HP 400D, 4001, 400H, H02-400D Organizational, Ds, Gs, And Depot Maintenance Manual

TM 11-6625-1514-15

DEPARTMENT OF THE ARMY TECHNICAL MANUAL

ORGANIZATIONAL, DS, GS,

AND DEPOT MAINTENANCE MANUAL

HEWLETT-PACKARD

VOLTMETER

400D, 400H, 4001

This copy is a reprint which includes current
pages from Changes 1.

VACUUM TUBE

MODELS

AND H02-400D

HEADQUARTERS, DEPARTMENT OF THE ARMY

MAY 1967

WARNING

DANGEROUS VOLTAGES

EXIST IN THIS EQUIPMENT

Be careful when working on the power supplies and

their circuits, or on the 230 or 115-volt ac line

connections.

DO NOT TAKE CHANCES

TM 11-5625-1514-15

C1

C

HANGE

HEADQUARTERS

DEPARTMENT OF THE ARMY

No. 1

Washington DC, 28 September 1982

Organizational, Direct Support, General Support and

Depot Maintenance Manual

HEWLETT–PACKARD VACUUM TUBE VOLTMETER MODELS

400D, 400H, 400L, and H02-400D

(NSN 6625-00-643-1670)

TM 11-6625-1514-15, 23 May 1967, is changed as follows:

1. Title of manual is changed as shown above.

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

3. Added or revised illustrations are indicated by a vertical bar next to the figure caption.

4. Remove old pages and insert new pages as indicated below:

Remove pages

None. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

i and 1-0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i, ii and 1-0

1-0.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-0.1

10-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5

5. File this change sheet in front of the publication for reference purposes.

. Warning page a/(b blank)

Insert pages

By Order of the Secretary of the Army:

Official:

ROBERT M. JOYCE

Major General, United States Army

The Adjutant General

Distribution:

To redistributed in accordance with special list.

E. C. MEYER

General, United States Army

Chief of Staff

TM 11-6625-1514-15

SAFETY STEPS
IS THE VICTIM

TO FOLLOW IF
OF ELECTRICAL

SOMEONE

SHOCK

DO NOT TRY TO PULL OR GRAB THE INDIVIDUAL

IF POSSIBLE , TURN OFF THE ELECTRICAL POWER

IF YOU CANNOT TURN OFF THE ELECTRICAL
POWER, PULL, PUSH, OR LIFT THE PERSON TO

SAFETY USING A WOODEN POLE OR A ROPE OR

SOME OTHER INSULATING MATERIAL

SEND FOR HELP AS SOON AS POSSIBLE

AFTER THE INJURED PERSON IS FREE OF

CONTACT WITH THE SOURCE OF ELECTRICAL
SHOCK, MOVE THE PERSON A SHORT DISTANCE
AWAY AND IMMEDIATELY START ARTIFICIAL

RESUSCITATION

Change 1 a/(b blank)

This manual contains copyright material reproduced by permission of the Hewlett-Packard Company.

TM 11-6625-1514-15

Technical Manual

HEADQUARTERS

DEPARTMENT OF THE ARMY

No. 11-6625-1514-15

Washington, DC, 23 May 1967

ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND

DEPOT MAINTENANCE MANUAL

HEWLETT-PACKARD VACUUM TUBE VOLTMETER MODELS

400D, 400H, 400L, AND H02-400D

(NSN 6625-00-643-1670)

Paragraph

Section

Section

Section

Section

Section

I.

GENERAL DESCRIPTION

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Index of Technical Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Maintenance Forms, Records, and Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reporting Errors and Recommending Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reporting Equipment Improvement Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Administrative Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Destruction of Army Electronics Materiel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

II.

INSTALLATION

Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Line Voltage Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Line Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Operation Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

III.

OPERATING INSTRUCTIONS

Instrument Turn-On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General Operating Information.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Low-Level Measurements and Ground Currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measurement of Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Measurement of Decibels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Impedance Correction Graph . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Use of Voltmeter Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IV.

CIRCUIT DESCRIPTION

Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Input Voltage Divider and Step Attenuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Broadband Voltmeter Amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Indicating Meter Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

V.

MAINTENANCE

Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Precautions . . . . . . . . . . . . . . . . . . . . . . . .

Test Equipment Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Meter Zero Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Cabinet Removal . . . . . . . . . . . .

Tube Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Replacement of Special Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Trouble Shooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Testing the Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Testing Voltmeter Performance

Calibration and Frequency Response Adjustments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

1-A.1
1-A.2
1-A.3
1-A.4
1-A.5
1-A.6
1-A.7

1-1
1-4

2-1
2-3
2-5
2-8

2-10

3-1

3-3

3-12

3-14
3-17
3-20
3-22

4-1
4-3
4-7

4-10
4-14

5-1
5-3
5-5
5-7
5-9

5-10
5-13
5-17
5-20
5-22
5-24

Page

1-0.1
1-0.1
1-0.1
1-0.1
1-0.1
1-0.1
1-0.1
1-1
1-1

2-1
2-1
2-1
2-1
2-1

3-1
3-1
3-2
3-2
3-3
3-3
3-4

4-1
4-1
4-1
4-1
4-2

5-1
5-1
5-1
5-1
5-2
5-2
5-2
5-3
5-3
5-5
5-8

Change 1 i

TM 11-6625-1514-15

Section

Section

Section

Section
Section

ILLUSTRATED PARTS BREAKDOWN

VI.

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GROUP ASSEMBLY PARTS BREAKDOWN

VII.

Vacuum Tube Voltmeter 400D/H/L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Main Chassis Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Range Switch Assembly 400D-19A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Printed Circuit Board Assembly 400D-75G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Printed Circuit Board Assembly 400D-75F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Printed Circuit Board Assembly 400D-65C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

VIII.

NUMERICAL INDEXES

Part No. Numerical Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Hewlett-Packard Stock No. Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

REFERENCE DESIGNATION INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

IX.

AUXILIARY EQUIPMENT

X.

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Line Matching Transformer Model 11004A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Bridging Transformer Model 11005A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Final Performance Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Paragraph

6-1
7-1

7-2
7-3
7-4
7-5
7-6

10-1
10-3
10-7
10-8

Page

6-1
7-1

7-3

7-8
7-9
7-10
7-12

8-1
8-2
9-1

10-1
10-1
10-5
10-5

ii

Change 1

1-0

Change 1

TM 11-6625-1514-15

Figure 1-1.

SECTION I

GENERAL DESCRIPTION

TM 11-6625-1514-15

1-A.1. Scope

This manual includes installation and operation in­structions and covers operator’s, organizational,
direct support (DS), general support (GS), and depot
maintenance. It describes Hewlett-Packard (Federal
Supply Code 28480) Vacuum Tube Voltmeter Models
400D and H02-400D, serial numbers 310-45571 and
higher; and Models 400H and 400L, serial numbers
313-22177 and higher. A basic issue items list for this
equipment is not included in this manual.

1-A.2. Index of Technical

Publications

Refer to the latest issue of DA Pam 310-4 to deter­mine whether there are new editions, changes or ad­ditional publications pertaining to the equipment.

1-A.3. Maintenance Forms, Records,

and Reports

a. Reports of Maintenance and Unsatisfactory

Equipment.

cedures used for equipment maintenance will be
those prescribed by TM 38-750, The Army
Maintenance Management System (Army). Air Force
personnel will use AFR 66-1 for maintenance repor­ting and TO-00-35D54 for unsatisfactory equipment
reporting.

b. Report of Packaging and Handling Deficien-

cies. Fill out and forward SF 364 (Report of

Discrepancy (ROD)) as prescribed in AR 735-11-2/
DLAR 4140.55/NAVMATINST 4355.73/AFR 400­54/MCO 4430.3E.

c. Discrepancy in Shipment Report (DISREP)

(SF 361).

ment Report (DISREP) (SF 361) as prescribed in AR
55-38/NAVSUPINST 4610.33B/AFR 75-18/MCO
P4610.19C/DLAR 4500.15.

Department of the Army forms and pro-

Fill out and forward Discrepancy in Ship-

1-A.4. Reporting Errors and Recom-

mending Improvements

You can help improve this manual. If you find any

mistakes or if you know of a way to improve the pro­cedures, please let us know. Mail your letter or DA
Form 2028 (Recommended Changes to Publications
and Blank Forms) direct to Commander, US Army
Communications-Electronics Command and Fort
Monmouth, ATTN: DRSEL-ME-MQ, Fort Mon­mouth, NJ 07703. A reply will be furnished direct to
you.

1-A.5. Report Equipment Improve-

ment Recommendations (EIR)

If your vacuum tube voltmeter needs improvement,
let us know. Send us an EIR. You, the user, are the
only one who can tell us what you don’t like about
your equipment. Let us know why you don’t like the
design. Tell us why a procedure is hard to perform.
Put it on an SF 368 (Quality Deficiency Report).
Mail it to Commander, US Army Communications­Electronics Command and Fort Monmouth, ATTN:
DRSEL-ME-MQ, Fort Monmouth, NJ 07703. We’ll
send you a reply.

1-A.6. Administrative Storage

Administrative storage of equipment issued to and
used by Army activities will have preventive
maintenance performed before storing. When
removing
storage, the PMCS should be performed to assure
operational readiness.

1-A.7. Destruction of Army Elec-

Destruction of Army electronics materiel to prevent

enemy use shall be in accordance with TM 750­244-2.

the equipment from administrative

tronics Materiel

Change 1

1-0.1

TM 11-6625-1514-15

Paragraphs 1-1 to 1-5

Section I

1-1. INTRODUCTION.

1-2. This manual contains operating and servicing
instructions, and a parts breakdown, for the Models
400D, 400H, and 400L Vacuum Tube Voltmeters manu­factured by the Hewlett- Packard Company. The Model
400D Voltmeter is similar to a military counterpart,
Electronic Voltmeter ME-30A/U, in appearance and
operation, but contains modified electrical circuits
to obtain improved performance. Applicable Federal
Stock Numbers for the voltmeters are as follows:

Model 400D: 6625-643-1670
Model 400H: 6625-557-8261
Model 400L: 6625-729-8360

1-3. The Models 400D, 400H, and 400L Voltmeters
are the same except for the differences listed in Fig­ure 1-2.

a. Voltage Range: 400D/H - 0.1 millivolt to 300
volts; 400L - 0.3 millivolt to 300 volts, in 12 ranges
providing full-scale readings of the following voltages:

0.001

0.003 0.300 30.00

0.010

0.030 3.000

b. Decibel Range: -72 to +52 db, in 12 ranges.
c. Frequency Range: 10 cps to 4 mc.

d. Input Impedance: 10 megohms shunted by 15 pf

(15 µµf) on ranges 1.0 volt to 300 volts; 25 pf on ranges

0.001 volt to 0.3 volt.

e. Stability: Line voltage variations of ±10% do not
reduce the specified accuracy, and line voltage transients
are not reflected in the meter reading. Electron tube
deterioration to 75% of normal transconductance affects
accuracy less than 0.5% from 20 cps to 1 mc.

f. Amplifier: OUTPUT terminals are provided so
that the voltmeter can be used to amplify small signals
or to enable monitoring of waveforms under test with
an oscilloscope. Output voltage is approximately 0.15

volt rms on all ranges with full-scale meter deflection.
Amplifier frequency response is same as the voltmeter.
Internal impedance is approximately 50 ohms over
entire frequency range.

(See figure l-l. )

0.100

1.000

10.00

100.00

300.00

a. The front panel meters are different in each

model, as described in paragraph 1-6.

b. The accuracy specifications are different for

each model, as described in figure 1-2.

1-4. DESCRIPTION.

1-5. The Hewlett-Packard Models 400D, 400H, and
400L Vacuum Tube Voltmeters are general purpose,
portable electronic a-c voltmeters of high sensitivity
and stability. They are suited to both laboratory and.
field use. Models 400 D/H measure a-c voltages from

0.001 to 300 volts and Model 400L from .003 to 300
volts rms full scale, with a frequency bandwidth cover­ing 10 cps to 4 megacycles. The voltmeters are com­pact, accurate, and rugged and have fast meter re­sponse, high input impedance, stable calibration ac­curacy, and freedom from the effects of normal line

—

voltage variations.

long instrument life with a minimum of servicing.

g. Accuracy: Model 400D -

± 2% of full scale, 20 cps to 1 mc;
± 3% of full scale, 20 cps to 2 mc;
± 5% of full scale, 10 cps to 4 mc.

Model 400H -

± 1% of full scale, 50 cps to 500 kc;
± 2% of full scale, 20 cps to
± 3% of full scale, 20 cps to

+ 5% of full scale, 10 cps to

Model 400L -

±2% of reading or ±1% of full scale,

whichever is more accurate,
50 cps to 500 kc.

±3% of reading or ±2% of full scale,

whichever is more accurate,
20 cps to 1 mc.

±4% of reading or ±3% of full scale,

whichever is more accurate,

20 cps to 2 mc.

±5% of reading 10 cps to 4 mc.

h. Power Requirement:

1000 cps, approximately 100 watts.

i. Size: 11-3/4 in. high, 7-1/2 in. wide, 12 in. deep.
j. Weight: 18 lbs; shipping weight approximately

23 lbs.

The voltmeters are designed for

1 mc;
2 mc;
4 mc.

115/230 volts ±10%, 50 to

00102-3

Figure 1-2. Table of Specifications

1-1

TM 11-6625-1514-15

Section I

Paragraphs 1-6 to 1-10

1-6. Each model voltmeter has three calibrated scales
on the panel meter.
two linear VOLTS scales, 0 to 1 and 0 to 3, and one
DECIBELS scale,
the Models 400H and 400L are larger and include a
mirror to eliminate parallax in viewing and to facilitate
use of the higher scale calibration accuracy of these
models. The Model 400L VOLTS scales are logarithmic
in calibration, from 0.3 to 1 and 0.8 to 3; and the
DECIBELS scale is linear. In all models, the VOLTS
scales are calibrated to indicate the root-mean-square
(rms) value of an applied sine wave. Actual meter
deflection is proportional to the average value of the
applied signal, thereby minimizing additional meter
deflection due to noise and harmonic distortion.

1-7. A voltmeter output signal is provided at the front
panel OUTPUT terminals.
to the meter reading and has a waveshape similar to the
applied signal.

rms for a full-scale meter reading, regardless of the
input signal level. The internal impedance at the
OUTPUT terminal is 50 ohms over the full frequency
range.
adversely affect the accuracy of the voltmeter. This
output is valuable for increasing the sensitivity of
bridges, etc., where distortion added to the waveform

is not a factor.

1-8. The voltmeter chassis is constructed of aluminum
alloy throughout. The panel is finished in non-reflecting,
light-grey baked enamel; the cabinet is finished in
dark-blue, baked wrinkle paint. The cabinet is equipped
with rubber feet and a leather carrying handle. Control
markings on the front panel are engraved and black
filled. INPUT and OUTPUT terminals are special
binding posts which accept either bare wire or banana
plugs; the 3/4-inch spacing between binding posts accepts
standard dual-banana plugs. The “ground” side of the
INPUT and OUTPUT terminals is connected to the
instrument chassis which is in turn connected to the

power line ground through the third (round) prong of
the plug on the power cable.

High-impedance loads (above 100K) will not

The Models 400D and 400H have

-12 to +2 db. The meters used in

This output is proportional

This signal level is about 0.15 volts

1-9. The voltmeter is equipped with a non-detachable
power cord. Test leads, which may be plain wire leads
or coaxial cable, and test probes must be supplied by
the user.

1-10. Instruments designated Models 400DR, 400HR,

and 400LR are rack mount configurations of the 400D,

400H, and 400L, respectively. They are identical to
their cabinet model counterparts in every other re-

spect. They are designed to be mounted in a stan­dard 19 inch wide x 7 inch high relay rack space. Re­fer to Appendix C for Replacement Parts information.

1-2

2-1. UNPACKING AND INSPECTION.

TM 11-6625-1514-15

Section II

Paragraphs 2-1 to 2-11

SECTION II

INSTALLATION

2-2. There are no special precautions for unpacking
the voltmeter. Save the shipping carton and packing
materials for possible storage or reshipment. When
unpacking, inspect instrument and packing materials
for signs of damage in shipment. Make an operation
check as directed in paragraph 2-10 to determine if
performance is satisfactory. If there is any indication
of damage or deficiency, refer to

paragraph 1-A.3.

2-3. LINE VOLTAGE REQUIREMENT.

2-4. The voltmeter is wired at the factory for use on

115-volt a-c power. This voltage may vary ±10% without
adverse effect upon voltmeter performance. The volt­meter can be wired for use on 230-volt a-c power by
reconnecting the dual primary windings on the power
transformer as shown in the schematic diagram in
Section V. When using 230-volt power, change from
a 1-amp to a 1/2-amp slow-blow fuse. If necessary,
provide an adapter for attaching the standard 115-volt
plug on the voltmeter to the 230-volt outlet.

2-5. POWER LINE CONNECTION.

2-6. The three-conductor power cable on the voltmeter

is terminated in a polarized three-prong male connector.
The third contact is an offset round pin added to a stand­ard two-blade connector, which grounds the instrument
chassis when used with the appropriate receptacle.
To connect this plug in a standard two-contact receptacle,

use an adapter. The chassis ground connection is

brought out of the adapter in a green pigtail lead for

connection to a suitable ground.

The lower INPUT and OUTPUT signal terminals
on the panel of the voltmeter are connected
directly to the chassis of the voltmeter. Any
voltage applied to the lower terminal will be
shorted directly to ground. If the ground con­nection in the power cord is disconnected by
use of an adapter, the entire voltmeter cabinet
will carry whatever potential is applied to the

lower terminal and may be a hazard to the
operator.

2-8. INSTALLATION.

2-9. The voltmeter is a portable instrument requiring
no permanent installation. The voltmeter is for bench­top operation, standing on its rubber feet with its front

panel near the vertical plane. A bail is provided for

raising the front of the cabinet to obtain a better viewing

angle.

2-10. OPERATION CHECK.

2-11. The voltmeter is ready for use as received from
the factory. The simple check described below can be
made by incoming inspectors to determine if electrical

damage was incurred in shipment. If more complete

proof of instrument performance is required, the over-all
performance check described in paragraph 5-22 must be
used. Make a simple performance check as follows:

a. Connect voltmeter to the power line through a
variable transformer. Set transformer for 115 volts,
turn on and allow a five-minute warmup.

2-7. The power plug normally supplied with the volt-

meter is made of molded rubber and is an integral
part of the power cable. On certain military contracts,
a modification of the Model 400D, termed the H02-400D,

is equipped with a removable plug having the same pin
configuration but constructed of corrosion-resistant

material. In all other respects the H02-400D is the

same as the Model 400D and carries the same Federal
Stock Number.

00102-2

b. Measure any sine wave voltage, excepting the power

line,

from 0.01 to 300 volts whose exact voltage is known.
Note that the lower INPUT terminal is connected to the
power line ground.

c. While making the above measurement, adjust the
line voltage from 103 to 127 volts. The reading on the
meter must not change by more than the width of the
pointer.

2-1

TM 11-6625-1514-15

Section III

3-0

Figure 3-1. Voltmeter Front Panel, Showing Controls and Connectors

00102-2

SECTION III

OPERATING INSTRUCTIONS

TM 11-6625-1514-15

Section III

Paragraphs 3-1 to 3-9

3-1. INSTRUMENT TURN-ON.

3-2. The voltmeter is ready for use as received from
the factory and will give specified performance after a
few minutes warmup. See Section II for information
regarding connection to the power source and to the
voltage to be measured. Controls are shown in figure 3-1.

3-3. GENERAL OPERATING INFORMATION.

3-4. METER ZERO CHARACTERISTIC. When the
Model 400D and 400H Voltmeters are turned off, the

meter pointer should rest exactly on the zero calibration
mark on the meter scale. If it does not, zero-set the
meter as instructed in paragraph 5-7. The meter

supplied in the Model 400L Voltmeter is not provided
with a mechanical meter zero adjustment. When the
voltmeter is turned on with the INPUT terminals

shorted, the meter pointer may deflect upscale slightly;

this deflection does not affect the accuracy of a reading.

NOTE

When the voltmeter RANGE switch is set to the
lowest ranges and the INPUT terminals are not
terminated or shielded, noise pickup can be
enough to produce up to full-scale meter deflec­tion. This condition is normal and is caused
by stray voltages in the vicinity of the instru­ment. For maximum accuracy on the .001-volt
range, the voltage under measurement should
be applied to the voltmeter through a shielded
test lead.

3-5. METER SCALES. The two voltage scales on each

of the voltmeter models are related to each other by
a factor of 1 10 (10 db). In conjunction with the calib-

rated RANGE switch steps, this provides an intermediate

range step spaced 10 db between “power of ten” ranges,
which are 20 db apart. The relationship of the DECIBELS
scale to the 0 to 1 VOLT scale is determined by making
0 db on the DECIBELS scale equal to the voltage required
to produce 1 milliwatt in 600 ohms (0.775 volts). Thus,

the DECIBELS scale reads directly in dbm (decibels

referred to one milliwatt) across a 600-ohm circuit,
and can be used to measure absolute level of sine wave
signals. It can also be used to measure relative levels
of any group of signals which have the same waveform,

across any constant circuit impedance. The RANGE

switch changes voltmeter sensitivity in 10-db steps

accurate to within ± 1/8 db. The RANGE switch position

indicates the value of a full-scale meter reading.

3-6. CONNECTIONS. Voltmeter test leads must be
provided by the user. The type of leads and probes
used will depend upon the application, as listed below:

a For connection to low-impedance signal sources,

plain wire leads often are sufficient.
00102-2

b. For high-impedance sources, or where noise pickup

is a problem, low-capacity shielded wire must be used
with a shielded, dual banana plug for connection to the
voltmeter terminals.

c. If a probe is used, it should also be shielded to

prevent pickup from the hand.

d. For signals above a few hundred kilocycles, the
capacity of the test leads must be kept to a minimum
by using very short leads, preferably unshielded. An
alligator clip should be used at the test end so that
connection can be made without adding the capacity of
the user’s hands.

3-7. MAXIMUM INPUT VOLTAGE. Do not apply more
than 600 volts de to the INPUT terminals. To do so ex­ceeds the voltage rating of the input capacitor.

3-8. If an applied voltage momentarily exceeds the
selected full-scale voltmeter sensitivity, a few seconds
may be required for circuit recovery, but no damage

will result.
3-9. INPUT VOLTAGE WAVEFORM. The voltmeter

is calibrated to indicate the root-mean-square value
of a sine wave; however, meter pointer deflection is
proportional to the average value of whatever waveform
is applied to the input.

is not a sine wave, the reading will be in error by an
amount dependent upon the amount and phase of the
harmonics present, as shown in figure 3-2 below.
When harmonic distortion is less than about 10%, the
error which results is negligible.

INPUT VOLTAGE

CHARACTERISTICS

Fundamental = 100
Fundamental +10%

2nd harmonic

Fundamental +20%

2nd harmonic

Fundamental +50%

2nd harmonic

Fundamental +10%

3rd harmonic

Fundamental +20%

3rd harmonic

Fundamental +50%

3rd harmonic
Note: This chart is universal in application since
these errors are inherent in all average-respond­ing type voltage-measuring instruments.

Figure 3-2. Effect of Harmonics on Voltage

Measurements

If the input signal waveform

TRUE

RMS

VALUE

100

100.5
102
112

100.5
102
112

METER

INDICATION

100

100
100-102
100-110

96-104
94-108
90-116

3-1

TM 11-6625-1514-15

Section III

Paragraphs 3-10 to 3-16

Figure 3-3. Test Setup for Avoiding Ground Loop

3-10. Since the voltmeter meter deflection is propor-

tional to the average value of the input waveform, it

is not adversely affected by moderate levels of random

noise. The effect that noise has on the accuracy of the
meter reading depends upon the waveform of the noise
and upon the signal-to-noise ratio. A square wave has
the greatest effect, a sine wave intermediate effect, and

“White” noise has the least effect on the meter reading.
3-11. If the noise signal is a 50% duty cycle square wave

and the signal-to-noise ratio is 10:1 (between peak
voltages), the error will be about 1% of the meter

reading. If the noise signal is “white” noise and the
signal-to-noise ratio 10:1, the error is negligible.

3-12. LOW-LEVEL MEASUREMENTS AND GROUND
CURRENTS.

3-13. When the voltmeter is used to measure signal
levels below a few millivolts, ground currents in the
meter test leads can cause an error in meter reading.
Such currents are created when two or more ground
connections are made between the instruments of a
test setup and/or between the instruments and the power

line ground. Two ground connections complete an
electrical circuit (ground loop) for the voltages which
are generated across all instrument chassis by stray
fields, particularly the fields of transformers. These
ground currents can be minimized by disconnecting
the ground lead in the power cord from either the
voltmeter or the signal source being measured, at the
power outlet as shown in figure 3-3, and by making

sure that in the test setup no other ground loop is
formed that can cause a ground current to flow in the
voltmeter test leads. Although the resultant voltage
developed across a test lead is in the order of micro­volt, it is enough to cause noticeable errors in
measurements of a few millivolts. The presence of

ground currents can sometimes be determined by

simply changing the grounds for the instruments in the

3-2

setup and watching for a change in meter reading. If
changing the ground system causes a change in meter

reading, ground currents are present.

3-14. MEASUREMENT OF VOLTAGE.

3-15. The meter has two VOLTS scales, 0 to 1 and
0 to 3. When the RANGE switch is set to .001, .01,

.1, 1, 10, or 100 VOLTS, read the 0 to 1 scale. When
the RANGE switch is set to .003, .03, .3, 3, 30, or 300
VOLTS, read the 0 to 3 scale.

The lower (black) signal INPUT and OUT­PUT terminals and the instrument case are
connected to the power system ground when
the instrument is used with a standard three­terminal (grounding) receptacle. Connect
only ground-potential circuits to the black
INPUT and OUTPUT terminals.

3-16. Operate the instrument as follows:

a. Connect the voltmeter to the a-c power source.
b. Turn the Power switch ON and allow a warmup

period of approximately five minutes.

c. Disconnect any external equipment from the OUT-

PUT terminals.

d. Set the RANGE switch to the VOLTS range which
will read the voltage to be measured at mid-scale or
above. If in doubt, select a higher VOLTS range.

e. Connect the voltage to be measured to the INPUT
terminals.

00102-2

AVOID A SHORT CIRCUIT ACROSS THE POW­ER LINE! To measure power line voltage, first

connect only the upper (red) INPUT terminal to

each side of the power line, in turn, leaving it
connected to the side that causes meter indi­cation. Then connect the lower (black) INPUT

terminal (grounded internally) to the other side
of the line. If this procedure is not followed,
the power line may be short-circuited through
the grounded INPUT terminal of the voltmeter.

TM 11-6625-1514-15

Section III

Paragraphs 3-17 to 3-21

f. Note the meter indication on the DECIBELS scale

(-12 to +2 db). The signal level is the algebraic sum of
the meter indication and the db value indicated by the
RANGE selector. Study the following examples:

Example 1
If the indication on the DECIBELS scale is +2 and the

RANGE switch is in the +20 DB position, the level is
+22 dbm.

Example 2
If the indication on the DECIBELS scale is +1.5 and the
RANGE switch is in the -40 DB position, the level is

-38.5 dbm.

f. Read the meter indication on the appropriate VOLTS

scale, in accordance with the full-scale value indicated
on the RANGE switch. Evaluate the reading in terms
of the full-scale value indicated on the RANGE switch.
Study the following examples:

Example 1

When the RANGE switch is in the .1 VOLTS range, read

the 0 to 1 VOLTS scaIe. If the meter indicates .64 on

that scale, the voltage being measured is:

Example 2
When the WGE switch is in the 30 VOLTS range, read

the 0 to 3 VOLTS scale. If the meter indicates 1.6 on

that scale, the voltage being measured is:

3-17. MEASUREMENT OF DECIBELS.

3-18. The DECIBELS meter scale is provided for
measuring dbm directly across 600 ohms and for
measuring db ratio for comparison purposes when
each measurement is made across the same circuit

impedance. To measure signal level directly in dbm

(0 dbm equals 1 milliwatt into 600 ohms) proceed as
follows:

a. Connect the voltmeter to the a-c power source.
b. Turn the Power switch ON and allow a warmup

period of approximately five minutes.

c. Disconnect any external equipment from the OUT-

PUT terminals.

d. Set the RANGE switch to the DB range which will
give an upscale reading of the signal to be measured.
If in doubt, select a higher-level scale.

e. Connect the voltage to be measured to the INPUT
terminals.

00102-2

3-19. To measure db across impedances other than
600 ohms, follow the above procedure and evaluate the

results as follows:

NOTE

Since the measurement is made across other
than 600 ohms, the level obtained in step f is in
db, but not in dbm.

a. To obtain the difference in db between measure­ments made across equal impedances, algebraically
subtract the levels being compared.

b. To obtain the reading of a single measurement

in dbm, note the impedance across which the measure­ment is made and refer to the Impedance Correction
Graph, described in paragraph 3-20.

c. To obtain the difference in dbm between measure-

ments made across different impedances, convert each
measurement to dbm using the Impedance Correction
Graph described in paragraph 3-20. Then algebraically
subtract the dbm levels being compared.

3-20. IMPEDANCE CORRECTION GRAPH.

3-21. As the voltmeter DECIBELS scale is calibrated
to indicate dbm for measurements made across 600-ohm
circuits, a correction factor must be used when meas­urements are made across circuit impedances other
than 600. ohms, if absolute dbm levels are desired. The
correction factor is not necessary in measuring relative
db levels (not dbm) across the same impedance, but it is
required for comparison of db levels measured across
different impedances.

in figure 3-4 gives the correction factor for conversion
of the meter reading to dbm when the impedance of
the circuit under test is known. To use the graph, read
the conversion factor corresponding to the test circuit
impedance and add it to the meter reading determined
by the method of paragraph 3-17. Observe the algebraic
sign of the correction factor in making the algebraic
addition. Use the following examples:

Example 1
If the measurement is made across 90 ohms, the
indication on the DECIBELS scale is +2, and the RANGE
switch is at the +30 DB position, the level in dbm is
obtained as follows:

The Impedance Correction Graph

3-3

TM 11-6625-1514-15

Section III

Paragraphs 3-22 to 3-25

+ 2 (meter indication)
+30

(RANGE switch position)
+32 (sum)
+8

(correction factor from the Impedance

+40 dbm

Example 2
For the same conditions as given above, except that
the measurement is made across an impedance of 60,000
ohms, the level in dbm is obtained as follows:

+ 2 (meter indication)
+30

(RANGE switch position)
+32 (sum)

-20

(Correction factor from the Impedance

+12 dbm

3-22. USE OF VOLTMETER AMPLlFIER.

3-23. The amplifier in the voltmeter may be used for
amplifying weak signals. With full-scale meter deflec­tion, the open-circuit output of the amplifier is approxi-

mately 0.15 volt rms regardless of the RANGE switch
position. The impedance looking into the OUTPUT
terminals is approximately 50 ohms. The frequency

Correction Graph)

Correction Graph)

response and calibration of the voltmeter may be
affected by the impedance of a load applied to the
OUTPUT terminals. To check the effect of the applied
load: observe the meter reading obtained with no load
connected to the OUTPUT terminals and then note any
shift of reading when the external circuit is connected
to the OUTPUT terminals. If the shift is negligible,
the measurement is not being affected appreciably by
the load. Whenever the input signal is changed, i.e., a
different frequency or band of frequencies is applied,
repeat the quick check described above.

3-24. Maximum gain from the amplifier is obtainable
only on the lowest (.001 volts) range, since output level
is the same for all bands. This is due to the 10-db
amplification loss per step inserted by the RANGE
switch as it is turned clockwise. Amplification may
also be obtained on the .003, .01, .03, and 1 volt ranges.

3-25. When the voltmeter is used as an amplifier,
select a range which gives a meter deflection near

full scale. Off-scale signals more than twice the value
of the position of the RANGE switch will cause severe
distortion.

3-4

00102-2

TM 11-6625-1514-15

Section III

Figure 3-4. Impedance Correction Graph

3-5

4-0

Section IV

TM 11-6625-1514-15

00102-2

Figure 4-1.

SECTION IV

CIRCUIT DESCRIPTION

4-1. BLOCK DIAGRAM.

4-2. The electrical circuits of the voltmeter are shown
in the block diagram in figure 4-1; they consist of an input
voltage divider controlled by the RANGE switch, a cathode
follower input tube, a precision step attenuator controlled
by the RANGE switch, a broadband amplifier, an indicat­ing meter, and a regulated power supply. The voltage
applied to the INPUT terminals for measurement is
divided by 1000 before application to the input cathode
follower when the RANGE switch is set to the 1-volt

range and higher; the input voltage is applied directly
to the cathode follower on the lower ranges. The voltage
from the cathode follower is divided in the precision
attenuator to be less than 1 millivolt for application to
the voltmeter amplifier.

is rectified in a full-wave bridge rectifier with a d-c

milliammeter across its midpoints. The resultant

direct current through the meter is directly proportional

to the input voltage.

4-3. INPUT VOLTAGE DIVIDER AND STEP

ATTENUATOR.

4-4. The input voltage divider limits the signal level

applied to the input cathode follower to less than 0.3

volt rms when voltages above this level are measured

with the RANGE switch set at the 1-volt range or above.

The divider consists of a resistive branch with one
element made adjustable to obtain exact 1000:1 division
at middle frequencies and a parallel capacitive branch
with one element made adjustable to maintain exact
1000:1 division to beyond 4 megacycles. The input

impedance of the voltmeter is established by this divider
and is the same for all positions of the RANGE switch.
On the six low-voltage positions of the RANGE switch,
the input divider provides no attenuation of the input
voltage. (See figure 5-10 for the complete schematic.)

4-5. The step attenuator in the cathode circuit of the
input cathode follower reduces the voltage to be measured

to 1 millivolt or less for application to the voltmeter

amplifier. Each step of the attenuator lowers the signal

level by exactly 10 db (1: 10). The attenuator consists

of six precision wirewound resistors which are selected

to very high accuracy and carefully mounted on a 12-

position rotary switch. The RANGE switch rotor has two
contractors (see figures 5-9 and 5-10); the first contacts
each resistor in turn while the input divider is in the
non-attenuating position; the second rotor finger repeats
these contacts while the input attenuator is in the attenu­ating position.
(C15) is automatically connected to provide flat frequency
response beyond 4 megacycles. In the .003- and the .01­volt ranges, separate adjustable capacitors (C14, C16)
are automatically connected to the attenuator to permit
setting the frequency response at 4 megacycles. C14 and
C16 are also connected to the attenuator on the 3- and
10-volt ranges.
connected) flattens frequency response on the .03- and
30-volt ranges.

00102-2

On the .001-volt range a fixed capacitor

Fixed capacitor C106 (permanently

The output of the amplifier

TM 11-6625-1514-15

Paragraphs 4-1 to 4-11

4-6. Cathode follower V1 provides a constant, high input
impedance to the input voltage divider and INPUT ter­minals of the voltmeter and provides a relatively low
impedance in its cathode circuit to drive the step at­tenuator.

4-7. BROADBAND VOLTMETER AMPLIFlER.

4-8. Amplification of the signal voltage is provided
by a four-stage stabilized amplifier consisting of tubes
V2 through V5 and associated circuits. The amplifier
provides between 55- and 60-db gain with about 55 db
of negative feedback at mid-frequencies. The feedback
signal is taken from the plate of the output amplifier (V5)
through the meter rectifiers and gain-adjusting circuit

to the cathode of the input amplifier (V2). Variable

resistor R107 in the feedback network adjusts the negative
feedback level to set the basic gain of the amplifier at
mid-frequencies, while adjustable capacitor C102 permits
setting amplifier gain at 4 megacycles. Variable resistor

R118 in the coupling circuit between V4 and V5 permits
adjusting the gain of the amplifier at 10 cycles per
second by controlling the phase shift of low-frequency
signals between these two stages (increasing phase
shift decreases degeneration and increases gain).

4-9. Variable resistor R119 in the grid return path for

V3, V4, and V5 adjusts the total transconductance of
these tubes in order to restrict the maximum gain­bandwidth product of the amplifier. The gain-bandwidth
product must be restricted to give a smooth frequency

response rolloff above 4 megacycles and to prevent
possible unstable operation at frequencies far above

4 megacycles when tubes having unusually high trans-

conductance are used (tube transconductance tolerances
during manufacture permit wide variations in new tubes;
the adjustment permits the use of such tubes). The

plate voltage from V5 is rectified by the meter rec­tifiers and drives the feedback network. The cathode

voltage of V5 is fed to the meter OUTPUT terminals

for monitoring purposes.

thus the signal voltage at the cathode, is affected by
the loading of the meter rectifiers. For signal levels

causing third- scale or more meter deflection, this dis-

tortion consists of a very small irregularity near 0 volts

on the waveform as each diode begins conduction.

4-10. INDICATING METER CIRCUIT.

4-11. The meter rectifier circuit consists of two silicon

diodes and two capacitors connected as a bridge with the

indicating meter across the mid-points as shown in

figure 4-2. The diodes provide full-wave rectification

of the signal current for operating the meter. Electron

flow through the meter is supplied in the following manner

(see figure 4-2). During the positive-going half cycle

of plate voltage on V5, rectifier CR1 conducts electrons

from both C32 and C33 back to the B+ buss. The portion

of electrons from C33 flows through the meter on the way
to B+. At this point in the cycle, both C32 and C33 are

charged to the potential of B+ less some small drop in

R51 and R52.

The voltage gain factor across V1 is 0.95.

The current through V5, and

Section IV

4-1

TM 11-6625-1514-15

Section IV
Paragraphs 4-12 to 4-16

4-12. During the negative-going half cycle of the plate
voltage of V5, rectifier CR2 conducts electrons back to
both C32 and C33 from the plate of V5. That portion
of electrons going back to C32 flows through the meter
on the way (in the same direction that the electrons
flowed in the first, positive, half cycle). At this point
in the cycle, both C32 and C33 are discharged. The
pulsating current through the meter is smoothed by
C34 to prevent meter pointer vibration when measuring
low-frequency signals.
the arithmetic average value of the waveform ampli­tude of the signal.
based on the mathematical ratio between the average and
rms values of true sine wave current.

4-13. In addition, the bridge serves as a segment of a
voltage divider (in series with L11 and R108) connected
across the output of the amplifier. The negative feedback
voltage fed to the input of the amplifier is obtained across
L11 and R108. The alternating charge and discharge of
C32 and C33 produce at their junction with L11 an al­ternating current of the same phase and waveform as
that at the plate of V5. This phase is negative with

respect to the input signal applied to the first stage of
the amplifier (V2), and drives the negative feedback
network.

4-14. POWER SUPPLY.

4-15. The power supply consists of tubes V6 through V8
and the associated circuits, as shown in the complete

The current is proportional to

Meter calibration in rms volts is

schematic diagram, figure 5-10. The power supply
furnishes regulated +250V d-c voltage for the grid and
plate bias circuits of tubes V1 through V5, unregulated

12.6V d-c voltage for the heater supply of tubes V1
through V4, and 6.3V a-c voltage for the heater supply
of tubes V5 through V8. The power supply is designed
to operate from either a 115-volt (±10%) or a 230-volt
(±10%) a-c power source of 50 to 1000 cps. The primary
winding of power transformer T1 is arranged in two
sections, which can be strapped either in parallel or in
series, to permit operation on 115V or 230V, respectively.

4-16. The output of rectifier V6 is applied to the voltage
regulator circuit consisting of V7 through V9 which
supplies a constant, +250 volts dc to the stabilized ampli­fier circuit of the voltmeter. Tube V7 is the series
regulator tube, and V9 provides a fixed reference voltage
drop, with which the output voltage is compared in ampli-

fier V8B. V8A is a cathode follower which couples the
reference voltage from V9 to V8B without loading V9.
The regulated output voltage is applied to the control
grid of V8B, while the reference voltage is applied to
its cathode. The difference between the control grid
and cathode voltages controls the operating point of
V8B and thus its plate voltage, which in turn supplies the
grid voltage for regulator V7. Any change in the regu­lated output of V7 produces a correcting change in the
grid bias of V7 through the action of V8B, thus maintaining
an essentially constant output voltage despite changes in
line voltage or load on the supply. The gain of V8B is
high enough to keep the output at the V7 cathode regulated

4-2

Figure 4-2. Simplified Schematic of Meter Bridge Circuit

00102-2

TM 11-6625-1514-15

Section IV

Paragraph 4-17

to within ±1 volt dc as the V7 plate voltage is varied ±10%,
with about 60 ma of load current. The response of the
regulating circuits is fast enough to reduce ripple in
the output voltage to less than 1 millivolt, supplementing
the filtering action of C30. C36 couples the ripple com­ponent in the regulated output directly to V8B to avoid
attenuation in R62. R57 shunts a small portion of the

load current around V7 to prevent excessive V7 plate
dissipation at high line voltages. R63 and C35 constitute
a low-pass filter which prevents noise generated in V9
from reaching V8B.

4-17. The heater supply for the voltmeter tubes is
divided into two sections. One section supplies d-c
voltage for the tubes in the input cathode follower and

the amplifier. The other section supplies a-c voltage
for the tubes in the power supply. The voltage required
for the heaters of tubes V1 through V4 is obtained from

6.3V and 7.3V secondary windings of transformer T1,
which are series connected. The voltage developed
across the two series-connected windings is rectified
by full-wave rectifier CR3, reduced to 12.6 volts by
R66 and R68 in parallel, and applied to the series­parallel-connected heaters of V1 through V4, as shown

in figure 5-10.
four heaters establishes a voltage of 6.3V for each.
The heater of V5 receives 6.3V ac from one of the wind-

ings which drives CR3.

V8 receive 6.3V ac from a separate 6.3V secondary
winding on T1.

The series-parallel connection of the

The heaters of V6, V7, and

00102-2

4-3

SECTION V

MAINTENANCE

TM 11-6625-1514-15

Section V

Paragraphs 5-1 to 5-8

5-1. SCOPE.

5-2. This section contains complete instructions for

repairing and calibrating the voltmeter. This material

is covered in the following groups of paragraphs: b. Do not remove tubes when the voltmeter is turned

Lead

Paragraph

5-3.
5-5.
5-7.
5-9.

5-10.
5-13.
5-17. Trouble Shooting
5-20. Testing the Power Supply
5-22.
5-24.

5-3. PRECAUTIONS.

5-4. Observe the following precautions:

a. Make no adjustments and replace no parts in the

voltmeter except as described in one of the following

INSTRUMENT TYPE
Electronic

Multimeter

Precautions
Test Equipment Required
Meter Zero Adjustment
Cabinet Removal
Tube Replacement
Replacement of Special Parts

Testing Voltmeter Performance
Calibration and Frequency Response

Adjustments

Topic

REQUIRED CHARACTERISTICS

0 to 300 a-c and d-c volts;
accuracy of ±3% or better;
input impedance 100 megohms.

procedures. If an adjustment or replacement of parts
is made without following instructions or understanding
the effects, further trouble shooting may be complicated.

on. Before replacing tubes refer to paragraph 5-10.

5-5. TEST EQUIPMENT REQUIRED.

5-6. The test equipment required for complete testing
of the voltmeter is listed in figure 5-1. Equivalent
instruments may be substituted for those listed.

5-7. METER ZERO ADJUSTMENT.

5-8. The meter is properly zero-set when its pointer

rests over the zero calibration mark on the meter scale

when the instrument is 1) at normal operating tempera-

ture, 2) in its normal operating position, and 3) turned
off. Adjust the zero-set if necessary, as follows:

a. Allow the voltmeter to operate for 20 minutes so
that the meter movement will reach normal operating
temperature.

b. Turn the voltmeter off and allow one minute for all

capacitors to discharge.

USE

Voltage and resistance ME -26 B/U or

measurement.

DESIGNATION

H-P 410B

Oscillator 10 cps to 300 kc; 3 volts

Voltmeter Calibrator
(Precision Voltage 0.001 to 300 volts at mid-frequencies.

Source)

Frequency 300-kc to 4-mc range;

Response 3 volts output into 50-ohm load; frequency response.

Test Set 10-db steps, 0 to 70 db.

Oscilloscope or

AC Voltmeter
Variable Adjust line voltage between 103

Transformer and 127V ac with 1-amp load.

D-C Current

Test Set

(Milliammeter)

00102-3

output into 50-ohm load. testing and calibration

400-cps output voltage;

in 10-db steps ±0.2%; 0.1 to

1.0 volt in 0.1 volt steps ±0.2%.

10-cps to 4-mc range.

Clip-on type measurement;
current range up to 100 ma. power supply.

Figure 5-1. Test Equipment Required

Signal source for

Calibrating voltmeter

Calibrating voltmeter

Trouble shooting by
signal tracing.

Checking voltmeter
operation with
varying line
voltage.

Checking load on

H-P 200S

H-P 738BR

H-P 739A

H-P 160B or
H-P 400D

CN-16/U or
Ohmite VT2

H-P 428B

5-1

TM 11-6625-1514-15

Section V

Paragraphs 5-9 to 5-16

c. Rotate mechanical zero-adjustment screw clock-

wise until meter pointer is to the left of zero and mov-

ing upscale toward zero.

d. Continue to rotate adjustment screw clockwise;

stop

when pointer is exactly on zero. If pointer over-

shoots zero, repeat steps c

e. When pointer is exactly on zero, rotate adjust-

ment screw approximately 15 degrees counterclock­wise.
screw from the meter suspension. If pointer moves

turned too far counterclockwise, repeat the procedure

This is enough to free the zero adjustment
during this step, because the adjustment screw is
of steps c

5-9. CABINET REMOVAL.

a. Remove the two cabinet retaining screws at the

rear of the instrument.

b. Push the instrument chassis forward out of the
cabinet. The bezel ring remains attached to the front
panel.

c. When replacing cabinet, pull power cable through
opening at rear of cabinet. Be sure power cable is

not caught between chassis and cabinet. Replace re-

taining screws.

5-10. TUBE REPLACEMENT.

5-11. In many cases instrument malfunction can be
corrected by replacing a weak or defective tube. Check
tubes by substitution while following the voltmeter

through d.

Do not remove tubes from the voltmeter when
power is applied.
voltmeter.

and d.

To do so may damage the

performance check procedure in paragraph 5-22. Re­sults obtained through the use of a “tube checker” can
be misleading.

instrument, mark the original tubes so they can be
returned to the same socket if they are not defective.

Replace only those tubes proven to be defective.

5-12. Figure 5-2 lists each tube in the voltmeter with
its function and the check or adjustment required if

the tube is replaced.

5-13. REPLACEMENT OF SPECIAL PARTS.

5-14. PRECISION RESISTORS AND INDUCTORS. Sev-

eral parts used in the voltmeter have closer tolerances
than those used in most test equipment. Resistors
R104, R105, R108, and R111 through R116 are pre-

cision components. If these resistors require replace-

ment, use the same value and type as the original, as

shown in the parts breakdown.
are used or component positions are moved, the cali­bration of the voltmeter may be inaccurate or the fre-

quency response may be altered. The inductance of

L10 and L11 affects the frequency response of the

voltmeter. Do not alter the shape or position of these

coils. Install replacement components in the same
positions the original components occupied, as nearly

as possible.

5-15. DIODE RECTIFIERS. Special high-performance

silicon diodes selected by the Hewlett-Packard Co.

are used for CR1 and CR2. When replacing the sili-

con diodes, be careful in soldering; heat can damage
them.

on each diode lead close to the diode body to conduct
the heat away.

voltmeter calibration and frequency response must
be checked as described in paragraph 5-22.

5-16. RANGE SWITCH. Because of the critical con-

struction and wiring of switch S1, it is not practical
to attempt a major repair on the switch. When mech-

anical failure occurs in switch S1, replace the complete

Place a heat sink (such as a long-nose pliers)

Before removing the tubes from the

If different values

If CR1 and CR2 are replaced, the

CIRCUIT

REF.

V1
V2
V3
V4
V5

V6
V7
V8
V9

* Note that V1 must be replaced by a 6CB6, aged and selected for low noise and microphonics

Part No. 5080-0621).

5-2

TYPE

6CB6*

6CB6
6CB6
6CB6
6CB6

6AX5

12B4A

6U8

5651

Figure 5-2. Adjustments Required When Tubes Are Replaced

FUNCTION

Cathode Follower

1st Amplifier
2nd Amplifier
3rd Amplifier
4th Amplifier

High Voltage Rectifier
Series Regulator
Control Tube
Reference Tube

Calibration and frequency response (para. 5-22)

Test of the power supply (para. 5-20)

CHECK OR

ADJUSTMENT

00102-3

switch assembly. Use the following procedure. (Locate
parts by referring to figures 5-3 and 5-4; RANGE switch
connections are shown in figure 5-9.)

a. Remove voltmeter cabinet. (See paragraph 5-9.)
b. Loosen setscrews in RANGE switch knob and

remove knob.

c. Disconnect capacitor C104 from switch S1.
d. Disconnect white leads from capacitors C14 and

C16. Label each lead with a tag.

e. Remove the two screws and one nut which retain

the switch shield plate.

f. Disconnect white leads from switch contacts. Tag

each lead to permit easy connection to the new switch.

g. Disconnect the heavy dark-green switch lead, the
heavy light-green switch lead, and the heavy black switch
lead at terminal strips. Tag each lead.

NOTE

The input shield must be removed for access
to the terminal board connection of the dark­green lead.

h. Remove the nut which holds the switch bushing to

the front panel.

i. Remove RANGE switch assembly.

j. The sequence for installing the replacement RANGE

switch assembly is the reverse of the removal procedure.

k. After replacement of switch S1, check the calibra-

tion and frequency response of the voltmeter and make

necessary adjustments.

5-17. TROUBLE SHOOTING.

5-18. The first step in trouble shooting is to learn

the nature of the symptoms of the malfunction with as

much detail as possible. Inspect the test setup being
used when symptoms of malfunction were observed, to
be sure that the source of trouble is not external to the
voltmeter. Then remove the voltmeter cabinet as
directed in paragraph 5-9 and inspect the circuits of
the voltmeter, looking for signs of overheating, deteri­oration, and physical damage or tampering. Check the
fuse. If the fuse is blown, try another fuse to see if it
blows; if it does, measure the d-c resistance of filter
capacitors C1, C17, C30, C39, rectifier CR3, and the
windings of transformer T1 to locate the short circuit
without applying power to the voltmeter.

5-19. If the voltmeter can be turned on safely (without
the fuse blowing), measure the line voltage applied to T1
and the voltmeter power supply output voltages (see
paragraph 5-20). Check the tubes of the power supply
if the regulated voltage is not the proper value or is
unstable. Use the procedures of figure 5-5 and the
tests described in paragraph 5-22 to learn the full
nature of the trouble symptom. Watch for marginal

TM 11-6625-1514-15

paragraphs 5-17 to 5-21

operation by operating the voltmeter at 103 and 127
line volts while making tests. Check the tubes in the
voltmeter amplifier. Measure the tube element voltages
at the tube sockets and compare readings with the values
shown in the voltage and resistance diagram in figure
5-8. Apply a test signal to the input and measure the
voltage of the test signal while tracing it through each
coupling network and each stage of amplification.

Compare readings with those shown in the block diagram,

figure 4-1. In figure 4-1, an a-c current probe, H-P

Model 456A, is recommended for the measurement of
a-c current in the meter circuit without breaking any
leads. If this current probe is not available, avoid

measurement of the a-c current. Check meter indica­tions as directed in paragraph 5-22 instead. An
oscilloscope may be used for observing test signal
waveshape and measuring amplitude, if desired.

5-20. TESTING THE POWER SUPPLY.

5-21. The regulated power supply produces a constant

+250 vdc to operate all the tubes in the amplifier section.

The stability of the voltmeter depends directly upon the
stability of the +250 volts from the supply. When the
supply is operating satisfactorily, the +250 volt output
remains constant and the ripple level on it remains less
than about 1 millivolt for line voltages between 103 and

127 volts. Weak tubes (V6, V7, and V8) are the usual
causes of instability. An unstable regulator tube is
indicated by excessive line frequency ripple and varying
output voltage as the line voltage is changed. Marginal
operation is indicated if a trouble symptom appears
only when a low or high line voltage is applied. To test
the complete power supply proceed as follows:

a. Connect the voltmeter to an adjustable line trans­former so the applied line voltage can be varied between
103 and 127 volts. Set line voltage to 115 volts, turn on
the voltmeter, and allow a five-minute warmup period.

b. Measure the d-c voltage between V6 (pin 8) and
ground. Normal value is 410 ± 10 volts with exactly
115 volt power line input. Lower line voltage 10% to
103 volts for 2 minutes.

drops below 360 volts, replace V6.

c. Measure the d-c voltage between V7 (pin 1) and

ground with line voltage adjusted to 115 volts. Cor­rect value is 250 ± 5 volts.

d. Vary line voltage from 103 to 127 volts. The d-c

voltage observed in step c must not change more than

± 1 volt. For wrong voltage and/or poor regulation,

replace V7, V8 or V9.

e. Measure the a-c voltage between V7 (pin 1) and
ground. Ripple voltage must be less than 3 mv for any
line voltage (103 to 127 volts). High ripple voltage is
caused by defective V8, V7, V6 or V9. Replace in

this order.

f. Measure the direct current in the lead from
V7 (pin 1) which must be less than 60 milliamperes.
If the current is much too high, the regulator circuit

will not function properly. Excessive current indicates

If the d-c voltage slowly

Section V

00102-2

5-3

TM 11-6625-1514-15

Section V

5-4

Figure 5-3. Left Side View of Voltmeter Chassis

00102-3

TM 11-6625-1514-15

Paragraphs 5-22 to 5-23

Section V

Figure 5-4. Right Side View of Voltmeter Chassis

a short circuit or partial short in the circuits of the
voltmeter amplifier section. A clip-on type milliam­meter should be used for this measurement.

g. If the output voltage is stable but is incorrect,
measure the resistance of R62 and R64. The ratio
of these two resistors determines what the output voltage

will be. If the value of one of these resistors is in-

correct and produces the wrong output voltage, replace
it with a resistor which provides the correct output
voltage.

h. Measure the d-c voltage across C39A which must
be 12.6 volts with a line voltage of 115 volts. If nec­essary, adjust R66 to obtain 12.6 volts. If the voltage

cannot be set to 12.6 volts, check the a-c voltage from
the associated transformer windings; also check CR3

and C39.

5-22. TESTING VOLTMETER PERFORMANCE.

5-23. The following test procedure checks the accuracy
and stability of the voltmeter at low and high frequencies

00102-3

and with low and high line voltages. It can be used for
comprehensive incoming inspection, for proof of per­formance, and for trouble shooting. If the readings are

within specifications during these tests, the voltmeter is

operating properly. This test is made without removing
the cabinet. Instruments used to test the accuracy of
the voltmeter (see paragraph 5-5) must be known to have

sufficient

as follows:

a. Connect the voltmeter as shown in figure 5-6.

(This setup measures calibration accuracy at mid­frequencies.)

b. Set the line voltage to 115 volts, turn the voltmeter

on and allow a 30-minute warmup period.

c. Check the instrument meter zero setting as in-

structed in paragraph 5-7.

set voltmeter RANGE switch to. 001, and set voltmeter
calibrator VOLTAGE SELECTOR switch to provide 0
volts output.

accuracy to make valid measurements. Proceed

d Connect the voltmeter to the voltmeter calibrator;

5-5

TM 11-6625-1514-15

Section V

TROUBLE

1. Power indicator lamp does not light.
a. Fuse F1 burned out.

b. Power indicator lamp DS1 defective.
c. Defective a-c power cable.
d. Power switch S2 defective.
e. Transformer T1 primary winding

terminals incorrectly connected. winding; rewire if necessary.

2. Fuse F1 blows immediately when Power switch S2 is operated to ON.
a. Tube V6 shorted. a. Replace rectifier tube V6.
b. Rectifier CR3 defective. b. Replace heater rectifier CR3.
c. Short circuit in transformer T1 or in

circuit wiring. windings. Replace transformer T1 if

3. Fuse F1 blows after Power switch S2 has been operated to ON and tube heaters have warmed up.
Short in power supply circuit. Check for short circuit at cathodes V6 and V7.

4. Power indicator lamp lights; voltmeter does not indicate on all ranges.
a. Power supply or voltage regulator a. Check tubes V6, V9, V7, and V8 in turn.

circuits defective. Check high-voltage winding of transformer

b. Rectifier CR3 or circuit component

defective.

c. Diode CR1 or CR2 defective.

5. Meter indication normal on low ranges (.001 to .3 volts). Meter sensitivity distorted on

high-voltage ranges (1 to 300 volts).

Compensated 1000:1 divider defective.

PROBABLE CAUSE

REMEDY

a. Replace fuse F1. If replaced fuse blows,

check items 2 and 3 below.

b. Replace power indicator lamp DS1.
c. Repair or replace power cable.
d. Replace Power switch S2.
e. Check connections of transformer T1 primary

c. Remove all tubes, and check transformer

defective. Check for short circuit.

Replace defective component.

T1. Replace defective component.

b. Check for 12.6 volts dc across output of

rectifier CR3, Check resistors R66 and R68.
If tubes V1 and V2 are not lighted, check
capacitor C39. Replace defective component.

c. Replace diode (paragraph 5-15).

Check C4 and R4. Replace defective component.

6. Meter indicates low on all ranges.
a. Low amplifier gain.

b. Diode CR1 or CR2 defective.

7. Meter indication unstable or erratic.
a. Power supply, circuit defective.

b. Amplifier tube V1, V2, V3, V4, and

V5 defective.

8. Meter indication normal on .001 and 1 volt range.

ranges (.003, .01, .03, .1, .3, 3, 10, 30, 100, and 300 volts).

Faulty RANGE switch S1.

Figure 5-5. Trouble-Shooting Procedure

5-6

a. Check B+ voltage (paragraph 5-20). Check

tubes V2 through V5 for low emission. If
any tube is replaced, check and recalibrate

the voltmeter (paragraph 5-22).

b. Replace diode (paragraph 5-15).

a. Check heaters and B+ voltage. Replace

defective component.

b. Check V1 through V5 for microphonics or

noise. If tube is replaced, check and

recalibrate the voltmeter (paragraph 5-22).

Meter sensitivity distorted on all other

Check switch contacts of S1. Replace RANGE
switch S1 if defective (paragraph 5-16).

00102-2

TM 11-6625-1514-15

Section V

Figure 5-6. Test Setup for Calibration Check and Adjustments

The residual reading on voltmeter must be no higher
than the residual reading obtained with voltmeter INPUT
terminated with a 10-megohm resistor and shielded to
prevent stray pickup. If the residual reading is higher
when connected to the calibrator, refer to paragraph 3-12.

e. Set the voltmeter RANGE switch to .001. Set the
voltmeter calibrator to provide. 001 volt rms (400 cps)
output. Record deviation of voltmeter reading from 1
on the voltmeter scale.

f. Set the voltmeter RANGE switch to 1. Set the
voltmeter calibrator to provide 1 volt rms output. Re­cord deviation of voltmeter reading from 1 on the volt­meter scale.

g. Still using the voltmeter l-volt range, reduce the
voltmeter calibrator output in 0.1 volt steps. Record
deviation of voltmeter readings from each 0.1 volt cali­bration mark.

h. Compare recorded deviations with the permissible
errors listed in the performance specifications in
figure 1-2.

i. Connect the voltmeter as shown in figure 5-7
and set line voltage to 115. (This setup measures
calibration accuracy at low and high frequencies.)

meter reading; it must not be higher than the residual

reading noted in step d.

k. Turn the frequency response test set RANGE

SELECTOR to EXTERNAL. Set the external oscillator

frequency to 400 cps; adjust the oscillator output level
to obtain a reading of .9 on the 0 to 1 VOLTS scale of
the voltmeter. Then adjust the METER SET control on
the frequency response test set to obtain a standard

meter indication at the SET LEVEL mark on the test

set meter.

l. Tune the external oscillator to 10 cps and adjust
its output level to keep the frequency response test set
meter reading at SET LEVEL. Do not adjust the METER
SET control as this would alter the fixed monitoring

point of the meter. Record the voltmeter deviation

from .9 on the scale. This reading must be between

0.85 and 0.95 to be within specifications.
m. Set the RANGE SELECTOR on the test set to 3-10

mc, set the FREQ. TUNING dial to 4, and adjust the
AMPLITUDE control to keep the frequency response

test set meter reading at SET LEVEL. Record the

voltmeter deviation from .9 on the scale. This reading
must be between 0.85 and 0.95 to be within specifications.
The gain and frequency response of the basic voltmeter
amplifier is now tested.

n. Repeat step m

Record voltmeter deviation from .9 on the scale.

using line voltages of 103 and 127.

j. Set voltmeter RANGE switch to .001. Set frequency
response test set OUTPUT ATTENUATOR to .001 to
measure the lowest voltmeter range; initially set
AMPLITUDE control for 0 volts output. Then note volt-

00102-3

o. Set voltmeter RANGE switch to .003 and also set
the frequency response test set OUTPUT ATTENUATOR
to .003 to check this voltmeter range. Repeat steps k

and m. Record voltmeter deviation from .9 on the scale.

5-7

TM 11-6625-1514-15

Section V
Paragraphs 5-24 to 5-26

Figure 5-7. Test Setup for Frequency Response Check and Adjustment

p. Set voltmeter RANGE switch to .01 and also set the

frequency response test set OUTPUT ATTENUATOR to

.01 to check this voltmeter range: Repeat steps k
Record voltmeter deviation from .9 on the scale.

q. Set voltmeter RANGE switch to 1 and also set the
frequency response test set OUTPUT ATTENUATOR
to 1. Repeat step k.

r. Turn the frequency response test set RANGE

SELECTOR to EXTERNAL. Set external oscillator
frequency to 20 kc and adjust output level to keep the
frequency response test set meter reading at SET

LEVEL. Record voltmeter deviation from .9 on the
scale.

s. Repeat step m

from .9 on the scale.

t. The voltmeter is now completely tested. If the

measurements made have shown the voltmeter reading
to be within the tolerances given in the performance

specifications in Section I, the voltmeter is operating
satisfactorily.

calibration and frequency response adjustments as

directed in paragraph 5-24.
5-8

and record voltmeter deviation

If operation is unsatisfactory, make

and m.

5-24. CALIBRATION AND FREQUENCY RESPONSE

ADJUSTMENTS.

5-25. Calibration and frequency response adjustments

may be required when components other than those in
the power supply circuit are replaced. After replacing
any of these components, carry out the voltmeter
performance test of paragraph 5-22 to see if adjustments
are necessary. If the voltmeter operates within specifi-

cations during the test of paragraph 5-22, with respect
to both calibration (at mid-frequencies) and frequency

response, no adjustments are needed. If operation at

mid-frequencies meets calibration specifications, only
the frequency response adjustments need be made.

Otherwise, make all calibration and frequency response
adjustments in the order listed in the following procedure.

5-26. Calibration of the voltmeter consists of five parts:

a. Setting the basic gain of the amplifier at 400 cps.
b. Setting the division ratio of the input attenuator

at 400 cps.

c. Setting the frequency response of the amplifier.
d. Setting the 4-mc frequency response of the step

attenuator.

00102-2

TM 11-6625-1514-15

Section V

Paragraph 5-27

e. Setting the 20-kc and 4-mc frequency response

of the input divider.

NOTE

It is important to follow the complete procedure
in the order given, instead of attempting individ­ual adjustments which might appear to correct
a certain fault in calibration.

5-27. Although a special voltmeter calibrator instrument
and frequency response test set (listed in paragraph 5-5)
are shown for calibrating the voltmeter, other precision
a-c voltage sources having the required accuracy may
be used for this calibration procedure. In the following
procedure, the mechanical meter zero-set and the
regulated B+ voltage must already be correctly set

(see paragraphs 5-7 and 5-20, respectively). Proceed

as follows:

a. Connect voltmeter calibrator and voltmeter under

test as shown in figure 5-6. (Do not turn on.)

b. Provide a ground-level input to the voltmeter to
check for stray pickup between the
the voltmeter calibrator controls as follows:

OUTPUT SELECTOR to 400~ RMS

RANGE SELECTOR switch to 1.5-5

VOLTAGE SELECTOR switch to 0

POWER switch to ON

c. Set the RANGE switch on the voltmeter under test

to .001 volt, and the Power switch to ON. Allow at

least a ten-minute warmup. Refer to paragraph 3-12

of this manual and to the manual for the Model 738BR
Voltmeter Calibrator for a procedure to test for ground
currents. Eliminate any ground currents by breaking
ground loops as directed in paragraph 3-12.

d. To test the .001 volt range, set the voltmeter cali-

brator to .001 volt and the voltmeter RANGE switch to

.001. If necessary, adjust R107 (figure 5-3) to obtain
a reading of exactly 1 on the 0 to 1 VOLTS scale on the
panel meter of the voltmeter under test. This sets the
gain of the amplifier at audio frequencies.

e. Set the RANGE switch on the voltmeter to the 1­volt range. Set the voltmeter calibrator to 1 volt, to

test this range. If necessary, adjust R101 (figure 5-3)
to obtain a reading of exactly 1 volt on the voltmeter.
This sets the division ratio of the input voltage divi­der at audio frequencies.

instruments by setting

h. Set the RANGE switch on the voltmeter under test

to .001.

i. Set the oscillator for 400 cps output frequency and
adjust its output level to obtain a reading at 0.9 on the
voltmeter scale.

j. Adjust the frequency response test set METER SET
control to obtain a meter reading at SET LEVEL on the
test set. This standardizes the monitoring point of the
output level.

k. Set the RANGE SELECTOR and FREQ. TUNING
controls of the frequency response test set for 4-mc
output frequency and adjust the AMPLITUDE control
to provide a reading at SET LEVEL on the meter.

l. If necessary adjust C102 (figure 5-3) to obtain a
reading at 0.9 on the voltmeter under test. This sets
amplifier gain at video frequencies.

m. While watching voltmeter under test, adjust the
frequency response test set FREQ. TUNING control
from 4 to 10 Mc while holding output level constant
with AMPLITUDE control. The frequency response
curve increases from 4 to approximately 6 Mc and
then drops off from approximately 6 to 10 Mc. The
frequency response of instrument is within specifi­cation if voltmeter reading remains in 0 to 0.92 range.
If not in specifications adjust R119 and repeat steps

through l.

g

Whenever R119 is adjusted, both lo- and hi-

freq. response is affected and must be retested.

n. Readjust oscillator and frequency response test
set for 20 cps output and a SET LEVEL indication on
the test set meter. If necessary adjust R118 (figure 5-4)
to obtain a reading at exactly 0.9 on the voltmeter under
test.

o. Repeat step n
meter reading between 0.85 and 0.95 (±5%). If 10 cps

response is outside this range, readjust R118 slightly

to bring 10 cps response within the specified limits.

p. Repeat the 400-cps to 4-mc frequency response
check (steps g
voltmeter and if necessary adjust C14 (figure 5-4) to
obtain a reading of 0.9 on the voltmeter at 4 mc.

q. Repeat the 400-cps to 4-mc frequency response
check (steps g
voltmeter and if necessary adjust C16 (figure 5-4) to
obtain a reading of 0.9 on the voltmeter at 4 mc.

through k) on the .003 volt range of the

through k) on the 0.01 volt range of the

NOTE

at a frequency of 10 cps, for a volt-

f. Connect the frequency response test set, the
oscillator, and the voltmeter under test as shown in
figure 5-7. Observe grounding precautions described
in step c.

g. On the frequency response test set, set the OUTPUT
ATTENUATOR to .001, the RANGE SELECTOR to
EXTERNAL, and turn the Power switch ON. This

adjusts the frequency response test set to provide an

output from the external oscillator for the voltmeter
.001 -volt range.

00102-4

r. On the 1-volt range of the voltmeter, measure
frequency response at both 20 kc and 4 mc using a
procedure similar to steps g
necessary adjust C4 (figure 5-3) to obtain a reading
of 0.9 on the voltmeter. At 4 mc if necessary pad the
value of R6 (figure 5-3) to obtain a reading between

0.85 and 0.95 (±5%). R6 consists of several resistors
connected in parallel. Increasing the value of one of
these resistors raises the meter reading at 4 mc. The
input shield must be in place on the voltmeter chassis
when making this reading.

through k. At 20 kc if

5-9

5-10

Section V

TM 11-6625-1514-15

00102-3

Figure 5-8.

TM 11-6625-1514-15

Section V

Figure 5-9. Diagram of RANGE Switch

5-11

00102-3

5-13

TM 11-6625-1514-15

Section V

Figure 5-10.

TM 11-6625-1514-15

Paragraphs 6-1 to 6-12

SECTION VI

INTRODUCTION TO ILLUSTRATED PARTS BREAK DOWN

Section VI

6-1. GENERAL

6-2. This Illustrated Parts Breakdown lists and des­cribes the parts applicable to the Vacuum Tube Volt-

meters, Models 400D, 400H, 400L, and H02-400D,
manufactured by Hewlett-Packard Co. The breakdown
consists of four sections as shown in the Table of Con­tents.

6-3. GROUP ASSEMBLY PARTS LIST. The Group
Assembly Parts List (Section VII) consists of the complete

Voltmeter divided into six main assemblies or components
as shown in the Table of Contents. Each assembly listed

is followed immediately by its component parts indented
to show relationship to the assembly.

6-4. Part numbers are used to identify parts. A MIL-

type part number or a typical manufacturer and part

number are listed for each vendor part in the Group

Assembly Parts List.

supplied by a different vendor, but in all cases the

Hewlett-Packard stock number remains the same. The

H-P Stock No. column is adjacent to the manufacturer

or military Part No. column.

6-5. The index numbers are numerically arranged in

the Group Assembly Parts List and are used mainly to

assist in locating a part in the Group Assembly Parts

List after it has been found in the Numerical Indexes

(Section VIII) or located on the figure which illustrates

that particular assembly.

6-6. The nomenclature of each part in the Group

Assembly Parts List is indented to indicate assembly
relationship. Each part is indented one column to the
right of the next higher assembly. When the details of

an assembly are shown on a different figure and parts

list, the nomenclature of that assembly is followed by
a parenthetical note stating in which figure and parts
list the details will be found.

6-7. Attaching parts are shown in the same indent as
the parts which they attach, and immediately following
the part. They are separated from the parts which they
attach by the words (ATTACHING PARTS). The attaching
parts are separated from the following assembly, or the
details of the assembly which they attach, by the symbol

When attaching parts are shown as attaching
two or more parts, the quantities of the attaching parts
are those required to attach the total number of the
assemblies or parts being attached.

6-8. The quantities listed in the “Units per Assy” column
of the Group Assembly Parts List are, in the case of
assemblies, the total quantity used in the Voltmeter
at the location indicated. In the case of component
parts indented under the assembly, the quantity listed
is the quantity used per assembly. The quantities
specified in any one entry, therefore, are not necessarily
the total used per complete Voltmeter. Refer to the

Numerical Indexes (Section VIII) for the total quantities

used per complete voltmeter.

00102-3

The actual part used may be

6-9. USABLE ON CODE. Part variations within the

voltmeters are indicated by a letter symbol or com-

bination of letter symbols in parentheses immediately
following the figure and index number in the same column.
An explanation of the symbols used is outlined below.
In cases where the “Usable on Code” column has been
left blank, parts listed apply to all models covered by

this book.

USABLE

ON CODE

D
H

L

H02

6-10. PART NO.

Numerical Index (Section VIII) is compiled in accordance
with the numerical part number filing system described
below:

a. Part number numerical arrangement starts at the
left-hand position of the part number and continues from
left to right, one position at a time, until part number
numerical arrangement is determined for all the part

numbers. In the Part No. Numerical Index the federal
stock number consists of a class code prefix followed
by a serial number or the part number; that is, when a
serial number has been assigned, the class code and
serial number form the stock number; when a serial
number has not been assigned, the class code and part

number form the federal stock number.

b. The order of precedence in the arrangement of

the part number is as follows:

Space (blank position in the number)

(1)
(2)

Dash (-)

(3)

Letters A through Z

(4)

Numerals 0 through 9
Alphabetical 0’s shall be considered as
numerical zeros

6-11.

In cases where the same part appears in several
assemblies and therefore has several different figure
and/or index numbers, the Part No. Numerical Index lists
the figure and index number of each appearance, and the
total quantity of the part used is given on the line with
the first figure and index number entry.

6-12. HEWLETT- PACKARD STOCK NO. INDEX. The
Hewlett-Packard Stock No. Index is a numerical index
of Hewlett-Packard stock numbers, arranged in alpha-

numerical form in the same manner as the Part No.

Numerical Index. The Hewlett- Packard Stock No. Index
follows the Part No. Numerical Index in Section VIII.

NUMERICAL INDEX. The Part Number

MODE L NUMBER

400D
400H
400L
H02-400D

6-1

TM 11-6625-1514-15

Section VI

Paragraphs 6-13 to 6-15

6-13. REFERENCE DESIGNATION INDEX. The Ref­erence Designation Index (Section IX) lists electrical
parts by reference designator and is compiled with
reference designators in alpha-numerical order. It
provides a convenient method for locating parts within
the Group Assembly Parts List when the reference
designator is known.

6-14. SOURCE CODING. Source coding as applied to
the Numerical Indexes has been assigned by Department
representatives.

SOURCE CODE DEFINITIONS

a. CODE “’P” -

CONTROL

(1) CODE “P” is applied to the parts which are

procured in view of relatively high usage. Code

“P” parts may be requisitioned and installed
by any maintenance level, unless followed by
the letter - “O”, which restricts requisition
and replacement to Depot (O&R) level only.

Restricted service manufacture is considered
practicable but only after an attempt has been

made to procure from Supply Sources. In lieu
of the procurement of “P” coded parts, the

Department may designate a Depot (O&R) level
activity to manufacture supply requirements
for the Program.

(2) CODE “P1” is applied to parts which are very

difficult or uneconomical to manufacture. Service

manufacture is considered impracticable. Code

“P1” parts may be requisitioned and installed
by any maintenance level, unless followed by the

letter -

replacement to Depot (O&R) level only.

PARTS UNDER INVENTORY STOCK

“O” which restricts the requisition and

(2) CODE “A1” is applied to assemblies made up of

two or more parts each of which carry individual
part numbers and description, and which may be
assembled only by activities having Depot (O&R)
facilities.

d. CODE “X” PARTS CONSIDERED IMPRACTICABLE

FOR MANUFACTURE OR PROCUREMENT

CODE “X” is applied to the Main Structural

(1)

Members or similar parts which, if required,

would suggest extensive aircraft or equipment

reconditioning.
coded “X” (wing spar caps, center section struc-

ture) should normally result in a recommendation

to retire the aircraft or equipment from Service.

(2)

CODE “X1” is applied to parts for which the
procurement of the next larger assembly is

justified; e.g., an integral detail part, such as

welded segments, inseparable from its assembly;
a part machined in a matched set; or a part of
an assembly which, if required, would suggest
extensive reconditioning of each assembly.

CODE “X2” is applied to parts which are neither

(3)

procured nor stocked. Activities requiring
such parts shall attempt to obtain from salvage;
if not obtainable from salvage, such parts shall
be requisitioned through normal supply channels
with supporting justification.

e. CODE * PARTS NOT PROCURED, MANUFACTURED

OR STOCKED

(1) CODE * applies to installation drawings, diagrams,

instructions or field service drawings, basic
drawing numbers which cannot be procured or
manufactured, and obsolete parts.

The need of a part, or parts,

b. CODE “M” MANUFACTURE, PARTS NOT PRO-

CURED

CODE “M” is applied to parts which are within

(1)

the facilities of any activity to manufacture.

Procurement and stocking are not justified in

view of the relatively low usage, or storage

and installation factors, of these parts. Needs

are to be met by local manufacture as required.

CODE “M1” is applied to parts which can be

(2)

manufactured only by utilizing the facilities of

the Depot (O&R) activity. Procurement and

stocking of these parts are not justified in view

of their relatively low usage and installation

factors. The needs of all activities are to be

met through salvage, or by Depot (O&R) level

manufacture.

c. CODE “A” ASSEMBLE - ASSEMBLY NOT PRO-

CURED

(1) CODE “A” is applied to assemblies made up of

two or more units each of which carry individual
part numbers and descriptions, and which may be
assembled by any maintenance level.

6-2

6-15. VENDOR’S CODE. Vendor’s code numbers have
been assigned in accordance with Federal apply Code
H-4-1. The vendor’s code appears in parentheses fol-

lowing the item name or within the description of each
item in the Group Assembly Parts List (Section VII).
The vendor’s codes used in this Illustrated Parts Break­down are listed below for convenience.

VENDOR’S CODE
CODE
04009

14655

14674

19701

24446

Arrow, Hart, and Hegeman Electric Co.,
Hartford, Corm.

Cornell Dubilier Electric Corp.,
South Plainfield, N.J.

Corning Glass Works,
Corning, N.Y.

Electra Mfg. Co.,
Kansas City, Mo,

General Electric Co.,
Schenectady, N. Y.

NAME AND ADDRESS

00102-3

TM 11-6625-1514-15

Section VI

CODE
28480

28520

35434

56289

70903

71400

71785

72765

72982

73734

75915

78189

81482

82577

NAME AND ADDRESS

Hewlett - Packard Co.,

Palo Alto, Calif.

Heyman Mfg. Co.,

Kenilworth, N.J.
Lectrohm, Inc.,

Chicago, Ill.
Sprague Electric Co.,

North Adams, Mass.
Belden Mfg. Co.,

Chicago, Ill.
Bussman Fuse,

Division of McGraw-Edison Co.,

St. Louis, Mo.

Cinch Mfg. Corp.,
Chicago, Ill.

Drake Mfg. Co.,

Chicago, Ill.

Erie Resistor Corp.,
Erie, Pa.

Federal Screw Products Co.,

Chicago, Ill.

Littlefuse, Inc.,
Des Plaines, Ill.

Shakeproof,

Division of Illinois Tool Works,
Elgin, Ill.

Cooperative Industries, Inc.,

Chester, N.J.
Hughes Aircraft Co.,

Culver City, Calif.

CODE
83330

83380

84411

85628

85682

86684

88044

91506

91637

91662

93519

96906

89849

NAME AND ADDRESS

Smith, Herman H., Inc.,

Brooklyn, N.Y.
Buckley, C. E.,

Leominster, Mass.

Good All Electric Mfg. Co.,
Ogalala, Nebr.

King Engineering Co.,
Baltimore, Md.

Ringel Bros.,
Newark, N.J.

RCA Electron Tube,

Division of Radio Corp. of America,

Harrison, N.J.

Aeronautical Standards Group,

Departments of Navy and Air Force,

Washington, D. C.

Augat Bros., Inc.,
Attleboro, Mass.

Dale Products, Inc.,

Columbus, Nebr.
Elco Corp.,

Philadelphia, Pa.
General Electric Co.,

Lamp Works,

Oakland, Calif.

Military Standards
St. Louis Blow Pipe and Heater Co., Inc.,

St. Louis, Mo.

00102-3

6-3

TM 11-6625-1514-15

Section VI

HOW TO USE THIS ILLUSTRATED PARTS BREAKDOWN

HOW TO FIND THE PART NUMBER IF THE MAJOR

ASSEMBLY IN WHICH THE PART IS USED IS KNOWN.

Turn to the Table of Contents and find the page

(1)

number for the major assembly in which the
part is used.

Turn to the page determined in step (1).

(2)

Locate the part and its index number on the

(3)

illustration.

Find the index number on the Group Assembly

(4)

Parts List page to determine the complete de-

scription.

HOW TO FIND THE ILLUSTRATION FOR A PART

IF THE PART NUMBER IS KNOWN.

(5) Refer to the Part No. Numerical Index in Section

VIII and find the part number.

(6) Turn to Section VII and find the first figure and

index number that was indicated in the Part No.

6-4

Numerical Index for that part. If this figure
shows the part in a major assembly other than
the one desired, refer to the other figure numbers
listed in the Part No. Numerical Index.

(7) On the face of the illustration, find the index

number determined in step (6).

HOW TO FIND THE PART AND ILLUSTRATION

NUMBER FOR AN ELECTRONIC OR ELECTRICAL

PART IF THE REFERENCE DESIGNATION IS KNOWN.

(8)

Refer to section LX, Reference Designation Index
and find the reference designation. The part
number and the figure and index number will be
shown in the right-hand columns opposite the
reference designation.

(9)

Turn to Section VII and find the figure and index

number shown for the part in the “FIG. AND
INDEX NO.” column of the Reference Designation
Index.

(10)

On the face of the illustration, find the index
number determined in step (9).

00102-2

SECTION VII

GROUP ASSEMBLY PARTS LIST

TM 11-6625-1514-15

Section VII

Group Assembly Parts List

7-1- (D)

00102-2

Figure 7-1.

400D
(H)
(L)
(H02)

-1

400H

400L

H02-400D

400D-44B

2520-0006

400D
400H
400L
H02-400D
400D-44B

AN526-832-10

400D/H/L Vacuum Tube Voltmeter

VACUUM TUBE VOLTMETER (28480) . . . 1
VACUUM TUBE VOLTMETER (28480) . . . 1
VACUUM TUBE VOLTMETER (28480) . . . 1
VACUUM TUBE VOLTMETER (28480) . . . 1

CABINET ASSEMBLY (28480) . . . . . 1

(ATTACHING PARTS)

SCREW, MACHINE . . . . . . . . .2

*

------

7-1

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

FIG. &

INDEX

NO.

7-1-

-2

-3

-4 0340-0089

-5

-6

-7 2140-0012

-8

-9

-10 0370-0035 0370-0035 ..

-11 (D, H02)
(H)

(L)

-12

-13 5020-0137

-14 (D, H02) 400D-2 400D-2 . .
(H, L)

-15

H-P MFR. OR MIL

STOCK

NO. NO.

2520-0003 AN526-832-8
2580-0003 510-081810-01

5060-0634
5060-0635 5060-0635 . . POST, BINDING, Black (28480) . . .

0340-0090
1450-0020

1450-0022

3101-0001

1120-0005
1120-0301
1120-0098
1400-0015

2360-0003

400H-2A

PART

NO NUMBER

5060-0634
0340-0089

0340-0090 . . INSULATOR, STANDOFF (28480) . .

14L-15
12

2020-AE
80994-H

1120-0005
1120-0301
1120-0098 . .
1550

5020-0137

AN515-6-4

400H-2A
NO NUMBER

DESCRIPTION

1234567

.

PANEL ASSEMBLY, FRONT

(ATTACHING PARTS)

SCREW, MACHINE . . . . . . . . . . . .

.
.

NUT, ASSEMBLIED WASHER (78189) . .

---*---

. .
.. INSULATOR, STANDOFF (28480) . .
. . LENS, INDICATOR LIGHT (72765) .

. .
. .

. .
.. MULTIMETER, REPLACEMENT . .
. . MULTIMETER, REPLACEMENT . .

..
. .

. .

.
.

POST, BINDING, Red (28480) . . . .

LAMP, INCANDESCENT, 6-8 VOLT,
2 pin base (93519)
LAMPHOLDER, 2 pin base (72765) .
SWITCH, TOGGLE, SPST (04009) . .
KNOB (28480)

(28480)
(28480)

MULTIMETER, REPLACEMENT . .
(28480)

CLAMP, LOOP (73734) . . . . . . .

BEZEL, INSTRUMENT MOUNTING
(28480)

(ATTACHING PARTS)

SCREW, MACHINE . . . . .

---*---

PANEL, FRONT (28480) . . . . . . .

PANEL, FRONT (28480) . . . . . . .

MAIN CHASSIS ASSEMBLY . . . . .

(See figure 7-2) (28480)

UNITS

PER

ASSY

1

5
1

2
2
2
2
1
1

1
1
1
1

1
1
1

1

6

1
1
1

7-2

00102-3

TM 11-6625-1514-15

Group Assembly Parts List

Section VII

FIG. &
INDEX

7-2-

-1

-2

-3 (D,H02)

-4

00102-3

NO.

(H,L)

Figure 7-2. Main Chassis Assembly (Sheet 1 of 2)

H-P

STOCK

NO.

0170-0002

1390-0020 INSULOID N3

2420-0001
0180-0063
0180-0033
400D-75H 400D-75H

2390-0009

MFR. OR MIL

PART

NO.

NO NUMBER

663UW20504

510-061810-01
30D120A1
30D133A1

COML

DESCRIPTION
1234567

MAIN CHASSIS ASSEMBLY (28480) . . . . . . REF

(See figure 7-1, index 15 for next higher
assembly)
.

CAPACITOR, FIXED, PAPER . . . . . . .

DIELECTRIC, 2.0 µf ±20%, 400 wvdc

(84411)

.

CLAMP, LOOP (85628) . . . . . . . . . .

.
.
.
.

.

(ATTACHING PARTS)

NUT, ASSEMBLED WASHER (78189) . . .

---*---

CAPACITOR, FIXED, ELECTROLYTIC, .

500 µf +100%, -10%, 3 wvdc (56289)
CAPACITOR, FIXED, ELECTROLYTIC, .
50 µf, 6 wvdc (56289)

BRACKET, CAPACITOR (28480) . . . . .

(ATTACHING PARTS)

SCREW, ASSEMBLED WASHER, . . . .

6-32 by 3/8 in. lg, s.s.

---*---

UNITS

PER

ASSY

2

3

3
1
1
1

1

7-3

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

FIG. & H-P

INDEX

NO. NO. NO.

7-2-

-7

-8

-9

-10

-11 1933-0004

-12

-13 1220-0005

-15 1200-0009

-16 1200-0008

-17

-18 2100-0080

-19

-20 0180-0028

-21 1930-0014

-22 1400-0033 120D5-63AHS

-23

-24

-25 (D,H,L)
(H02)

(H02)
(H02)

-26 9100-0050 9100-0050

STOCK

1220-0010
1923-0028
1940-0001
1921-0010

5080-0621

0180-0025

2100-0136 2100-0136

1200-0020
0400-0013
8120-0050

H02-400D- H02-400D-PWR­PWR-CORD

1251-0037

MFR. OR MIL

126
6CB6
5651
12B4
6U8

6CB6

429-.125

316PH-3702
44F-16388
D32452

2100-0080

D27390

6AX5-GT
51A12272

5P-1

CS-9941/PH151/

7.5 FT

CORD

CS-9941/PH151/ . .

7.5 FT W/O PLUG

MS24663

PART

DESCRIPTION UNITS

1

234567

.

SHIELD, ELECTRON TUBE (91662) . . .

.

ELECTRON TUBE (24446) . . . . . . .

.

ELECTRON TUBE (86684) . . . . . . .

.

ELECTRON TUBE (24446) . . . . . . .

ELECTRON TUBE (24446) . . . . . . . .

.
.

ELECTRON TUBE (24446)

.

BASE, Tube shield (91662) . . . . . . . .

.

SOCKET, ELECTRON TUBE (91662) . . .

.

SOCKET, ELECTRON TUBE (71785) . . .

.

CAPACITOR, FIXED, Electrolytic, .
4 section,20 µf per section,450 wvdc
(56289)

.

RESISTOR, VARIABLE, 1M ±30%, 0.2w . .
(28480)

.

RESISTOR, VARIABLE, 6K ±20%, 0.3w . .
(28480)

.

CAPACITOR, FIXED, ELECTROLYTIC, .

2 section, 1500 µf per section, 15 wvdc
(56280)

.

ELECTRON TUBE (86684) . . . . . . . .

.

RETAINER, ELECTRON TUBE (91506) .

.

SOCKET, ELECTRON TUBE (71785) . . .

GROMMET, PLASTIC (28520) . . . . . .

:

CABLE ASSEMBLY, POWER, . . . . . .

ELECTRICAL (70903)

CABLE ASSEMBLY, POWER, . . . . . .

.

ELECTRICAL (28480)

CABLE, POWER, ELECTRICAL (70003)
. .
.

CONNECTOR, PLUG, ELECTRICAL

(96906)
TRANSFORMER, POWER, STEP-DOWN
AND STEP-UP (28480)

PER

ASSY

1

5

1
1
1
1

1

6
2
3

1
1

2

1
1
1
1

1
1
1
1
1

-27

-28

-29

-30 400D-6J

-31

-32

7-4

2900-0001
0170-0057
0130-0006

0130-0001

2550-0007 COML

400D-6K 400D-6K

2390-0009 COML

400D-19A 400D-19A

510-101810-51
S70375
503-000-B2P0-28R
503-000-D2P0-33R
400D-6J

.
.
.
.

.

.

.

.

.

(ATTACHING PARTS)

NUT, ASSEMBLED WASHER (78189) . . .

---*---

CAPACITOR, FIXED, PAPER . . . . . .

DIELECTRIC, 5 µf ±10, 100 wvdc (56289)
CAPACITOR, VARIABLE, CERAMIC

DIELECTRIC, 5-20 pf, 500 wvdc (72982) .

CAPACITOR, VARIABLE, CERAMIC

DIELECTRIC, 7-45 pf, 500 wvdc (72982) .

SHIELD, ROTARY SWITCH (28480) . . .

(ATTACHING PARTS)
SCREW, ASSEMBLED WASHER, 8-32 by
3/8 in. lg, s.s.

---*---

BRACKET, ANGLE (28480) . . . . . . . .

(ATTACHING PARTS)
SCREW, ASSEMBLED WASHER, 6-32 by
3/8 in. lg, s.s.

---*---

RANGE SWITCH ASSEMBLY (28480) . .
(See figure 7-3)

4

1

1

1

1

2

1

2

1

00102-3

TM 11-6625-1514-15

Group Assembly Parts List

Section VII

FIG. &
INDEX

NO.

7-2-33

-34 0160-0024

-35

-36

-37

00102-3

Figure 7-2. Main Chassis Assembly (Sheet 2 of 2)

H-P MFR. OR MIL

STOCK

NO.

1400-0074 INSULOID C3

2390-0009 COML
3050-0100 AN960-6

2420-0001

1400-0016

2390-0001
2420-0001
0687-4711
0687-4741

PART

NO.

510-061810-01
PKM 4P5
781

COML
510-061810-01
RC20GF471K
RC20GF474K

DESCRIPTION
1234567
.

CLAMP, LOOP (85682) . . . . . . . . . .

.

.

.
.
.

.

.
.
.

(ATTACHING PARTS)
SCREW, ASSEMBLED WASHER, 6-32 by
3/8 in. lg, s.s.

WASHER, FLAT (88044) . . . . . . . . .

NUT, ASSEMBLED WASHER (78189) . . .

*

------

CAPACITOR, FIXED, PAPER
DIELECTRIC, 0.5 µf ±10%, 400 wvdc (14655)

CLAMP, LOOP (83330) . . . . . . . . .

(ATTACHING PARTS)
SCREW, ASSEMBLED WASHER, 6-32 by

1/2 in. lg, s.s. (78189)

NUT, ASSEMBLED WASHER (78189) . .

---*---

RESISTOR, FIXED, COMPOSITION, . .
470 ohm ±10%, 1/2w (ML-R-11)
RESISTOR, FIXED, COMPOSITION, . .
470K ±10%, 1/2w (MIL-R-11)

UNITS

PER

ASSY

1

1

1

1
1
1

1

1
2
2

7-5

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

FIG. &

INDEX

NO. NO.

7-2-38

-39 01504012

-40

-41 0890-2241 RC32GF224K

-42 0699-0005 RC32GF2R7K

-43

-44

-45 0180-0033

-46

-47 0170-0063 148P22394

-48

-49

-50

-51

-52

H-P

STOCK

400D-75G

2390-0009

0687-4701

0687-5611 RC20GF561K
0687-2751 RC20GF275K

0887-1041

0816-0017
0687-6841
0690-4731 RC32GF473K
0693-1031 RC42GF103K
400D-75F

MFR. OR MIL

400D-75G

COML

29C214A3-H-1038

RC20GF470K

30D133A1
RC20GF104K

C-10-6.3K
RC20GF684K

400D-75F

PART

NO.

DESCRIPTION

1234567

.

PRINTED CIRCUIT BOARD ASSEMBLY
(28480) (See figure 7-4)

(ATTACHING PARTS)

SCREW, ASSEMBLED WASHER, 6-32 by

.

3/8 in. lg, s.s.

---*---

CAPACITOR, FIXED, CERAMIC . . . .

.

DIELECTRIC, 0.01 µf ±20%, 1000 wvdc

(56289)

.

RESISTOR, FXXED, COMPOSITION, . . .
47 ohm ±10%, 1/2w (ML-R-11)

.

RESISTOR, FIXED, COMPOSITION, . . .
220K ±10%, 1w (MIL-R-11)

.

RESISTOR, FIXED, COMPOSITION, . . .

2.7 ohm ±10%, 1w (MIL-R-11)

.

RESISTOR, FIXED, COMPOSITION, . . .
560 ohm ±10%, 1/2w (ML-R-11)

.

RESISTOR, FIXED, COMPOSITION, . . .

2.7M ±10%, 1/2w (ML-R-11)

.

CAPACITOR, FIXED, ELECTROLYTIC,

50 µf, 6 wvdc (56289)

.

RESISTOR, FIXED, COMPOSITON, . . .
100K ±10%, 1/2w (ML-R-11)

.

CAPACITOR, FIXED, PLASTIC . . .
DIELECTRIC, 0.020 µf ±10%, 400 wvdc

(56289)

.

RESISTOR, FIXED, WIRE WOUND, . .

6.3K ±10%, 10w (35434)

.

RESISTOR, FIXED, COMPOSITION, . .

680K ±10%, 1/2w (MIL-R-11)

.

RESISTOR, FIXED, COMPOSITION, . .
47K ±10%, 1w (MIL-R-11)

.

RESISTOR, FIXED, COMPOSITION, . .

10K ±10%, 2w (MIL-R-11)

.

PRINTED CIRCUIT BOARD ASSEMBLY

(28480) (See figure 7-5)

UNITS

PER

ASSY

1

2

3

4
2
2
2
1
1
1
1

1

1
4
1
1

2360-0012
2190-0006
0380-0008
2420-0001

-53 0890-3321 RC32GFS32K

-54

-55 0689-1145

-56

-57

7-6

0160-0013

0893-8221 RC42GF822K
400D-6H 400D-6H

2420-0001

AN526-632-14
AN935-6
2102

510-081810-01

160P10494
RC32GF114J

510-081810-01

.
.
.

.
.

.

.
.
.

.

(ATTACHING PARTS)

SCREW, MACHINE (88044) . . . . . . . .

WASHER, LOCK (88044) . . . . . . . . .

SPACER, SLEEVE (83330) . . . . . . . .

NUT, ASSEMBLED WASHER (78189) . .

---*---

RESISTOR, FIXED, COMPOSITION, . .

3.3K ±10%,1w (MIL-R-11)
CAPACITOR, FIXED, PAPER
DIELECTRIC, 0.1 µf ±10%,400 wvdc (56269)
RESISTOR, FIXED, COMPOSITION, . .

110K ±5%, 1w (MIL-R-11)

RESISTOR, FIXED, COMPOSITION, . .

8.2K ±10%, 2w (MIL-R-11)
SHIELD, Input printed circuit board . .
assembly (28480)

(ATTACHING PARTS)

NUT, ASSEMBLED WASHER (78189) . .

*

------

2
2
2
2

1

2

1
2
1

2

00102-2

TM 11-6625-1514-15

Group Assembly Parts List

Section VII

FIG. &
INDEX STOCK

NO.

7-2-58

-59 0693-6821

-60 0170-0040

-61

-62

-63

-64

-65 1400-0025

-66 0761-0001

-67

-68

-69 0690-1001

-70

400D-65C 400D-65C

2390-0009

0687-2251

0687-8251 RC20GF825K
0160-0002
400D-6F 400D-6F

2420-0001

2420-0001

0687-1251

2100-0077 2100-0077

1882-0005 61-6911

H-P
NO.

MFR. OR MIL

PART

NO.

COML

RC42GF682K
148P47392

RC20GF225K

160P10396

510-061810-01
777

510-061810-01
N25-8.2K
RC20GF125K

RC32GF100K

DESCRIPTION
1234567
.

PRINTED CIRCUIT BOARD ASSEMBLY
(28480) (See figure 7-6)

(ATTACHING PARTS)

SCREW, ASSEMBLED WASHER, 6-32 by

.

3/8 in. lg, s.s.

---*---

.

RESISTOR, FIXED, COMPOSITION, . . .

6.8K ±10%, 2w (MIL-R-11)

.

CAPACITOR, FIXED, PLASTIC . . . .

DIELECTRIC, 0.047 µf ±10%, 200 wvdc

(56289)

.

RESISTOR, FIXED, COMPOSITION, . . .

2.2M ±10%, 1/2w (MIL-R-11)

.

RESISTOR, FIXED, COMPOSITION, . . .

8.2M ±10%, 1/2w (MIL-R-11)

.

CAPACITOR, FIXED, PAPER DIELECTRIC,

0.01 µf ±10%, 600 wvdc (56289)
MOUNTING PLATE, Shield (56289) . . .

.

.

.

.
.
.

.

.

.

(ATTACHING PARTS)

NUT, ASSEMBLED WASHER (78189) . .

---*---

CLAMP, LOOP (83380) . . . . . . . . . .

(ATTACHING PARTS)

NUT, ASSEMBLED WASHER (78189) . .

*

------

RESISTOR, FIXED, FILM, 8.2K ±5%, 1w .
(14674)
RESISTOR, FIXED, COMPOSITION, . . .

1.2M ±10%, 1/2w (MIL-R-11)
RESISTOR, VARIABLE, 4 ohm ±20%, 1w .
(28480)
RESISTOR, FIXED, COMPOSITION, . . .
10 ohm ±10%, 1w (MIL-R-11)
RECTIFIER, METALLIC (81482) . . .

UNITS

PER

ASSY

1

2

1
1

1
1
1
1

2
1

2

1
1
1
1
1

-71

-72

-73

-74 0690-1831

-75

-76 400D-1A

-77

00102-3

2370-0009
2420-0001

2110-0007

1400-0084

0687-3351

0160-0044

400D-1B

2110-0008

MS35239-42
510-061810-01

MDL-1
342014

RC20GF335K
RC32GF183K
160P27296

400D-1A
400D-1B

.
.

.
.

.
.
.

.
.

(ATTACHING PARTS)

SCREW, MACHINE (96906) . . . . . . . .

NUT, ASSEMBLED WASHER (78189) . .

---*---

FUSE, CARTRIDGE, 1 amp, 250v, slow .

blow for 115v (71400)

FUSEHOLDER (75915) . . . . . . . . . .

RESISTOR, FIXED, COMPOSITION,

3.3M ±10%, 1/2w (MIL-R-11)
RESISTOR, FIXED, COMPOSITION, . . .

18K ±10%, 1w (MIL-R-11)

CAPACITOR, FIXED, PAPER . . . . .

DIELECTRIC, 0.0027 µf ±10%, 600 wvdc
(56289)

PANEL, Rear (28480). . . . . . . . .

CHASSIS, ELECTRICAL EQUIPMENT .

(28480)
F1 fuse (230 v only) 1/2 amp

slow blow

1

1
1
1

1
1
1

1
1

7-7

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

7-8

FIG. &

INDEX

NO.

7-3-

-1

-2

-3

-4

-5

-6

H-P

STOCK

NO.

400D-19A

0140-0039
0887-1531
0150-0009

400D-26G

0140-0014
3100-0251

Figure 7-3. Range Switch Assembly

MFR OR MIL

PART

NO.

400D-19A

CM15E470J
RC20GF153K
315-000-C0G0-100D

400D-26G

CM15E560J

3100-0251

1234567

RANGE SWITCH ASSEMBLY (28480) . . . .

(See figure 7-2, index 32 for next higher

assembly)

.
.
.

.

.
.

DESCRIPTION

CAPACITOR, FIXED, MICA DIELECTRIC,
47 pf ±10%, 500 wvdc (MIL-C-5)

RESISTOR, FIXED, COMPOSITION, . . .
15K ±10%, 1/2w (MIL-R-11)

CAPACITOR, FIXED, CERAMIC . . . .

DIELECTRIC, 10 pf ±0.5 pf, 500 wvdc
(72982)
RESISTOR ASSEMBLY, Matched set of 6
wire wound resistors, replaceable only

as a set (28480)

CAPACITOR, FIXED, MICA DIELECTRIC,
56 pf ±10%, 500 wvdc (MIL-C-5)

SWITCH, ROTARY, Not separately . . .

replaceable (28480)

UNITS

PER

ASSY

REF

1
1

1

1

1
1

00102-2

TM 11-6625-1514-l5

Group Assembly Parts List

Section VII

Figure 7-4. Printed Circuit Board Assembly, Part No. 400D-75G

FIG. &
INDEX

NO. NO. NO.

7-4-

-1 0690-6831

-2

-3

-4

-5

-6

-7

00102-2

H-P MFR. OR MIL

STOCK

400D-75G 400D-75G

0687-1041 RC20GF104K
0730-0065
0730-0076
0690-1241
0690-5631
0693-1841 RC42GF184K

PART

RC32GF683K

DC-1-90.5K
DC-1-166K
RC32GF124K
RC32GF563K

DESCRIPTION
1234567
PRINTED CIRCUIT BOARD ASSEMBLY . .

(28480) (See figure 7-2, index 38 for next
higher assembly)

RESISTOR, FIXED, COMPOSITION, . . .

.

68K ±10%, 1w (MIL-R-11)

RESISTOR, FIXED, COMPOSITION, . . .

.

100K ±10%, 1/2w (MIL-R-11)
RESISTOR, FIXED, FILM, 90.5K ±1%, 1w .

.

(19701)

RESISTOR, FIXED, FILM, 166K ±1%, 1w .

.

(19701)
RESISTOR, FIXED, COMPOSITION, . .

.

120K ±10%, 1w (MIL-R-11)

RESISTOR, FIXED, COMPOSITION, . .

.

56K ±10%, 1w (MIL-R-11)

RESISTOR, FIXED, COMPOSITION, . .

.

180K ±10%, 2w (MIL-R-11)

UNITS

PER

ASSY

REF

1

1
1

1
1
1

1

7-9

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

FIG. &
INDEX

NO.

7-4-8

-9 400D-75G-2

-10

-11 0689-2425 RC32GE142J

-12

-13

-14 9140-0040 42µH-10%- COIL, RF, 42 µh ±10% (99849) . . . . . .

-15 400D-75G-1 400D-75G-1

H-P MFR OR MIL

STOCK

NO.

0690-3341

0140-0007 CM20B681K

0693-2731
0140-0025 CM15E680K

PART

NO.

RC32GF334K

400W75G-2

RC42GF273K

PHENOLIC FORM

DESCRIPTION

1234567

RESISTOR, FIXED, COMPOSITION, . . . 1

.

330K ±10%, 1w (MIL-R-11)

PRINTED CIRCUIT BOARD (28480) . . . 1

.

CAPACITOR, FIXED, MICA DIELECTRIC,

.

680 pf ±10%,500 wvdc (MIL-C-5)
RESISTOR, FIXED, COMPOSITION, . . . 2

.

2.4K ±5%, 1w (MIL-R-11)

. RESISTOR FIXED, COMPOSITION, . . . 4

27K ±10%, 2w (MIL-R-11)

CAPACITOR, FIXED, MICA DIELECTRIC,

.

68 pf ±10%, 500 wvdc (MIL-C-5)

“

PRINTED CIRCUIT BOARD (28480) . . . 1

.

UNITS

PER

ASSY

1

1
1

7-10

Figure 7-5. Printed Circuit Beard Assembly, Part No. 400D-75F

00102-2

TM 11-6625-1514-15

Group Assembly Parts List

Section VII

FIG. &

INDEX

NO.

7-5-

-1

-2 0170-0064

-3

-4

-5 400D-26C

-6

-7 0813-0009

-8

-9 0727-0018

-10

-11 1901-0027 HD-5004

-12 400D-75F-1

H-P MFR. OR MIL

STOCK

NO. NO.

400D-75F

0689-5105

400D-26F
2100-0108 2100-0108

400D-60A

0130-0002

0686-5115 RC20GF511J

400D-75F

RC32GF510J
148P47491

400D-26C
400D-60A

CS-2-125
557-000-U2P0-34R
DC-1/2C-40

400D-75F-1

PART

400D-26F

DESCRIPTION
1234567
PRINTED CIRCUIT BOARD ASSEMBLY . . REF

(28480) (See figure 7-2, index 52 for next
higher assembly)

RESISTOR, FIXED, COMPOSITION, . .

.

51 ohm ±5%, 1w (MIL-R-11)

CAPACITOR FIXED, PAPER . . . . . . . . . .

.

DIELECTRIC, 0.47 µf ±10%, 100 wvdc
(56289)
RESISTOR, FIXED, WIRE WOUND, . . .

.

10 ohm ±0.5%, 1/2w (28480)

.

RESISTOR, VARIABLE, 100 ohm ±30%, 1/3w

(28480)

RESISITOR, FIXED, WIRE WOUND, . . ,

.

205 ohm ±0.5% (28480)

COIL, RADIO FREQUENCY, 0.05 µh (28480)

.

RESISTOR, FIXED, COMPOSITION, . . .

.

125 ohm ±10%, 2w (91637)
CAPACITOR, VARIABLE, CERAMIC . . .

.

DIELECTRIC, 8-50 pf, 350 wvdc (72982)

RESISTOR, FIXED, FILM, . . . . . . .

.

40 ohm ±1%, 1/2w (19701)

RESISTOR, FIXED, COMPOSITION, . . .

.

510 ohm ±5%, 1/2w (MIL-R-11)
SEMICONDUCTOR DEVICE, DIODE (82577)

.

PRINTED CIRCUIT BOARD (28480) . .

.

UNITS

PER

ASSY

1

2

2

1
1

2

1
1
1
1

2

1

00102-2

7-11

TM 11-6625-1514-15

Section VII
Group Assembly Parts List

7-12

FIG. &
INDEX

NO.

7-6-

-1

-2

-3

-4

-5

-6

-7

-8

-9 0698-4116

-10

STOCK

400D-65C

0160-0005

0687-4701 RC20GF470K
2100-0151

0757-0839

0140-0084
0687-1001 RC20GF100K
0687-5601 RC20GF560K

0130-0003

400D-65C-1

Figure 7-6. Printed Circuit Board Assembly, Part No. 400D-65C
H-P
NO.

MFR. OR MIL

PART

NO.

400D-65C

160P47396

2100-0151

DC-1-10K
CM35E472J

503-000-C0P0-10R
DC-1-10.31M

400D-65C-1

1234567

PRINTED CIRCUIT BOARD ASSEMBLY . .

(28480) (See figure 7-2, index 58 for next

higher assembly)

CAPACITOR, FIXED, PAPER. . . . . . . . .

.

DIELECTRIC, 0.047 µf ±10%, 600 wvdc
(56289)

RESISTOR, FIXED, COMPOSITION, . . .

.

47 ohm ±10%, 1/2w (MIL-R-11)

RESISTOR, VARIABLE, 500 ohm ±20%, 1/5w

.

(28480)
RESISTOR. FIXED, FILM, 10 K ±1%

.

metal film 1/2 w (19701)

CAPACITOR, FIXED, MICA DIELECTRIC,

.

4700 pf ±5%, 500 wvdc (MIL-C-5)

. RESISTOR, FIXED, COMPOSITION, . .

10 ohm ±10%, 1/2w (MIL-R-11)

. RESISTOR, FIXED, COMPOSITION, . .

56 ohm ±10%, 1/2w, value selected at
factory, optimum value show (MIL-R-11)
CAPACITOR, VARIABLE, CERAMIC

.

DIELECTRIC, 1.5-7 pf, 500 wvdc (72982)
RESISTOR, FIXED, FILM, 10.31 meg ±1%

. metal film 1/2 w (19701)

PRINTED CIRCUIT BOARD (28480) . .

DESCRIPTION

UNITS

PER

ASSY

REF

1
1

1
1

1
1

2

1

1

1
1

00102-3

SECTION VII

NUMERICAL INDEXES

PART NO. NUMERICAL INDEX

TM 11-6625-1514-15

Section VIII

Numerical Index

00102-3

8-1

TM 11-6625-1514-15

Section VIII
Numerical Index

HEWLETT-PACKARD STOCK NO. INDEX

8-2

00102-3

SECTION IX

REFERENCE DESIGNATION INDEX

TM 11-6625-1514-15

Section IX

Reference Designation Index

00102-3

9-1

TM 11-6625-1514-15

Section IX
Reference Designation Index

9-2

00102-1

TM 11-6625-1514-15

Reference Designation Index

Section IX

00102-1

9-3

SECTION X

AUXILIARY EQUIPMENT

TM 11-6625-1514-15

10-1. General

10-2. Auxiliary equipment extends the opera­tion of the basic equipment, is not part of the
basic equipment, and is not required for normal
operation.

10-3. Line Matching Transformer Model

11004A

10-4. The Hewlett-Packard Line Matching

Transformer Model 11004A is specifically de-

signed to connect a balanced system to H-P

Model 200-series Audio Oscillators, H-P Model

Table 10-1. Specification

Frequency Range: 6 Kc to 600 Kc.
Impedance:

Primary:

balanced line.

Secondary: 600 ohms, unbalanced line

Terminating Resistance:

600 ohms or 10,000 ohms.

Insertion Loss: Less than 0.3 db at 100 Kc.

135 ohms ±10% or 600 ohms ±10%*

(secondary of transformer)

400-series Vacuum Tube Voltmeters, or similar
equipment, for carrier currents or other meas­urements between 5 Kc to 600 Kc. With a

Model 200CD it provides fully balanced 135­or 600-ohm output with attenuator in use.
With an H–P Model 400 it provides voltage
measurements on either 135- or 600-ohm bal­anced line without grounding one side, and
permits bridging or terminated voltage meas-

urements on both 135- and 600-ohm lines. The
Model 11004A Line Matching Transformer is

shown in Figure 10-1. Specifications are given

in table 10-1.

Frequency Response:

5 Kc and 600 Kc midfrequency value.

Balance: Better than 40 db over entire frequency

range.

Power Handling Capacity: +22 dbm (10 volts across

600 ohms).

Dimensions: 2 inches wide, 2 inches long, and 4 inches

high.

Weight: 12 oz.

Less than ±.5 db variation at

10-6. The Model 11004A is used to terminate
a 600-ohm unbalanced line to a 135- or 600-ohm
balanced line. A two-position toggle switch,

the 600

Ω -BRIDGING switch, provides termi-

nating or bridging voltage measurement capa-

bilities for 135- and 600-ohm lines.

Measurements can be made in dbm directly

for either 135 or 600

Ω connections provided

the line is terminated. However, accurate volt­age measurement can be read directly for the
600

Ω connection only. A schematic diagram of

the Model 11004A is shown in Figure 10-2.

The following rules will be helpful when de-

termining the position of the 600

Ω -BRIDGING

switch for various applications:

AGO 7945A

a. Use the BRIDGING position of the switch

(10K position) when bridging a balanced sys-

tem for measurement with an unbalanced line.

b. Use the BRIDGING position (10K posi-

tion) when driving a 600

Ω balanced system

with a single ended oscillator which has a 600­ohm output impedance.

c. Use the 600

Ω position of the switch when

terminating a balanced line into single ended
measuring instruments.

Note. When connecting the Model 11004A into a
system, the ground post (G) should be connected to
the grounded side of the measuring equipment.

10-6. The Model 11004A is designed to in­crease the usefulness of the H-P Models

10-1

TM 11-6625-1514-15

400D/H/L Vacuum Tube Voltmeters, the
Models 403A/B AC Transistor Voltmeter, the
Model 204B Transistorized Oscillator. In ad­dition, the Model 11004A can be used with the
405BR/CR Automatic DC Digital Voltmeter or
with the Model 457A AC-to-DC Converter (for
ac measurements to obtain digital measure­ments).

The instrument can be connected to the out­put terminals of a Model 200CD Wide Range
Oscillator to provide fully balanced output for
a 135-ohm or 600-ohm balanced line.

A typical setup for a 600-ohm balanced line
is shown in figure 10-3A; figure 10-3B shows
the connection for 135-ohm balanced line.

Figure 10-4 shows a typical bridging type

of measurement setup. The Model 11004A pro-

vides for voltage measurements on 135- or 600­ohm lines without grounding one side of the
line.

Voltage measurement in dbm (0 dbm = 1
mw in 600 ohms) on a balanced 135-ohm line
may be made without grounding one side of

the line.

The Models 200CD and 400D may be used

in conjunction with the Model 11004A to form
a signal generator for measurement in the
carrier frequency range. The Model 400D Volt­meter is connected across the output terminals

of the Model 200CD Oscillator to monitor the
output of the oscillator. The model 11004A
couples the oscillator to the balanced line. Fig­ure 10-5 shows the signal generator setup.

10-7. Bridging Transformer Model 11005A

10-8. The Hewlett-Packard Bridging Trans-

former Model 11005A operates at audio fre-

quencies to match or bridge single ended meas­uring instruments and signal generators to
balanced lines without disturbing the circuit

under test. The Model 11005A is shown in

figure 10-6; specifications are given in table

10-2.

The Model 11006A permits the use of single
ended VTVM’s such at the H-P Models
400D/H and 400L and Distortion and Wave
Analyzers such as the H-P Models 330B/C and

330D to work from balanced lines without dis­turbing the circuits under test. It will bridge
transmission lines at 10,000 ohms and is
equipped with a switch to allow 600-ohm line
termination.

10-9. When it is desired to terminate a bal­anced communications system into unbalanced
measuring equipment, described under para­graph 10-10, the Model 11005A satisfies the
dual requirements with the line terminated into
the primary with the switch in the 600-ohm
position. Figure 10-7 shows how the Model

11005A should be connected.

When measuring points with single ended in­struments along a balanced system operating
under normal conditions, the toggle switch
should be in the 10,000-ohm bridging position.

This prevents circuit loading and at the same

time satisfies the transition from the balanced

to the single-ended condition.
10-10. The following rules should be observed
when using the Model 11005A.

a. Use 10 K position when bridging a bal-

anced system for

measurements with single

ended instruments such as the H-P Model

330B/C/D Distortion Analyzers, Model 302A
Harmonic Wave Analyzer, Model 400D VTVM
or 400 H/L VTVM.

b. Use 10 K position when driving a 600

Ω

balanced system with a single ended oscillator
which has a 600-ohm output impedance such as
the 201C Audio Oscillator or an unbalanced
attenuator such as the H-P Model 200CD

Audio Oscillator.

c. Use 600

Ω position when terminating a

balanced line into single ended measuring in­struments.

d. Use 600

sistor as shown for 1000

Ω position with 400 Ω series re-

Ω unbalanced oscillator

(fig. 10-7) .

10-11. The Model 11005A contains a 10,000-

ohm bridging resistor across the secondary

winding of the transformer. The toggle switch
parallels this bridging resistance with a 638­ohm resistor when it is in the 600-ohm position
to present a 600-ohm match to the line.

10-2

AGO 7945A

Table 10-2. Specifications

Frequency Range: 20 cps to 45 Kc.

Impedance, Primary: 600 ohms.

Terminating Resistance:

600 ohms or 10,000 ohms.
Insertion Loss: Less than 1 db at 1 Kc.
Frequency Response: ±1 db, 20 cps to 20 Kc;

±2 db to 45 Kc.

Table 10-3. Replaceable Parts

H-P Part No.

0340-0090
0730-0011
0730-0029

1510-0006
1610-0007
3101-0001

1

Hewlett-Packard Co., Palo Alto, Calif.

2

Campbell Industries, Mahomet, Ill.

3

Arrow, Hart, and Hegeman Electric Co., Hartford, Conn.

I

Description Mfr
Insulator, binding post
R: fxd, 638 ohms, 1 w

R: fxd, 10 K ohms, 1 w
Binding post, black

Binding post, red
Switch, toggle

TM 11-6625-1514-15

Distortion: Less than 0.1%, 50 cps to 20 Kc;

Less than 0.5%, at 20 cps.
Balance: Better than 60 db.
Maximum Level: +15 dbm (4.5 volts at 600 ohms).

Size: 4 5/16" diam. 4 5/8" high overall.

Shipping Weight: 6 lbs.

1

28480

2

99459

2

94459

1

28480

1

28480

3

04009

I

Mfr part No.

0340-0090
obd#
obd#
1510-0006
1510-0007
obd#

TQ

4
1

1
1

3

1

AGO 7945A

Figure 10-1. 11004A line matching transformer.

10-3

TM 11-6625-1514-15

Figure 10-2. 11004A line matching transformer,

schematic diagram.

Figure 10-3A. Typical bridging type of 600-ohm setup

showing balanced to unbalanced line confirmation.

Figure 10-3B. Typical setup showing unbalanced to

135-ohm balanced line configuration.

Figure 10–4. Typical measurement setup.

Figure 10-5. Signal generator setup.

10-4

Figure 10-6. Model 11005A bridging transformer.

AGO 7945A

TM 11-6625-1514-15

Figure 10-7. Application of Terminals on 11005A Bridging Transformer.

10-8. Final Performance Check

a. Line Matching Transformer HP-11004A.

(1) Connect Generator HP 200 CD and
Voltmeter HP 400D to the secondary of the
transformer.

(2) Switch the transformer to the bridging
position, and adjust the generator for an output of 0

db at 100 KHz.

(3) Connect the meter to the 600 ohm primary
of the transformer. There should be less than 0.3 db
loss.

(4) Repeat the test in the range between 5 KHz

and 600 KHz. The reading should not vary more than

1 db.

b. Bridging Transformer Model 11005A.

Not applicable.

Change 1

10-5

DEPARTMENT OF THE ARMY

W

TM 11-6626-1514-15 is published for the use of all concerned.

By Order of the Secretary of the Army:

Official:

KENNETH G. WICKHAM,

Major General, United States Army,

The Adjutant General.

Distribution :

Active Army:

USAMB (1)

USACDCEC (1)
USACDCCEA (1)
USACDCCEA Ft Huachuca (1)
USASTRATCOM (8)
USASTRATCOM-PAC (5)
1st LOGCOMD (6)

2d LOGCOMD (6)
9th LOGCOMD (5)
Eighth USA (6)
SAAD (6)
TOAD (6)

LEAD (3)

HEADQUARTERS

ASHINGTON, D.C., 23 May 1967

HAROLD K. JOHNSON,

General, United States Army,
Chief of Staff.

NG: None

USAR: None

For explanation of abbreviations wed, see AR 320-50.

PIN :

019300-000