

(10) Adjust C N - 16 B /U f o r 1 0 3 . 5 v o l t

output. There shall be no noticeable change in

ripple amplitude.

(11) Adju s t C N-16B /U for a 126 .5-vol t

output. No noticeable change in ripple amplitude

should occur.

7-4. Preamplifier and Amplifier Test

a. Test E qui pment .(1) Oscill oscope AN/U RM -281.

(2) Oscil la t or AN/U RM -127.

(3) Voltm et er M E -30B /U .

(4) Ada pt er, M illiva c No. 900-2100.

b. Test Connections.

(1) Conn ect t he AN/U RM-127 to t he d i-

vider.

(2) Conn ect th e ME -30B /U to mea sure t he

divider output voltage.

(3) Connect the adapter to the output of the

divider.

(4) Connect the UUT probe to the adapter.

c. Procedure.

(1) On t he AN/U RM-127, set th e outpu t to 0

db on the 10 volt ra nge at 60 Hz.

(2) Wi th the UUT out o f the case , usealuminum shields on the bottom and left side to

shield the unit from stray signals. Connect the

shields to the unit chassis.

(3) Conn ect th e ME-30B /U a t t he junct ion

of 3A2R6 and C7 and ground. The reading on the

ME-30B/U sha ll he great er th a n 60 db.

(4) Adjust the mechanical zero on the front

panel meter to SET REF.(5) Set the range selector switch at 0.001

range.

7-2

(6) Set the LINE switch at ON.

(7) C o n n e c t t h e A N /U S M -2 8 1 b e t w e e n

3A2TP 8 a nd ground.

(8) Adjus t t h e S E T R E F c o n t r o l f o r

minimum n o i s e o n t h e A N /U S M - 28 1 . Th e

reading shall be approximately 30 mvPP.

(9) On t he AN/U RM-127, set t he out put for

1 v ol t . Th e AN /U S M -2 81 s h a l l r e a d a p -

proximately 300 mvPP and the waveshape shall

be sinusoidal.

7-5. Voltage Accuracy Test

a. Test E qui pment .

(1) oscilla t or AN/U RM -127.(2) Voltm et er M E -30B /U .

(3) C a ble Assemb ly, R F C G -409H/U (4 FT)

(2 ea ch).

(4) BNC tee.

b. Test Connections.

(1) Connect the 50-ohm termination to the rf

probe and connect the probe to the UUT.

(2) Connect one end of th e CG -409H /U to

t he AN/U RM-127 out put .



TM 11-6625-524-14

(3 ) C o n n e c t t h e s e c o n d e n d o f t h e C G -

409H/U to one sid e of th e B NC Tee.

(4) Connect one end of the second CG -

409H/U to t he second sid e of the B NC Tee.

(5 ) C o n n e c t t h e s e c o n d e n d o f t h e C G -

409H/U t o th e ME -30B /U .

(6) Connect the r f probe to the BNC tee

output .c. Procedure. Adjus t t he AN/U RM -127

frequency to 500 KHz and the output amplitude

to the values shown below. The UUT readings

will be within tolerance.

UUT ME-30B/ U

range meter

selector indicat ion m in max

position (volt s )

.001 .003 .000285 .000315

.001 .006 .000570 .000630

.001 .001 .000950 .001050.003 .001 .000970 .001030

UUT

range meter

selector indicat ion

position (volts )

.003

.003

.01

.01

.01

.03

.03

.03

.1

.1

.1

.3

.3

.3

1

1

1

3

33

.002

.003

.003

.006

.01

01

.02

.03

.03

.06

.1

.1

.2

.3

.3

.6

1

1

23

ME-30B/ U

min max

.00194

.00291

.00291

.00582

.0097

.0097

.0194

.0291

.0291

.0582.

.097

.097

.194

.291

.291

.582

.97

.97

1.942.91

.00206

.00309

.00309

.00618

.0103

.0103

.0206

.0309

.0309

.0618

.103

.103

.206

.309

.309

.618

1.03

1.03

2.063.09

Fi gure 7-3. Voltage accur acy test setu p.

7



TM 11-6625-524-14-

APPENDIX AREFERENCES

The following is a l is t of re ferences that ar e avai lable to the operator , a nd organiza t ional and gener

support m a int ena nce personnel for t he AN/U RM-145B.

DA P a m 310-4 Index of Technical Manuals, Technical Bulletins, Supply Manuals (types

8, and 9), Supply Bullet ins, and Lubrication Orders.

DA P a m 310-7 Military Publicat ions: US Army Equipment Index of Modificat ion Wo

Orders.

TB 43-0118 Fie ld Ins t ruc t ions for Pa in t ing and Preserv ing E lec t ron ics Comman

Equipment Including Camouflage Pat tern Paint ing of Electrical Equi

ment Shelters.

TM 11-6625-320-12 Operator ’ s and Organ iza t ional Main tenance Manual : Vol tmeter , Met

ME -30A/U a nd Voltm eter s, E lectr onic ME-30B /U , ME -30C/U , a nd M

30E /U .

TM 11-6625-524-24P -2 Organizat ional , Direct Support , and General Support Maintenance Repa

Parts and Special Tools Lists (Including Depot Maintenance Repair Par

a nd S pecial Tools) for Voltm eter , El ectr onic AN/U RM-145B .

TM 11-6625-573-14-1 Operator’s, Organizational, Direct Support , and General Support Main

nance Manual Including Repair Parts and Special Tools Lists (IncludiDepot R epa ir P a rt s a nd S pecial Tools List): Genera tor, S ignal AN/G RM

50C.

TM 11-6625-683-15 Operator’s, Organizational, Direct Support , General Support , and Dep

Maint enance Ma nua l: Signa l G enerat or AN/U RM-127.

TM 11-6625-1703-15 Operator , Organizat ional , DS, GS, and Depot Maintenance Manual Inclu

ing R epair P a rt s a nd Special Tool List s: Os cilloscope AN/U SM-281A.

TM 38-750 The Army Maintenance Management System (TAMMS).

TM 740-90-1 Administrat ive Storage of Equipment.

TM 750-244-2 Procedure for Destruction of Electronics Materiel Equipment to Preve

Enemy Use (Electronics Command).

Change 1 A -

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TM 11-6625-524-14-2

APPENDIX C

MAINTENANCE ALLOCATION

Section I. INTRODUCTION

C-1. GeneralThis appendix provides a summary of the mainte-

na nce opera tions for AN/U RM-145B. I t a ut horizes

categories of maintenance for specif ic mainte-

nance functions on repairable items and compo-

nents and the tools and equipment required to

perform each function. This appendix may be used

as an aid in planning maintenance operat ions.

C-2. Maintenance Function

Maintenance functions will be limited to and de-

fined as follows:

a. I nspect. To determine the serviceability of anitem by compar ing its phys ical, mecha nical, a nd/or

electrical characterist ics with established stand-

ards through examinat ion .

b. Test. To verify serviceability and to detect in-

cipient failure by measuring the mechanical or

electrical characterist ics of an item and comparing

those characterist ics with prescribed standards.

c. Service. Operations required periodically to

keep an item in proper operating condition, i.e., to

clean (decontaminate), to preserve, to drain, to

paint , or to replenish fuel, lubricants, hydraulic

fluids, or compressed air supplies.

d. Adju st. To maintain, within prescribed limits,by bringing into proper or exact position, or by

s e t t i n g t h e o p e r a t i n g c h a r a c t e r i s t i c s t o t h e

specified parameters.

e. Al ign. To adjust specified variable elements of

an item to bring about optimum or desired perfor-

mance .

f . Cal i brate. To determine and cause corrections

to be made or to be adjusted on instruments or test

measuring and diagnostic equipments used in pre-

cision measurement. Consists of comparisons of

two instruments, one of which is a cert ified stand-

ard of known accuracy, to detect and adjust any

d iscrepancy in the accuracy o f the ins t rumentbeing compared.

g. I nstal l . The act of emplacing, seating, or fixing

into position an item, part, module (component or

assembly) in a manner to allow the proper func-

tioning of the equipment or system.

h. Repl ace. The act of substituting a serviceable

like type part, subassembly, or module (component

or assembly) for an unserviceable counterpart .

i . Repair . The applicat ion of maintenance serv-

ices (inspect , test , service, adjust , align, calibrate,

replace) or other maintenance actions (welding

g r i n d i n g , r i v e t i n g , s t r a i g h t e n i n g , f a c i n g , r e

m a c h i n i n g , o r r e s u r f a c i n g ) t o r e s t o r e s e r v

iceability to an item by correcting specific damage

fault , malfunction, or failure in a part , subassem

bly, module (component or assembly), end item, o

syst em. This function does not include the tr ial a n

error rep lacement o f runn ing spare t ype i t em

such as fuses, lamps, or electron tubes.

j . Over hau l . That maintenance ef fort (service

action) necessary to restore an item to a completel

serviceable/opera tiona l condit ion a s prescribed b

maintenance standards (i.e. , DMWR) in appropr

ate technical publicat ions. Overhaul is normallthe highest degree of maintenance performed b

the Army. Overhaul does not normally return a

item to like new condition.

k. Rebuild. Consist s of t hose services/a ct ion

necessary for the res tora t ion of unserv iceab l

equipment to a like new condit ion in accordanc

with orig inal manufacturing standards. Rebuild

t h e h i g h e s t d e g r e e o f m a t e r i e l m a i n t e n a n c

applied to Army equipment. The rebuild operatio

includes the act of returning to zero those ag

measurements (hours, miles, etc.) considered i

classify ing Army equipment s/components .

C-3. Column Entries

a. Column 1, Graup Number. Column 1 l is

group numbers, the purpose of which is to identi

components, assemblies, subassemblies, and mo

ules with the next higher assembly.

b. Colum n 2, Component / Assembly. Column

c o n t a i n s t h e n o u n n a m e s o f c o m p o n e n t s , a

semblies, subassemblies, and modules for whic

maintenance is authorized.

c. Colu mn 3, Main tenan ce Fu nctions. Column

lists the functions to be performed on the ite

listed in column 2. When items are listed withou

maintenance functions, it is solely for purpose

having the group numbers in the MAC and RPST

coincide.

d. Colum n 4, M ain tenan ce Categor y. Column

specifies, by the list ing of a “work t ime” figure

the appropriate subcolumn(s), the lowest level

maintenance authorized to perform the functi

listed in column 3. This figure represents the acti

t ime required to perform that maintenance fun

tion at the indicated category of maintenance.

the number or complexity of the tasks within t

Change 1 C-



l i s t ed main tenance funct ion vary a t d i f fe ren t

maintenance categories, appropriate, “work t ime”

f igures wil l be shown for each category. The

number of task-hours specified by the “work time”

figure represents the average t ime required to re-

store an item (assembly, subassembly, component,

module, end item or system) to a serviceable condi-

tion under typical field operating conditions. This

time includes preparation time, troubleshooting

time, a nd q uality assur an ce/qua lity control t ime in

addit ion to the t ime required to perform the spe-

cific tasks identified for the maintenance functions

authorized in the maintenance allocation chart .

Subcolumns of column 4 are as follows:

C - Opera tor /Cr ew

O - Organizational

F - Direct Support

H - G enera l Support

D - Depot

e. Colu mn 5, Tools and

specifies by code, those common tool sets (not indi-

vidual tools) and special tools, test, and supportequipment required to perform the designated

function.

f . C O lumn 6, Remar ks. Column 6 contains an al-

phabetic code which leads to the remark in section

IV, Remarks, which is pertinent to the item oppo-

site the part icular code.

C-4. Tool and Test Equipment Require-ments (Sect. III)

a. Tool or Test Equipment Reference Code. The

numbers in this column coincide with the numbers

used in the tools and equipment column of the

MAC. The numbers indicate the applicable tool or

test equipment for the maintenance functions.

b. Mai nt enan ce Category. The codes in this col-

umn indicate the maintenance category allocatedthe tool or test equipment.

c. Nomenclat ur e. This column lists the noun

name and nomencla ture o f the tools and t es t

equipment required to perform the maintenance

functions.

d. Nat ional / NAT O Stock N umber. This column

list s th e Nat iona l/NATO st ock num ber of the spe-

cific tool or test equipment.

e. Tool Number. This column lists the manufac-

turer’s part number of the tool followed by theFederal Supply Code for manufacturers (5-digit) in

parentheses.

C-5. Remarks (Sect. IV)

a. Refer ence Code. This code refers to the appro-

priate item in section II, column 6.

b. Remaks. This column provides the required

explanatory information necessary to clarify items

appearing in section II .

C-2 Change 1



TM 11-6625-524-14-

SECTION IV. REMARKS

REFERENCE

CODEREMARKS

A External Receptacles, meter glass, knobs, controls, and switches for proper action,cables for cuts, cracks or fraying external hardware, rust and corrosion.

B Clean exterior surfaces, remove dirt, grease end fungus, rust and corrosion. Apply touchuppaint.

C Repair through replacement of burned out fuse, defective knobs and switches.

D Loose or missing hardware check switches, controls, connections and PC boards.

E Replace missing or defective hardware.

F Operational checks to localize troubles. Voltage & resistance measurements, voltage accuracytests.

G Voltage adjustments.

H Voltage and ripple tests.

I Output voltage adjustments.

J Noise, Voltage and Waveshape Tests.

Change 1



TM 11-6625-524-1

F i gu re 5 -9 . Regu l a ted powe r supp l y , simp l i f i e d schema t i c d i ag ra m



TM 11-6625-524-14-2

By Order of the Secretary of the Army:

Official:

VERNE L. BOWERS

Major General , Uni ted St ates Army,Th e Adj utant General .

Distr ibut ion:

F R E D C . WE Y A N D

Genem l, U ni ted States ArmyVi ce Chi ef of Staff .

To be distributed in accordance with DA Form 12-36, Direct and General

Su pport m a int ena nce requ iremen ts f or AN/ARC-102 a nd AN/TSQ -72. a nd D A

Form 12-51 Direct a nd G enera l Support ma intena nce requirement s for AN/G RC-

106, AN/G RC -108 a n d AN /TRC -90.



THE METRIC SYSTEM AND EQUIVALENTS

tm 11-6625-524-14-2_voltmeter_an_urm-145_1974

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