HP 8616a schematic

TM 11-6625-2820-14&P

TECHNICAL MANUAL

OPERATOR'S, ORGANIZATIONAL, DIRECT SUPPORT, AND

GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

FOR

SIGNAL GENERATOR SG-735 / URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6625-00-254-6671)

HEADQUARTERS, DEPARTMENT OF THE ARMY

JULY 1977

d-

●

*

TM 11-6625-2820-14&P

C2

CHANGE

HEADQUARTERS

DEPARTMENT OF THE ARMY

No. 2

Washington, DC, 1 January 1988

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT

AND GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

(INCLUDING DEPOT MAINTENANCE REPAIR PARTS AND SPECIAL TOOLS)

FOR

SIGNAL GENERATOR SG-735/URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6625-00-254-6671)

TM 11-6625-2820-14&P, 22 July 1977, is changed as follows:

Remove old pages and insert new pages as indicated below. New or changed material is indicated by a vertical bar

1.
in the margin of the page. Added or revised illustrations are indicated by a vertical bar adjacent to the identification
number.

Remove pages

Insert pages

iii and l-O . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..iii and l-O

5-17 and 5-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-17 and 5-18

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

Distribution authorized to the Department and DOD
for official use or for administration or operational purposes. This determination
was made on 1 October 1967. Other requests for this document will be referred
to Commander, US Army Communications-Electronics Command and Fort
Monmouth, ATTN: AMSE1-ME-P, Fort Monmouth, NJ 07703-5000.

contractors only

DESTRUCTION NOTICE – Destroy by any method that will prevent disclosure of
contents or reconstruction of the document.

By Order of the Secretary of the Army:

Official:

R.L. DILWORTH

Brigadier General, United States Army

The Adjutant General

DISTRIBUTION:

To

be distributed in accordance with DA Form 12-36 literature

requirements for SG-735/URM-165.

CARL E. VUONO

General, United States Army

Chief of Staff

TM 1 1-6425-2820-14&P

Cl

CHANGE

No. 1

HEADQUARTERS

DEPARTMENT OF THE ARMY

WASHINGTON, DC, 11 October 1978

Operator's, Organizational, Direct Support, and

General Support Maintenance Manual

Including Repair Parts and Special Tools Lists

(Including Depot Maintenance Repair Parts and Special Tools)

For

SIGNAL GENERATOR SG-735/URM-165

(HEWLETT-PACKARD MODEL 8616A)

(NSN 6626-00-254-6671)

This Changes is current as of 16 June 1978.

TM 11-6625-2820-14&P, 22 July 1977, is changed as follows:

1. The title is changed to read as shown above.

2. Remove old pages and insert new pages as indicated below.

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

Remove Pages

i. ii, and iii
6-9 through 6-12
111-3 and III-4
IV-1 and IV-2 (unnumbered)

4.

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

Insert Pages

i through iv
6-9

111-3 and III-4
IV-1 through IV-31

TM 11-6625-2820-14&P

By Order of the Secretary of the Army:

Official:

J.C. PENNINGTON

Brigadier General, United States Army

The Adjutant General

Distribution:

Active Army:

TSG (1)
USAARENBD (1)

USAINSCOM (2)
TRADOC (2)
DARCOM {2)
TECOM (2)
OS MAJ COMD (2)
USACC (2)
HISA (Ft Monmouth) (26)
Armies (1)
USASIGS (10)
Svc Colleges(1)
Ft Carson (5)
Ft Gillem (10)
Ft Huachuca (5)
Ft Richardson (CERCOM Ofc) (1)

WSMR(l]
USAERDAA (l)
USAERDAW (1)
Army Dep (1) except

LBAD (10)
SAAD (30)
SHAD (3)

(14)

TOAD
USA Dep (1)
Sig Sec USA Dep (1)
Units Org Under Fol TOE:

29-134

29-136

(1 cy each unit)

29-207

29-610

(2

copies each

unit)

BERNARD W. ROGERS

General, United States Army

Chief of Staff

ARNG:

None

USAR:

None

For explanation of abbreviations used, see AR 310-50.

U.S. GOVERNMENT PRINTING OFFICE: 1979-603-028/596

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

TM 11-6625-2820-14&P

ECHNICAL MANUAL

T

No. 11-6625-2820-14&P

OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, AND

GENERAL SUPPORT MAINTENANCE MANUAL

INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS

(INCLUDING DEPOT MAINTENANCE REPAIR

SIGNAL GENERATOR SG-735/URM-165

HEADQUARTERS

DEPARTMENT OF THE ARMY

WASHINGTON, DC, 22 July 1977

PARTS AND SPECIAL TOOLS)

FOR

(HEWLETT-PACKARD MODEL 8616A)

( NSN 6625-00-254-6671 )

REPORTING OF ERRORS

You can improve this manual by recommending improvements using DA
Form 2028-2 located in the back of the manual. Simply tear out the self ad­dressed form, fill it out as shown on the sample, fold it where shown, and drop
it in the mail.

If there are no blank DA Forms 2028-2 in the back of your manual, use the
standard DA Form 2028 (Recommended Changes to Publications and Blank
Forms) and forward to the Commander, US Army Communications and Elec­tronics Materiel Readiness Command, ATTN: DRSEL-ME-MQ, Fort Mon­mouth, NJ 07703.

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

This manual is an authentication of the manufacturer’s commercial literature which, through usage, has been
found to cover the data required to operate and maintain this equipment. Since the manual was not prepared
in accordance with military specifications, the format has not been structured to consider levels of main­tenance.

Change 1 i

TM 11-6625-2820-14&P

SECTION

0 INTRODUCTION . . . . . . . . . . . . . . . . .

I GENERAL INFORMATION . . . . . . . .

1-1.

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

1-6.

Supplementary Instruments . .

Instrument Options . . . . . . . . . .

1-9.

1-11. Instrument Identification. . . . .

1-13. Klystron Warranty Claim Sheet

II INSTALLATION . . . . . . . . . . . . . . . . . .

2-1. Incoming Inspection. . . . . . . . . .

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

2-3.
2-6. Conversion to Rack Mount. . .
2-7.
2-9.

Air Filter Inspection . . . . . . . .

Power Requirement . . . . . . . . . .

2-11. Three Conductor Power Cable. .

2-14. Repackaging for Shipment . . . .

III OPERATION . . . . . . . . . . . . . . . . . . . . .

3-1. Introduction . . . . . . . . . . . . . . . .

3-3. Controls and Indicators . . . . . . .

3-5. Operating Procedures. . . . . . . . .

3-7.

Stabilized Source . . . . . . . . . . . . .

IV PRINCIPLES OF OPERATION . . . . .

4-1. Introduction . . . . . . . . . . . . . . . .

4-3. RF Oscillator . . . . . . . . . . . . . . . .

4-6. Pin Diode Modulator . . . . . . . . .

4-16. Modulation Circuits. . . . . . . . . .

4-18.
4-20.
4-22.
4-25.

ExternalPulse . . . . . . . . . . . .

Internal Square Wave. . . . . . .

Extemal AM . . . . . . . . . . . . . .

Internal Meter and Automatic

Level Control (ALC) . . . . . . . .

4-36. External Leveling . . . . . . . . . .

4-37. Regulated Power Supply. . . . . .

V MAINTENANCE . . . . . . . . . . . . . . . . . .

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

5-1.

Test Instruments Required. . . .

5-3.

Periodic Maintenance. . . . . . . . .

5-5.
5-6.

Cleaning the Air Filter . . . . . .

5-8. General Maintenance . . . . . . .

5-10.

Cover Removal . . . . . . . . . . . .

6-12. Troubleshooting. . . . . . . . . . . . .

5-14. Repair . . . . . . . . . . . . . . . . . . . . .

6-16. Klystron Removal and

Replacement . . . . . . . . . . . . . .

6-17.
6-18.
6-19.

Tube Removal . . . . . .. o.....

Tube Replacement . . . . . . . . .

RF Probe Removal and

Replacement . . . . . . . . . . . . .

6-20.
6-21.
6-22.

Probe Assembly Removal . . .

Probe Replacement. . . . . . . . .

Pin Modulator Removal and

Replacement . . . . . . . . . . . . . . . .

5-23.

5-25.
6-26
5-27.

Modulator Removal . . . . . . . .

Modulator Replacement. . . . .

Calibration . . . . . . . . . . . . . . . . .

Regulated Power-Supply

Adjustment . . . . . . . . . . . . . . .

6-28.

Frequency Tracking,

preliminary. . . . . . . . . . . . . . .

6-29.

Power Adjustment . . . . . . . . .

Page

0-1

1-1
1-1
1-1

1-1

1-1

1-1
2-1

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

3-1
3-1
3-1
3-1
3-1

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

4-5
4-6
4-6

5-1
6-1
5-1
5-1
6-1

6-1
5-1
6-1
5-6

5-6
6-6
6-6

5-6
5-6
6-7

5-9
5-9
5-9
6-9

6-9

5-10
5-10

Illus

Figure

S

ECTION

6-30.

RF Power Output

Adjustment . . . . . . . . . . . . . . .

5-31. Meter Amplifier . . . . . . . . . . .

5-32. Frequency Tracking, Final . . . .

6-33.
5-34.
5-35.

ALC Amplifier . . . . . . . . . . . . .

Pulse Modulation Adjust. . . .

Square-Wave Adjust . . . . . . .

5-35A. AM Adjust . . . . . . . . . . . . . . . . .

6-36. Performance Checks. . . . . . . . . .

5-38. Frequency Range and

Accuracy . . . . . . . . . . . . . . . . .

5-39. AFControl Check . . . . . . . . . .

5-40.
5-41.
6-42.
6-43.

Power Output Check. ., . . . . .

Leveled Output Check . . . . . .

Pin Diode On-Off Ratio. . . . . .

Internal Square-Wave

Check . . . . . . . . . . . . . . . . . . . .

5-44.

5-45.

External Pulse Check . . . . . . .

External AM Check . . . . . . . .

5-46. Measurement of Residual and

Incidental FM . . . . . . . . . . . . .

6-47. Cam Cable Replacement . . . . . . .

5-48.
5-49.

Tools Required . . . . . . . . . . . .

Procedure . . . . . . . . . . . . . . . .

5-51. Low Pass Filter Replacement . .
5-52.

Tools Required . . . . . . . . . . . .

5-63. Procedure . . . . . . . . . . . . . . . .

5-65. Cavity Wiper Replacement . . . .

5-57.
5-59.

Parts Required . . . . . . . . . . . .

Replacement Procedure . . . . .

5-60. Frequency Drive Gear

Replacement . . . . . . . . . . . .

VI REPLACEABLE PARTS . . . . . . . . . . .

6-1.

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

6-3.

Abbreviations . . . . . . . . . . . . . . .

6-5.

Replaceable Parts List. . . . . . . .

6-7.

APP

ENDIX

Ordering Instructions . . . . . . . .

0 REFERENCES . . . . . . . . . . . . . . ..D

I MANUAL CHANGES . . . . . . . . . . . . . .

SECTION

I-1.

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

I-3.

Manual Changes . . . . . . . . . . . . .

I-6

Manual Changes Instructions . .

PPENDIX

A

II Illustrated Parts Identification . . . .

III MAINTENANCE ALLOCATION ... .

IV. ORGANIZATIONAL. DIRECT SUP-

PORT, AND GENERAL SUPPORT
MAINTENANCE REPAIR
PARTS AND SPECIAL

TOOLS LIST
(INCLUDING DEPOT
MAINTENANCE REPAIR
PARTS AND SPECIAL
TOOLS)

SECTION

I Introduction . . . . . . . . . . . . . . . . . . . . . .

II Repair Parts List . . . . . . . . . . . . . . . . . . .

Group

00 Signal Generator

SC 735/URM-165 . . . . . . . . . . . . . . . . .

Page Figure

Illus

6-10
5-12
5-12
5-13
5-14

5-14

5-14
5-14

5-14
5-14
5-15
5-15
5-15

5-15
5-17
5-17

5-18
5-18
5-18
5-18
5-21
5-21
5-21
6-21
5-21
5-21

5-24

6-1
6-1
6-1
6-1

6-1

0-1

i-1

i-1
i-1
i-3

ii- 1

III-1

IV-1
IV-6

IV-5

1

ii

Change 1

TM 11-6625-2820-14&P

SECTION

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . .

HighVoltagePower Supply . . . . . . . . . .

Control Panel . . . . . . . . . . . . . . . . . . . . . .

Leveler Assembly . . . . . . . . . . . . . . . . . .

Low Pass FilterAssembly . . . . . . . . . . .

01 Circuit Card Assembly,

HighVoltagePower

Supply A100 . . . . . . . . . . . . . . . . . . . . .

02 Circuit Card Assembly,

Low Voltage and

Figure
1-1,
2-1.
3-1.

3-2.

3-3.

3-4.
3-5.
3-6.
3-7.
3-8.
4-1.
4-2.

4-3.
4-4.
4-5.
4-6.
4-7.
4-8.
4-9.
5-1.

5-2.
5-3.

5-4.
5-5.
5-6.
5-7.
5-8.
6-9.
5-10.

Table

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

Mode 18616A SignalGenerator . . . . . . . . . . .

Conversion to RackMount . . . . . . . . . . . . . . .

Front and Rear Panel Controls

and Indicators . . . . . . . . . . . . . . . . . . . . . . .

Unleveled RF Power Output . . . . . . . . . . . . . .

Internally-Leveled RFOutput . . . . . . . . . . . .

Externally-Leveled RF Output . . . . . . . . . . . .

Internal Square-Wave Modulation . . . . . . . . .

External Pulse Modulation . . . . . . . . . . . . . . .

External FM Modulation...... . . . . . . . . . .

External AM Modulation...... . . . . . . . . . .

Circuit Block Diagram . . . . . . . . . . . . . . . . . .

Simplified Block Diagram of PIN

Modulator . . . . . . . . . . . . . . . . . . . . . . . . . . . .

RF Attenuator Unit . . . . . . . . . . . . . . . . . . . .

ALC Attenuator Unit . . . . . . . . . . . . . . . . . . .

Pulse ModulationCircuit . . . . . . . . . . . . . . . .

SquareWaveModulation Circuit . . . . . . . . . .

External AM Circuit . . . . . . . . . . . . . . . . . .

ALC and Meter Circuit . . . . . . . . . . . . . . . . . .

Series-RegulatedPower Supply . . . . . . . . . . .

Model 8616ABlock Diagram.. . . . . . . . . . . .

Cut-Away View of Klystron Cavity

and Klystron Assembly . . . . . . . . . . . . . . . .

RF Probe Assembly . . . . . . . . . . . . . . . . . . . .

PIN Modulator (Extemal View) . . . . . . . . . . .

Frequency Tracking Setup . . . . . . . . . . . . . . .

Frequency Tracking . . . . . . . . . . . . . . . . . . . .

Frequency and Power Measurement. . . . . . .

Internal Square Wave Check . . . . . . . . . . . . .

External Pulse Check........ . . . . . . . . . . .

External AM Check . . . . . . . . . . . . . . . . . . . . .

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .

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

Trouble Location . . . . . . . . . . . . . . . . . . . . . . .

Power SupplyAdjust . . . . . . . . . . . . . . . . . . .

Klystron Repeller Voltages . . . . . . . . . . . . . . .

Klystron Probe Adjust . . . . . . . . . . . . . . . . . .

ALC AmplifierAdjust . . . . . . . . . . . . . . . . . .

Illus
Page
IV-7
IV-9

IV-11
IV-15
IV-17

IV-19

Figure

7

ILLUSTRATIONS

Page

1-0

2-0
3-2

3-3
3-4
3-5
3-6
3-7
3-8
3-9
4-1

4-1
4-2
4-3

4-4
4-4
4-4
4-5
4-6
5-4

5-7

5-8

5-10
5-11
5-13
5-14
5-16
5-16
5-17

TABLES

Page

1-0

5-2
5-5
5-5

5-10
5-12
5-12

2
3
4
5
6

SECTION

ALC A500 . . . . . . . . . . . . . . . . . . . . . . . IV-23

03 Cavity Assembly . . . . . . . . . . . . . . . . . . . IV-27

04 Probe Assembly (No parts authorized)

SECTION

III Special Tools List

(Nonapplicable)

IV National Stock Number

and Part Number Index. . . . . . . . . . .

Figure
5-11.

5-12.
5-13.

5-14.

5-15.
5-16.
5-17.
5-18.
5-19.
5-20.
5-21.
A-1.
A-2.

B-1.

B-2.
B-3.
B-4.
B-5.

B-6.
B-7.
B-8.

Table

6-1.
6-2.
6-3.
A-1.
A-2.
A-3.

Top View, Cover Removed . . . . . . . . . . . . . . .

Residualand IncidentalFMChwk . . . . . . . .

ExplodedView-CamAsmmbly . . . . . . . . . . .

Low Pass FilterAsaembly Drawing . . . . . . . .

FormingtheCenter Conductor Fingers . . . . .

Modulation and Klystron Circuits . . . . . . . . .

ALCBoard (A500) . . . . . . . . . . . . . . . . . . . . . .

ALCCircuit . . . . . . . . . . . . . . . . . . . . . . . . . . .

Regulated +20Voltand Filament Supplies .

HighVoltageBoard(A100). . . . . . . . . . . . . . .

HighVoltagePower Supply . . . . . . . . . . . . . .

High VoltageBoard (A100). . . . . . . . . . . . . . .

Partial Schematic of Figure 5-17

ALC Circuit (Part of Change D) .......

HP Mode1 8616A, Signal Generator,

Generator Arrangement . . . . . . . . . . . . . . .

HP Model 8616A, Signal Generator,

Control Panel . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Cavity Assembly . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Probe Assembly . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

High Voltage Power Supply

Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Leveler Chassis . . . . . . . . . . . . . . . . . . . . . .

HP Mode1 8616A, Signal Generator,

Cabinet Assembly . . . . . . . . . . . . . . . . . . .

Reference Designations and Abbreviations .

Replaceable Parts . . . . . . . . . . . . . . . . . . . . . .

Manufacturers Code List . . . . . . . . . . . . . . . .

Manual Changes by Serial Number . . . . . . . .

Manual Changes by Assembly . . . . . . . . . . . .

8616A Recommended Changes . . . . . . . . . . .

Page

IV-28

Illus
Figure

8
9

Page

5-19
5-20
5-20
5-22
5-24
5-27
5-29
5-29
5-31
5-33

5-33

i-4
i-6

ii- 3
ii-5
ii- 7
ii-9

ii-11

ii-13
ii-15

ii-17

Page

6-2
6-4
6-9

i-2
i-2
i-7

Change 1 iii

TM 11-6625-2820-14&P

Figure 1-1. Model 8616A Signal Generator

Table 1-1. Specifications

Frequency Range:

4500 MHz.

Vernier:

MHz for fine tuning.

Frequency Calibration Accuracy:
Frequency Stability:

ambient temperature, less than 2500 Hz peak residual

FM, in a 10 kHz bandwidth, negligible incidental FM
in pulse and AM operation for attenuator settings be­low —10 dB. 0.003% change for line voltage variation
of ±10%.

RF output power:

3000 to 4500 MHz into a 50 load. Output attenua­tion dial directly calibrated in dBm from 0 to –127

dBm. A second uncalibrated output (approximately

0.5 mW) is provided on the front panel.

RF Output Power Accuracy (with respect to attenuation

dial:
Attenuator Accuracy:

–10 to –127 dBm: ±2 dB ±.06 dB/10 dB.

Leveled Output:

attenuation setting below 0 dB; ±l.0 dB.

Internal Impedance:

Modulation:

pulse.

Internal Square Wave:

cies available on special order.

External Pulse:

to +100V peak input.

F control has a range of approximately 1.5

±1.0 dB + attenuator accuracy (0 to –127 dBm).

direct reading within 2 MHz 1800 to

±10 MHz.

Approx. 0.005%/°C change in

+10 dBm (10 mW) +3 dBm from

for attenuation dial settings of

over entire frequency range at any

500; SWR less than 2.0.

On-off ratio at least 20 dB for square wave,

950 to 1050 Hz. Other frequen-

50 Hz to 50 kHz; 2 µsec rise time max +20

External AM:
External FM:

a. Front panel connector capacity-coupled to repeller

of klystron.

b. Four terminal rear panel connector (CinchJones

type S304AB) is DC-coupled to repeller of klystron.

Mode width between 3 dB points varies as follows: from

minimum of about 4 MHz to 5.5 MHz between 1800
and 3000 MHz to a maximum of about 8.5 MHz be­tween 3000 and 4500 MHz; klystron sensitivities are

about 100, 50, 200 and 100 kHz/V, respectively.

Power Source:

imately 125W.

Dimensions:

Weight:

DC to 1 MHz.

115 or 230V ±l0%, 50 to 60 Hz, approx-

net 48 lb. (22 kg).

1-0

Change 2

SECTION I

GENERAL INFORMATION

TM 11-6625-2820-l4&P

1-1. INTRODUCTION

1-2. The Model 8616A Signal Generator provides

RF power in the 1800- to 4500-MHz range. The
instrument produces an RF power output of at
least 2 mW. Output frequency and attenuation are
read directly on digital dials, and fine frequent y
changes can be made by means of the front-panel
A F control. Complete specifications are given in
Table 1-1. The 8616A is shown in Figure 1-1.

1-3. The instrument has two power output con-

nectors which supply RF power simultaneous y.
One output provides at least 10 mW (2 mW from

3000 to 4500 MHz) of power and may be leveled.

When in the leveled output mode of operation and
the output is 0 dBm or less, the RF output is held
quite constant across the band without resetting
the attenuator or power monitor. The other output
connector provides an uncalibrated output of at
least 0.5 mW. A wave-guide-beyond-cutoff attenua­tor, which is referenced to the RF output, accu­rately attenuates the calibrated RF power output
from O to –127 dBm.

1-4. RF power output can be internally square­wave modulated. In addition, the RF power can be
externally AM, FM, or pulse modulated. An exter­nal ALC (automatic level control) input which can
be used for remote leveling loop control and an

external DC-coupled FM input which can be used
for external AFC is also provided.

1-5. PIN diode attenuators are used for leveling,
square wave, pulse, and amplitude modulation. The
PIN attenuator is an absorption device that can be

electrically controlled to attenuate RF power. A
sampling loop which includes a PIN diode attenua­tor compensates for changes in RF power output
to hold the RF power output nearly constant.

1-6. SUPPLEMENTARY INSTRUMENTS

1-7. Two instruments capable of extending the
operating parameters
8403A and the Model 2650A. The Model 8403A
Modulator produces output pulses with 30 to 40

of the generator are the

nanosecond rise and decay time characteristics.
Pulse outputs are accurately variable in frequency,
width, and delay. Amplitude modulation is avail­able with frequency responses to 10 MHz for sine
waves. Square-wave frequency capability is accu­rately available. The modulator also provides sync
and delayed-sync outputs.

1-8. The Model 2650A Oscillator Synchronizer
may be used directly to stabilize all internal cavity
reflex klystron signal generators. Short-term sta­bility is one part in 108/sec, and long-term stability
is one part in 106/week over 0 to 50 degrees
centigrade.

1-9. INSTRUMENT OPTIONS

1-10. In addition to the standard instrument, the
option 01 is available. The option 01 instrument
has its input connectors located on both the front
and rear panel and its output connectors located
on, the rear panel; in all other respects it is the same
as the regular signal generator.

1-11. INSTRUMENT IDENTIFICATION

1-12, Hewlett-Packard uses a ten digit serial num­ber (on instrument rear panel) to identify instru­ments. The first four numbers and letter are the
serial prefix number and the last five digits are

unique to a specific instrument. If the serial prefix
on your instrument does not appear on the title
page of this manual, there are differences between
the manual and your instrument which are de­scribed in a Manual Change sheet included with the

manual. If the change sheet is missing, it may be

obtained, on request, from your nearest Hewlett-

Packard office.

1-13. KLYSTRON WARRANTY CLAIM SHEET

1-14. The klystron

klystrons purchased
guaranteed as set forth in the CONDITIONS OF
WARRANTY FOR KLYSTRON TUBES which is

found on the next to last page of this manual.

supplied and replacement

from Hewlett-Packard are

1-1

TM 11-6625-2820-14&P

2-0

Figure 2-1. Conversion to Rack Mount

SECTION II

INSTALLATION

TM 11-6625-2820-14&P

2-1.

INCOMING INSPECTION

2-2.

This instrument was inspected both mechani-

cally

and electrically before shipment. To confirm

this,

the instrument should be inspected for physi-

cal damage in transit.
accessories, and test the electrical performance of
the instrument, using the procedure outlined in
Paragraph 5-36. If there is damage or deficiency,
see the warranty on the inside rear cover of this
manual.

2-3. INSTALLATION

2-4. The Model 8616A is delivered as a cabinet
mount instrument. A kit is supplied with the

instrument for conversion from cabinet to rack
mount.

2-5. Whether the instrument is cabinet- or rack-

mounted, provision should be made for adequate
circulation of air around the instrument. The in­strument cooling fan is located at the rear of the
instrument and louvers are located on instrument
side panels. Proper air circulation is most impor-

tant at the sides and rear of the instrument.

IF FAN IS NOT OPERATING, THE
INSTRUMENT SHOULD NOT BE
OPERATED.

2-6. Conversion to Rack Mount

a.

Remove trim strip on sides of instrument

(refer to Figure 2-1).

Also check for supplied

2-7. Air Filter Inspection

2-8. The Model 8616A uses forced-air cooling to
maintain tolerable temperature within the instru­ment. Incoming air is filtered through a special

filter at the rear of the instrument. The air filter
should be checked periodically and if dirty,
cleaned. Refer to Paragraph 5-6 for air filter main­tenance.

2-9. POWER REQUIREMENT

2-10. The Model 8616A can be operated from a
115 or 230V, 50 to 60 Hz source. A two-position
slide switch (LINE VOLTAGE ) at the rear of the
instrument selects AC operation mode. The line

voltage at which the instrument is set to operate
appears on the slider of the switch. A 2 ampere
standard fuse is used for 115V operation; a 1
ampere standard fuse is used for 230V operation.

2-11. THREE-CONDUCTOR POWER CABLE

2-12. To protect operating personnel, the National
Electrical Manufacturer’s Association (NEMA)

recommends that the instrument panel and cabinet

be grounded. This instrument is equipped with a
three-conductor power cable which, when plugged
into an appropriate receptacle, grounds the instru­ment. The offset pin on the power cable three­prong connector is the ground wire.

2-13. The protection provided by grounding the
instrument cabinet may be lost if any power cable
other than the three-pronged type is used to couple
the ac line voltage to the instrument.

b. Remove tilt stand by pressing two sides of
stand toward center of instrument and lifting it
out.

c. Remove five feet at bottom of instru­ment. Press button in center of each foot, slide
them toward center of instrument, and lift out.

d. Place rack mounting flanges (two) where

trim strips were and secure with screws provided.

e.

Add filler strip to bottom of instrument.

f.

Rack mounting under
conditions must be supplemented with additional
support at rear.

severe vibration

2-14. REPACKAGING FOR SHIPMENT

2-15. The following list is a general guide for
repackaging an instrument for shipment. However,
if you have any questions, contact your local HP
field office.

If possible, use the original container de-

a.

signed for the instrument. If a carton and packing

materials are desired, they can be ordered from
your local HP field office.

b. The instrument is supported by four poly-

ethylene supports fitted to the instrument height:

one support located at each corner.

2-1

TM 11-6625-2820-14&P

NOTE

If the instrument is to reshipped to the
Hewlett-Packard Company for service or
repair, attach to the instrument a tag
identifying the instrument by owner,

model, and full serial number, and indi­cating the service or repair to be accom­plished. In any correspondence, refer to
the instrument by model number and
complete serial number.

2-2

SECTION Ill

OPERATION

TM 11-6625-2820-14&P

3-1. INTRODUCTION

3-2. The Model 8616A can provide 1.0 mW of
leveled power across its frequency range (RF out­puts leveled to within ±1.0 dB can be obtained
across the band for attenuator setting of 0 dB or
less). Output power can be attenuated to –127 dB.
When operating unleveled, attenuation reference is

the klystron power output; when operating leveled,
attenuation reference is output reference setting.
Internal square-wave modulation is available from
950 to 1050 Hz. External FM, AM, and pulse
modulation voltages also can be used. Two or three
modulation modes of operation can be applied to
the instrument simultaneously; push-button con­trols select the mode of operation. External modu­lation signal inputs are located directly below the
modulation to which they apply.

RF power in excess of approximately

125 mW should never be applied to RF
power output
damage could result.

3-3. CONTROLS AND INDICATORS

3-4. Front and rear panel controls and connectors
are shown in Figure 3-1. Each control and connec­tor is identified with a numbered call-out, and an
explanation of the function, given in the accom­panying text, is keyed to the call-out number.

connectors as internal

3-5. OPERATING PROCEDURES

3-6. The operating procedures Figures 3-2 through
3-8) give step-by-step procedures for the various
modes of operation.
obtaining the following leveled and unleveled out­puts: CW, square-wave modulated (modulating
voltage supplied internally, and FM, AM, and
pulse-modulated (modulating voltage supplied
externally ). Steps of each procedure are numbered
according to the sequence in which they are to be
performed, and any control or connector used is
identified with the number of the step in which it
is used.

3-7. STABILIZED SOURCE

3-8. To use an 2650A Oscillator Synchronizer
with the Signal Generator, proceed as follows:

The rear panel connector EXT FM (J201)

a.
is a Cinch-Jones type S304AB. Connection be­tween this jack and J5 of the 2650A must be made
as follows:

Pin 3, J201, to Pin E, J5, 2650A
Pin 4, J201, to Pin F, J5, 2650A
Pin 1, J201, to Pin G, J5, 2650A
Pin 2, J201, no connection

Connect RF output from UNCAL

b.
OUTPUT connector on Model 8616A to OSCIL­LATOR INPUT connector on Model 2650A. De­press EXTERNAL FM button on Model 8616A
and proceed as explained in the instruction manual
for the Model 2650.

Instructions are given for

3-1

TM 11-6625-2820-14&P

1.

LINE. Connects primary power to instrument;

lamp glows.

RF. Applies power to RF POWER OUTPUTS.

2.

ATTENUATION (dB). Sets RF power level at

3.
CAL RF POWER OUTPUT.

4.

UNCAL RF POWER OUTPUT.

mately 0.5 mW unleveled and unattenuated RF

power.

FREQUENCY (MHz). Sets

5.

F. Permits small deviations from FREQUENCY

6.
setting (±1.5 MHz).

ZERO SET. Adjust for zero indication on dBM

7.

meter (with RF turned off).
ALC. Levels calibrated RF output; used to set a

8.
reference on dBm meter.

INTERNAL SQ WAVE.

9.
PUT. SQ WAVE control adjusts modulation fre­quency.

Modulates CAL RF OUT-

Provides approxi-

RF frequency.

EXTERNAL PULSE.

10.
pulse input will provide modulation voltages re-

quired to pulse modulate CAL RF OUTPUT.
Positive pulses turn RF “ON

11.

EXTERNAL FM. AC

FM input will provide frequency modulation of
both CAL and UNCAL outputs.

12.

EXTERNAL AM.

input will provide modulation voltages required to
AM modulate CAL RF OUTPUT.

13.

INPUT REMOTE LEVELING. Input jack for

external leveling loop voltage applied to level
generator CAL RF POWER OUTPUT.

14.

LINE. Male receptacle which connects to the

power cord.

LINE VOLTAGE. Arranges input power trans-

15.
former to accept either 115 or 230 volt, 50 to 60
Hz primary power input.

16.

OPTION 01.

on rear panel (input connectors also located on
front panel).

17.

EXT FM:

lystron for stabilization of output frequency.

Input and output connectors located

Four terminal connector DC-coupled to

Positive pulses to external

voltages applied to external

Signals applied to external AM

3-2

Figure 3-1. Front and Rear Panel Controls and Indicators

TM 11-6625-2820-14&P

Depress LINE; lamp glows,

1.
Note meter pointer on dBm meter.

2.
Depress RF; there should be some deflection of dBm meter pointer.

3.

When RF button is depressed, meter pointer will fluctuate from
approximately +1 dBm at low frequency to +4 dBm or more at high
frequency.

4.

Set FREQUENCY (MHz) to desired frequency.
The ATTENUATION (dB) knob will attenuate RF power at CAL RF POWER OUTPUT.

5.
Take unleveled but attenuable RF power at CAL RF POWER OUTPUT.

6.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

7.

8.

Use A F control when a small deviation from FREQUENCY (MHz) setting is desired.

F control should be centered when not in use.

indicating heater and high voltage are applied.

NOTE

NOTE

Figure 3-2. Unleveled RF Power Output

3-3

TM 11-6625-2820-14&P

1.

Depress LINE.
Check that meter pointer on dBm meter is on ZERO SET mark; if not, adjust accordingly.

2.

Depress RF and INTERNAL ALC; there should be some deflection of dBm meter pointer.

3.

4.

Set FREQUENCY (MHz) low frequency.

Adjust ALC CAL OUTPUT control for desired dBm reference on dBm meter. The ALC system

5.

holds RF output power across the band to within ±1.0 dB for levels of 0 dBm or less. The
most common reference used is —10 dBm because the attenuated RF output power can be read
directly from attenuator readout. Leveled RF output power can be obtained across the band;
however, ATTENUATION (dB) will not accurately calibrate above –10 dBm.

NOTE

Power may be leveled above 0 dBm over that portion of the band where
the desired power is available.

6.

Set ATTENUATION (dB) to desired attenuation. The RF power level at CAL RF POWER
OUTPUT is the algebraic sum of the dBm meter setting and of the ATTENUATION (dB)
setting.

Take leveled and attenuable RF power available at CAL RF POWER OUTPUT.

7.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

8.

9.

Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

3-4

Figure 3-3. Internally-Leveled RF Output

TM 11-6625-2820-14&P

Depress LINE.

1.
Check that meter pointer on dBm meter is on ZERO SET mark.

2.
Depress RF and INTERNAL ALC.

3.
Set FREQUENCY for 1800 MHz.

4.
With a directional coupler connected between CAL output and the load, and as close to the

5.
load as possible, sample and detect incident power and apply the detected signal to INPUT
REMOTE LEVELING phone jack connection (rear panel). Approximately 40 mV but not
more than 240 mV is necessary.

Adjust ALC CAL OUTPUT for desired reference on dBm meter. This reference point may vary

6.
from that used with internal leveling due to different detector sensitivities.

Adjust ATTENUATION (dB) for desired attenuation.

7.
unless a 0 dBm reference has been set while monitoring with a power meter.

Take leveled and attenuable RF power available at CAL RF POWER OUTPUT.

8.
Take unleveled and unattenuable RF power at UNCAL RF POWER OUTPUT.

9.
Use F control when a small deviation horn FREQUENCY (MHz) setting is desired.

10.

The attenuator is not direct reading

Figure 3-4. Externally-Leveled RF Power

3-5

TM 11-6625-2820-14&P

1. Depress LINE.

NOTE

When unleveled power is to be modulated, omit steps 2, 5 and 6.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter.

7. Set ATTENUATION dB.

8. Depress SQ. WAVE.

9. Adjust SQ WAVE for desired modulation frequency.

10. Take leveled and attenuable RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY MHz setting is desired.

NOTE

F control should be centered when not in use.

3-6

Figure 3-5. Internal Square- Wave Modulation

TM 11-6625-2820-14&P

1. Depress LINE.

NOTE

If external pulse modulation of unleveled power is desired, omit steps 2,
5and6.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter.

7. Set ATTENUATION (dB) as desired.

8. Depress EXTERNAL PULSE.

9. Apply +20 to +100V 50 Hz to 50 kHz positive pulse modulating signal to EXTERNAL PULSE
INPUT.

10. Take leveled and attenuable pulse modulated RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

Figure 3-6. External Pulse Modulation

3-7

TM 11-6625-2820-14&P

Depress LINE.

1.

If external FM modulation of unleveled power is desired, omit steps 2, 5, and 6.

NOTE

Check that meter pointer on dBm meter is on ZERO SET mark.

2.
Depress RF.

3.
Set FREQUENCY (MHz).

4.
Depress INTERNAL (ALC).

5.
Adjust ALC CAL OUTPUT for desired dBm reference on dBm meter. The ALC system holds

6.
the RF output power across the band to within limits at frequencies up to 1 kHz provided the
FM voltages are small enough to maintain operation in the center of the mode. The most

common reference used is —10 dBm because the attenuator RF output power can be read
directly from attenuator readout.

NOTE

Power may be leveled above 0 dBm over that portion of the band where the desired power is available.

Set ATTENUATION (dB).

7.
Depress EXTERNAL FM.

8.
Apply modulating signal to EXTERNAL FM INPUT (front or rear panel).

9.
Take leveled and attenuable frequency modulated RF power output at CAL RF POWER

10.
OUTPUT.

Take unleveled FM-modulated RF power at UNCAL RF POWER OUTPUT.

11.
F control should be centered so that the klystron will operate in the center of the mode.

12.

3-8

Figure 3-7. External FM Modulation

TM 11-6625-2$20-14&P

1. Depress LINE.

2. Check that meter pointer on dBm meter is on ZERO SET mark.

3. Depress RF.

4. Set FREQUENCY (MHz).

NOTE

If AM modulation of unleveled power is desired, omit steps 5 and 6 and
proceed to step 7. Also, unleveled power can be AM-modulated with a

dc coupled audio signal.

5. Depress INTERNAL ALC.

6. Adjust ALC CAL OUTPUT control for at least 3 dB of attenuation. Due to leveIing at the
frequency desired, the ALC system holds the RF output power across the band to within limits
except for variations due to an AM signal. The most common reference used is —3 dBm because
this allows AM signal to modulate the RF above (3 dB) this level.

7. Set ATTENUATION (dB).

8. Depress EXTERNAL AM.

9. Apply AM modulating signal to EXTERNAL AM INPUT (6 volts peak-to-peak).

10. Take AM-modulated and attenuable RF power output at CAL RF POWER OUTPUT.

11. Use F control when a small deviation from FREQUENCY (MHz) setting is desired.

NOTE

F control should be centered when not in use.

Figure 3-8. External AM Modulation

3-9/3-10

SECTION IV

PRINCIPLES OF OPERATION

TM 11-6625-2820-14&P

4-1. INTRODUCTION

4-2. Basically the intrument includes a RF
Oscillator, PIN Diode Modulator, Automatic Level­ing Circuit, Modulation Circuits, and Power Supply
as shown in Figure 4-1. The RF Oscillator is a

reflex klystron which always operates CW. The PIN

diode modulator is a current-controlled device that
attenuates RF power up to 20 dB or more. The
control circuits provide the modulation currents

required by the PIN modulator. The power supply

provides the regulated dc voltages required to
operate the circuits in the instrument.

4-3. RF OSCILLATOR

4-4. The RF Oscillator, which generates the RF
power, consists of a velocity-modulated tube
operating in an external resonant cavity. The tube
is a reflex klystron operating in the 1-3/4 and 2-3/4
modes.

4-5. The RF power output from the oscillator,
which may be CW or CW with FM, is obtained
from the resonant cavity by means of pickup
probes located in

which open into the resonant cavity. One of these

probes delivers RF power directly to the UNCALI­BRATED RF OUTPUT connector, the other two

deliver RF power to the PIN modulator.

small sections of waveguide

4-6. PIN DIODE MODULATOR

4-7. The PIN modulator, which is two nearly
identical units in one, is a high-speed, current­controlled absorption-type attenuator. One unit,
the RF attenuator unit, is shown in Figure 4-3. The
second unit, the ALC attenuator unit, is shown in
Figure 4-4. It is a comparison unit. A simplified
illustration of the modulator is shown in Figure
4-2. Each PIN diode unit includes a transmission
line, PIN diodes, low-pass filter, and high-pass
filters.

Figure 4-2. Simplified Block Diagram

of PIN Modulator

Figure 4-1. Circuit Block Diagram

4-8. The PIN diode is a slice of nearly Pure silicon
wafer in which the P and N traces are nearly equal.
P-type impurities are diffused from one side into
the wafer, and N-type impurities are diffused from
the other side, leaving a layer of intrinsic semi­conductor (silicon) through the middle. Thus the
name, PIN diode. At frequencies below 100 MHz
the PIN diode rectifies the same as any other good

junction diode. However, at frequencies above 100

MHz, rectification efficiency drops rapidly because
of carrier storage in the intrinsic (I) layer.

4-9. When forward-bias current flows through the
PIN diode, holes and electrons are stored in the I
layer. The more the bias current, the larger the
amount of stored charge-carriers. When reverse bias
is applied, reverse current flows until the stored
carriers are depleted. During this period, the diode
impedance remains 10 w. Currents above several
hundred megacycles do not flow in the reverse
direction for a long enough time to remove those
charge carriers.

So, microwave currents

do not

4-1

TM 11-6625-2820-14&P

Figure 4-3. RF Attenuator Unit

significantly change the instantaneous amount of
charge carriers stored, and there is negligible recti­fication.

4-10. There is, however, a resistance to microwave
current flow. This resistance is inversely

proportional to the number of charge carriers
stored in the I layer, and the number of charge
carriers, in turn, is proportional to the forward bias
current. By varying the bias on a diode from back
bias (no stored charge) to about 1/2 mA forward
bias, the resistance to microwave currents varies
from approximately 5000 ohms to 30 ohms.

4-11. Pin Diodes Mounted in a Transmission

Line.

works, consider a PIN diode mounted across a

transmission line that has a characteristic impe­dance of 50 ohms. When the diode is back-biased
to about 5000 ohms, the microwave signal on the

transmission line is unattenuated because 5000

ohms compared to 50-ohm line impedance has

little effect. However, when the diode is

To understand how a PIN modulator

4-2

forward-biased to about 30 ohms, most of the

microwave current will flow through the 30-ohm
diode instead of propagating down the 50-ohm
transmission line. This current through the 30-ohm
diode represents microwave energy dissipated as
heat. Consequently the diode actually absorbs

microwave energy.

4-12. Figures 4-3A and 4-4A show the schematic

of the PIN diode modulator used in the Model

8616A. The PIN modulator contains seven PIN
diodes which are placed at approximately 1/4

wavelength along each strip transmission line. The

1/4 wavelength at midband spacing results in the
lowest average SWR because reflection from one
diode will tend to be absorbed and cancelled by

the adjacent diode. The resistance in series with the

diodes reduces voltage to the diodes and thereby

protects the circuit.

4-13. Modulation input in the form of diode bias

is used to change attenuation of the PIN diodes.

TM 11-6625-2820-14&P

Figure 4-4. ALC Attenuator Unit

Changes in diode bias produce changes in RF
output level.

4-14. Modulation circuits external to the PIN
modulator are protected by a low-pass filter (Fig-

ures 4-3 and 4-4 ) which prevents RF leakage.

Leakage, if present, could cause erratic action in
the circuits driving the PIN modulator and also
cause RF interference.

4-15. The high-pass filters (Figures 4-3 and 4-4)
permit RF energy to enter and leave the diode strip
line, while keeping the low frequency modulating
signals from entering the RF circuits preceding or
following the PIN modulator.

4-16. MODULATION CIRCUITS

4-17. The arrangement of the modulation circuits
depends on the mode of operation. Mode of
operation switching is accomplished by depressing
the appropriate front-panel button.

4-18. External Pulse

4-19. A simplified diagram of the circuits used in
the external pulse mode of operation is shown in
Figure 4-5. When the pulse button is depressed,
V401A is cut off, and V401B is conducting. The
conduction of V401 B draws current through the
PIN diodes in the REF attenuator unit; hence,
conduction of V401B forward biases the PIN
diodes causing the RF output to decrease by more
than 20 dB. A positive pulse applied to the exter-

nal pulse input turns V401A on, turns V401B off,
and allows RF power to pass through the PIN
diode attenuator with the RF output level clamped
to set level by CR403.

4-20. Internal Square Wave

4-21. A simplified diagram of the circuits used in
the internal square wave mode of operation is
shown in Figure 4-6. When V401B is conducting,
capacitor C402, is

discharging toward

4-3

TM 11-6625-2820-14&P

Figure 4-5. Pulse Modulation Circuit

approximately
cut off. When C402 discharges sufficiently, V401 A
begins to conduct and biases V401 B off through
the common cathode resistor R408. This results in
C402 charging toward approximately –225 volts as
long as V401A conducts. When C402 charges
sufficiently however, the current in V401A be­comes limited and V401B again conducts causing
V401A to cut off. The RC time constant of C402
is varied by R413, allowing frequency to be
changed from 950 to 1050 Hz. When V401B is
conducting the RF output is cut off by the PIN
diodes. The symmetry of the sqaure wave is ad-

justed by R410. R410 varies the voltage difference

across C402; by varying R410, the time for C402
to charge or discharge to a given potential is
controlled.

4-22. External AM

4-23. A simplified diagram

the external AM mode of

Figure 4-7. With the square

of operation off, V401B is cut off, causing con­duction of CR403 which isolates the square wave
and pulse circuit from the AM input and the PIN
diodes. Diode CR403 does this by clamping the

–200 volts while holding V401A

of the circuits used in

operation is shown in

wave and pulse modes

Figure 4-6. Square Wave Modulation Circuit

voltage at the junction of R414 and CR404 at
approximately +0.6 volt. This back biases CR404
providing the isolation.

Figure 4-7. External AM Circuit

4-4

TM 11-6625-2820-14&P

4-24. Since the PIN diode modulator is of the

absorption type, it is necessary to lower the aver­age level of the RF carrier (CW power level) by an
amount equal to the peak level of the AM signal so
that the peak will not be clipped. The ALC CAL
adjust sets the power level of the RF carrier. The
external signal then increases or decreases the
attenuation to give amplitude modulation. When
the external signal goes positive, it increases the RF
out of the generator by reducing the current in the

PIN diodes. A negative signal causes an increase in

current in the PIN diodes, which causes a signal

level reduction up to approximately 20 dB on the
negative half cycle of the input depending on
peak-to-peak amplitude of the AM signal. For most
purposes this amount of signal reduction should be
sufficient since it very nearly approximates 10070
modulation. The amount of distortion, though

small, is dependent upon the percentage of modu-

lation: at 30% modulation the amount of distor­tion is almost unnoticeable; at 100% modulation
the distortion may be as great as 5 to 20%.

4-25. Internal Meter and Automatic Level Control

(ALC)

4-26. A simplified diagram of the ALC circuit is

shown in Figure 4-8. The meter amplifier is a dual
function circuit, performing both a leveling and/or
a power output monitoring function. RF power is
taken from the klystron cavity through the ALC

attenuator assembly (part of the PIN diode modu­lator) and delivered to the ALC circuit. The meter
amplifier monitors the power level and in leveled
operation with the ALC amplifier, maintains a
constant RF output.

4-27. Actual operation is as follows: RF power

from the klystron is coupled from a fixed probe in
the klystron cavity to the ALC attenuator (part of
the PIN diode modulator). The RF power is deli-

vered through a high-pass filter to the ALC diode

attenuator, then through another high-pass filter to
a crystal detector. The detected signal from CR701
is then delivered to a low-pass filter and to the
ALC circuit.

4-28. The crystal detector CR701 is arranged so

that the detected signal is negative in polarity. An
increase in RF level as the klystron is tuned across
the band will cause a more negative output. A
decrease in RF power from the klystron causes a
less negative output. The detected RF output level
from CR701 is then delivered to the base of
Q501A.

4-29. Consider the circuit operation when the RF

level from the klystron increases. An increase in
klystron output level causes a more negative signal
on the base of Q501A. The conduction of Q501A

decreases causing the collector of Q501A to go in a

positive direction. The positive signal goes through

Figure 4-8. ALC and Meter Circuit

4-5

TM 11-6625-2820-14&P

the cathode follower, V401, and is applied to the
base of Q502, decreasing the conduction of Q502.
The collector of Q502 goes more negative.

4-30. A portion of the negative-going signal from

the collector of Q502 is applied to the base of
Q501B as negative feedback. The feedback factor
is determined by the ratio of R513 to R514. The
open loop gain of the meter amplifier (Q501 A/B,

Q502 and Q503) is sufficiently high so that the
closed loop gain is essentially a function of the

feedback factor and is, therefore, less dependent
upon the normal aging effects on the tubes and
transistors in the circuit.

4-31. The negative-going signal from Q502 is also
applied to the meter M501 for output indication.
The meter is protected against overload by the
breakdown diode CR501. If the internal ALC
switch, S601, is on, the negative-going output is
applied to the base of the differential amplifier,

Q601, causing a decrease in conduction. The

collector of Q601 will go more positive, causing an
increase in conduction of the emitter followers,

Q603 and Q604. This causes the emitter of Q604
to also become more positive. The positive-going
signal is applied to the bases of Q605 and Q606
increasing their conduction and causing both col­lectors to become more negative.

4-35. External Leveling

4-36. A simplified diagram of the ALC circuit is
shown in Figure 4-8. Operation of the external
leveling is the same as that described for internal
leveling with two exceptions. Operation of the

ALC circuit is such that the ALC attenuator (part

of the PIN diode modulator) will no longer be part
of the circuit; therefore, since the ALC attenuator
is removed from the overall circuit, the meter,

M501, will indicate a RF power level but not an

accurate measure of CAL RF OUTPUT power.

4-37. Regulated Power Supply

4-38. There are three regulated power supplies:
high voltage,

supplies are series-regulated types. The series regu-

lator is connected in series with the main load. The

output voltage is monitored and compared to a
reference voltage.

applied through a control amplifier to the series

regulator. This differential voltage changes the

effective resistance of the series regulator which in

turn holds the output voltage constant (see Figure

4-9).

+20 volts, and filament. All three

The voltage differential is

4-32. The collectors of Q605 and Q606 appear as

constant current sources, so the decrease in collec­tor potential causes current to be drawn from the
PIN diodes. This increased bias current (increased
forward bias) reduces the RF power output to its
original level.
Q605 is delivered to the RF PIN diode attenuator
allowing less RF to pass through it also. The net
result is that an increase in klystron output causes

an increase of forward bias on the PIN diodes
which decreases the RF output.

4-33. Leveling Accuracy. For accurate leveling,
the ALC and RF pin diode attenuators must track
together as far as attenuation and frequency are

concerned. The adjustment of R614, R620, and
R621 provide for matching the attenuator charac-

teristics.
4-34. ALC Cal Output. The RF OUTPUT can be

controlled by adjusting the front panel ALC CAL
OUTPUT control which varies the bias on the base
of the differential amplifier, Q602, which in turn
changes the bias on the PIN diode attenuator.

The negative-going output from

Figure 4-9. Series-Regulated Power Supply

4-39. The high-voltage supply consists of two sup­plies which have been combined to obtain required
voltages. They are a —320 volt supply on which a

–350 volt supply has been stacked to provide a

total of -670 volts. Both supplies use voltage
doublers to drive series regulator circuits. Since this

is a combined circuit arrangement, the —320 volt

and —400 volt supplies are interdependent. There
is also a gas regulator tube, V105, connected to the
– 320 volt supply to provide a –212 volt regulated
source.

4-40. There are two low-voltage supplies. One
provides +20 volts DC for the ALC circuit, the

4-6

TM 11-6625-2820-14&P

other 6.1 volts DC for filament operation. The +20

volt supply uses a voltage doubler and series

regulator, while the filament supply uses a half­wave rectifier and a series regulator.

4-7/4-8

SECTION V

MAINTENANCE

TM 11-6625-2820-14&P

5-1. INTRODUCTION

5-2. This section provides maintenance and service
information for the Model 8616A. Included in this
section is a performance check which may be used
to verify instrument operation (see Appendix II).

5-3. TEST INSTRUMENTS REQUIRED

5-4. Table 5-1 lists test equipment required for the
maintenance procedures discussed in this section.
Instruments other than those recommended may
be used, provided performance meets the basic

requirements given in Table 5-1.

5-5. PERIODIC MAINTENANCE
5-6. Cleaning the Air Filter

5-7. Inspect the air filter regularly and clean it

before it becomes dirty enough to restrict air flow.

Remove filter from instrument rear and

a.

wash it in warm water and detergent.

b. Dry filter thoroughly and

instrument.

5-8. GeneraI Maintenance
5-9. Other than periodic cleaning of

as mentioned above, the Model 8616A requires no
special preventive maintenance. We do suggest,
however, that every six months or so low pressure
air be used to blow any accumulated dust out of
the instrument.

5-10. Cover Removal

5-11. The Model 8616A is equipped with remov-

able top and bottom covers. The top cover exposes
wiring harnesses and the wired side of the power­supply circuit board.
hinged and may be opened out from the instru­ment when the top cover is removed. When the
power-supply circuit board is opened out from the
instrument, all of the adjustments and tests points
are accessible. The bottom cover exposes resistor
R613 and the wired side of the ALC circuit board.

The power-supply board is

remount on

the air filters

a.

Remove the four flathead screws from

cover.

b. Slide cover back and off instrument.

5-12. TROUBLESHOOTING

5-13. The following troubleshooting procedure
isolates the trouble to a stage. The procedure
should be performed generally in the sequence
given below.

When using an ohmmeter to measure
transistor forward and reverse resistance,
quite a bit of care must be used as almost
every ohmmeter has a few ranges that
supply enough current or voltage to dam­age a transistor. Before using any ohm­meter, measure the open-circuit voltage
(open-circuit voltage of each range should
not exceed 1.5 volts), and measure the
short-circuit current (current of each
range should not exceed 3 mA). If the
open-circuit voltage and or short-circuit

current exceeds 1.5 volts or 3 mA, respec­tively ON THE OHMMENTER RANGE
THAT YOU INTEND TO USE then the
ohmmeter will probably damage the tran­sistor to be tested. For example: a DC
Multimeter cannot be used on the Rxl
and Rx10 range, but all other ranges are
perfectly safe.

POWER SUPPLIES. The high-voItage

a.

supply consists of two supplies which have been
combined to obtain the required voltages. They are
a —320 volt supply on which a —400 volt supply
has been stacked to provide a total high voltage
output of —720 volts. Both supplies use voltage
doublers to drive the regulator circuits. There is
also a gas regulator tube connected to the —320
volt supply to provide a —2.1 volt regulated source.
There are two low-voltage supplies. One provides
+20 volts DC for the ALC circuit, the other

provides 6.1 volts DC for filament operation. The
+20 volt supply uses voltage doublers; the 6.1 volt

supply uses half-wave rectifier and transistorized
series regulator circuits.

5-1

TM 11-6625-2820-14&P

Table 5-1. Test Equipment Required

5-2

TM 11-6625-2820-14&P

(1) LEVEL OUTPUT CHECK

“SOME OF THE MAINTENANCE AND
SERVICING OPERATIONS DESCRIBED

HEREIN ARE PERFORMED WITH
POWER SUPPLIED TO THE INSTRU­MENT WHILE COVERS ARE RE-

MOVED.

PERFORMING THESE OPERATIONS.

LINE VOLTAGE IS ALWAYS PRESENT

ON TERMINALS INCLUDING THE

POWER INPUT CONNECTOR, FUSE

HOLDER, POWER SWITCH, ETC. IN

ADDITION, WHEN THE INSTRUMENT

IS ON, ENERGY AVAILABLE AT

MANY POINTS MAY RESULT IN PER-

SONAL INJURY OR DEATH WHEN
CONTACTED.”

Remove four #6 x 32 screws from top

(1)

cover and remove top cover.
Open out power-supply board by re-

(2)

moving two screws that secure board to
leveler assembly.

Connect ac power line to an ac power

(3)

source. Set slide switch at 115 volts ac or
230 volts ac as appropriate.

(4)

Connect a digital voltmeter in parallel and
make the proper measurements (see Table
5-3).

Use grounded meter for filament and
—400 volt measurement.

BE CAREFUL WHEN

(a) Set up Model 8616A as follows:

LINE . . . . . . . . . .

RF . . . . . . . . . . . depressed

ALC not depressed

ATTENUATION “ : : . . . . . 012

FREQUENCY . . . . . 1800 MHz

(b) Using a

measure voltage
Q501A (easiest access is rear
panel REMOTE LEVELING IN­PUT connector). Specification:
reading should equal 120 ± 2
mV. If voltage is not within
specification refer to paragraph

5-29 and adjust.

(c) With Model 8616A as in step a,

depress ALC button and set dBm
meter with ALC CAL OUTPUT
adjust to 0 dBm. Using dc milli­volt meter measure voltage on
base of Q501A. Specification:
voltage should be approximately

100 mV.

(d) Set up power meter combination

for operation on the 3 mW range.

(e) Using power meter measure the

CAL RF OUTPUT of the Model
8616A across the entire fre-

quency range. Specification:

Level output should be constant
within ± 1.0 dB.

dc millivolt meter

depressed

on base of

b. TROUBLESHOOTING LOCATION

CHART. Check instrument trouble symptoms
against those listed in Table 5-2, Trouble Location.

ISOLATING TROUBLE TO A SPECIFIC

c.

CIRCUIT. Because each mode of operation uses
different circuit combinations (see Figure 5-1),
trouble can be isolated to a specific circuit by
checking the operation of each mode of operation

in logical order.

ISOLATING TROUBLE TO THE PIN

d.

MODULATOR. This procedure isolates trouble to
the PIN diode modulator box or to the instrument
circuitry.

(f) If level output is not within

specification refer to paragraph

5-28 and check and if necessary
adjust klystron repeller voltages
across frequency band.

(g) AIso, refer to paragraph 5-33 and

check and if necessary adjust the
ALC Amplifier for proper opera-

tion.

(h) Recheck signal generator leveled

output. If level output is still not
within
Table 5-2 eliminate cause of

specification refer to

5-3

TM 11-6625-2820-14&P

5-4

Figure 5-1. Model 8616A Block Diagram

Table 5-2. Trouble Location

TM 11-6625-2820-14&P

Table 5-3. Power Supply Adjust

5-5

TM 11-6625-2820-14&P

trouble to either the PIN diode
modulator box or instrument cir­cuitry.

(2) ON-OFF RATIO CHECK. Refer to

paragraph 5-42.

5-14. REPAIR

5-15. The etched circuit boards used in the 8616A
are of the plated-through type and consist of a base
board and conductor. The board does not include
funneled eyelets. The conductor material is plated
to the wall of the holes and thus the conductor is
effectively extended through the hole. This type of
board can be soldered from either the conductor or
component side of the board with equally good
results. The rules given below should be followed
when repairing a plated-through type etched circuit
board .

Avoid applying excessive heat when sol-

dering on the circuit board.

b. To remove a damaged component, clip
component leads near the component, then apply
heat, and remove the leads with a straight upward
motion.

outer truarc ring from the outer cover of the
klystron cavity (see Figure 5-2).

d. Remove outer cover. Remove inner truarc
ring holding klystron clamp housing in klystron
cavity.

Pull tube socket from klystron with a

e.
straight pull. Grasp klystron tube and remove from
cavity.

f.

Unscrew clamp nut, lift out clamp spacer,

and remove klystron (see Figure 5-2).

Remove waffle washer from cavity.

g

NOTE

Refer to paragraph 1-13

rant y claim instructions.

5-18. Tube Replacement

a. Reassemble new klystron, housing, spacer,

and nut.

b. Set klystron frequency drive at top end

(high frequency dial setting) for klystron centering.

for klystron war-

c. Use a special soldering iron tip to remove
components having multiple connections, such as
potentiometers, transformers, etc. Refer to Table
5-1 for type of soldering tip required.

d. Use a toothpick to free hole of solder
before installing a new component.

5-16. KLYSTRON REMOVAL AND REPLACE–

MENT

5-17. Tube Removal

BEFORE ATTEMPTING KLYSTRON

REMOVAL OR REPLACEMENT, BE
CERTAIN THAT LINE POWER IS COM­PLETELY REMOVED FROM INSTRU­MENT.

a. Remove panel cover on left (with

respect to front panel) side of instrument
(see Figure 5-2).

Set klystron frequency drive at top end

(4500 MHz frequency dial setting).

c. Using truarc pliers which are available in a

repair kit, HP Part No. 08614-800, remove the

Place waffle washer in klystron cavity.

c.

d. Insert klystron into klystron cavity.

Klystron should be inserted straight into
cavity. Insertion of klystron should re­quire no unnecessary force; the klystron
should fit snugly but easily, into cavity.

Replace inner truarc ring on clamp hous-

e.
ing (if the klystron is properly in place the ring will
fit properly). Allow tube to be centered by center
conductor.

Install tube socket and outer cover.

f.

Place edge of truarc ring on outer cover

g.

and rotate until ring lies flat on cover and is easily
accessible with truarc pliers.

Refer to Calibration Checks (paragraph

h.

5-26) and make necessary adjustments.

5-19. RF PROBE REMOVAL AND REPLACE-

MENT

5-20. Probe Assembly Removal

5-6

TM 11-6625-2820-14&P

Figure 5-2. Cut-A way View of Klystron Cavity and Klystron Assembly

BEFORE
ASSEMBLY REMOVAL OR REPLACE­MENT,
POWER IS COMPLETELY REMOVED

FROM INSTRUMENT.

Remove top cover from instrument.

a.

b. Set FREQUENCY (MHz) drive to the

highest frequency setting (4500 MHz).

c.

Remove Attenuator access cover from
Klystron Cavity Casting and disconnect
assembly connectors from instrument.

d. Remove the cable assembly connector
from the defective RF probe cable. Be careful not
to lose any connector parts as they will be required
for reassembly.

Remove

e.

guide.

ATTEMPTING

BE CERTAIN THAT LINE

the probe cable from the cable

PROBE

cable

Remove the retaining screw holding the

f.
tuning carriage and remove the probe from the
casting.

The defective probe assembly should be

g.

returned to your local Hewlett-Packard Sales and

Service Office for repair or replacement (see list at

rear of manual).

5-21. Probe Replacement

THE

SHOULD BE HANDLED WITH CARE.

THE PROBLE SHOULD BE PLACED IN

A PROTECTIVE SHIELD WHEN HAND­LING OR SHIPPING.

a.

insert the new probe into the Klystron Cavity
Casting and replace the probe retaining screw.

PROBE IS

To install a new probe assembly, carefully

FRAGILE AND

5-7

TM

11-6625-2820-14&P

CARE MUST BE TAKEN NOT TO
DAMAGE THE RESISTIVE ELEMENT
ON THE PROBE END OR THE SPRING
WIPERS THAT MAKE CONTACT WITH
THE PROBE GUIDE TUBE.

f.

Trim the dielectric flush with the end of
the clamping body so that the center conductor is
bare.

Trim the center conductor protruding

g.

from the clamping body, then place the insulator
washer on the center conductor.

b. Insert the probe assembly through the

cable guide. Install the cable guide.

c.

Trim the insulation from the end of the
problem assembly cable (for RF UNCAL probe, 5/16
inch; for RF CAL and ALC probes, 1/4 inch).

d. Place cable assembly connector parts on
cable, with the exception of the clamping body,
and fold the braid upon the connector assembly

(see Figure 5-3).

Place the clamping body on the RF UN-

e.
CAL cable and screw the clamp nut and clamping
body together.

NOTE

After tinning center conductor the diame­ter may be too large to fit into the pin,
making it necessary to file the center
conductor to the proper diameter.

h. In preparing the ALC and CAL RF

probes, cut the inner conductor insulation about

1/8” from folded braid.

i.

Flatten inner conductor to approximately

1/8” wide and 1/32” thick.

Tin flattened conductor with solder and

j.

allow it to wick slightly.

5-8

Figure 5-3. RF Probe Assembly

TM 11-6625-2820-14&P

k. Press end of inner conductor with
ensure good contact and smooth insertion
Cal.

Before connecting connector assembly in-

1.
to the instrument, connect an ohmmeter between
the probe center

measure the resistance across the range of the
attenuator. The resistance should be approximately
50 ohms ±5 ohms. If the probe is open or shorted
at any point, the probe is defective and should be
replaced.

m. Replace the connector assembly as it was

before disassembly. Connect the probe connector
to the instrument, making certain the center con­ductor makes good contact.

The probe installation is complete. Reas-

n.
sembly the instrument except for the front, right
side panel, which is removed when performing the

output power calibration adjustments.

5-22. PIN MODULATOR REMOVAL AND RE-

PLACEMENT

5-23. Modulator Removal

5-24. The PIN modulator CANNOT be repaired in

the field. If the PIN modulator is found to be
faulty, it should be returned for repair. Remove
the four screws holding the PIN modulator only.

Removal of screws holding the PIN diodes in place

can cause contamination of the PIN diodes, high

SWR, etc.

a. Remove power line from instrument.

b.

Remove top and bottom covers.

conductor and ground and

a file to

recepti-

f. (Referring to Figure 5-14 and paragraph

5-54) replace crystal diode body.

Disconnect ALC Bias Feed connections (1

g.

and 2 on A500 board) from ALC circuit board.

h. Remove three screws holding PIN modula-

tor in place.

i.

Remove PIN modulator from instrument.
Carefully pack PIN modulator in a con-

tainer and return to your local Hewlett-Packard

field office for repair or replacement.

5-25. Modulator Replacement

Replace three screws that hold PIN mod-

a.

ulator to instrument chassis.

b. Connect RF OUTPUT cable to J701.

Connect ALC Bias Feed connections to

ALC circuit board (A500).

d. Connect cable assembly connectors to

PIN diode modulator. (See CAUTION, paragraph

5-24).

e.

Place crystal diode into modulator; the
dark-coated side of crystal fits into the finger of
center conductor. WHEN INSTALLING CRY-

STAL, DO NOT FORCE TIP OF CRYSTAL INTO
CENTER CONDUCTOR AS FINGERS IN
MOUNT MAY BE DAMAGED OR BENT. Bending
or damaging center conductor fingers will cause
sporadic operation of the diode.

c. Place instrument on its side.

DO NOT HANDLE CRYSTAL DIODE,
CR701 NEEDLESSLY. A static charge

which builds up on a person, especially on

a cold, dry day must NEVER, be allowed
to discharge through element. When in­stalling always touch casting first to insure
no difference in potential between hand
and casting.

d. (Referring to Figure 5-19 and paragraph

5-54) disconnect crystal diode, CR701, and crystal

diode body, P706, from PIN modulator.

e.

Disconnect cable assembly connectors
from the modulator (see Figure 5-3). Be careful
not to lose any disassembled parts as they will be
required for reassembly.

f. (Referring to Figure 5-14 and paragraph

5-54) replace crystal diode body.

5-26. CALIBRATION

5-27. Regulated Power-Supply Adjustment

Remove instrument top cover and open

out top circuit board (see paragraph 5-10).

b. Depress LINE button.

c.

Connect ac power line to an ac power
source. Set ac voltage at 115 or 230 volts as
appropriate.

d. Connect DC voltmeter digital and vacuum

tube voltmeter in parallel and make necessary

adjustments (see Table 5-3).

5-9

TM 11-6625-2820-14&P

Use ungrounded meter for filament and

--400V measurement.

Figure 5-4. PIN Modulator (External View)

5-28. Frequency Tracking, Preliminary

tors; a fuse holder, and a power cord. Connected as
shown, this modulator provides a power line freq­uency modulation voltage continuously variable in
amplitude from 300 volts peak-to-peak, with phase
variable over a range of approximately 80 degrees,
plus a 6.3-volt AC output for oscilloscope sweep
control.

d. Apply external FM (60 cycles) and view
mode patterns on oscilloscope. Adjust PHASE
control of FM modulator and adjust tracking pot
(R219) for mode pattern shown in Figure 5-5.

e.

With Frequency Tracking adjustment
completed, measure klystron beam current: Using
a clip-on milliammeter, connected to wire on cen­ter feedthrough capacitor (C4), current must not
exceed 30 mA.

5-29.

Power Adjustment

a. Connect dc digital voltmeter between the
klystron repeller white/purple/yellow wire coming
from center conductor support rod past relay
switch between PIN DIODE BOX and Klystron
Cavity Casting and ground. Make sure F control
on front panel is set at zero (center of pot range),
and proceed as indicated in Table 5-4.

Table 5-4. Klystron Repeller Voltages

b. At a dial frequency of 1800 MHz set
ATTENUATOR dial for a calibrated output of
about 0 dBm.

c. To observe repeller modes of the klystron,
a FM Modulator, with adjustable phase and ampli­tude controls, is necessary. Such a device is shown
in Figure 5-5; it consists of a small power trans­former connected with the primary and secondary
windings interchanged; two one-megohm poten­tiometers; a 0.01 µF capacitor; two BNC connec-

5-30. RF Power Output Adjustment.

Front Panel Settings: Have ALC button
released (OFF). Set ATTENUATION (dB) to 0.12
dB. Set FREQUENCY to 1800 MHz.

b. CAL RF Adjustment:

(1)

With a power meter, measure the
CAL RF output power. It should be
–11 dBm ±0.1 dBm.

If it is not, loosen the two set screws

(2)

in the attenuator drive shaft bevel
gear with your fingers until the out­put power is –11 dBm. Without dis­turbing the –11 dBm power setting,
turn the attenuator knob on the front
panel until the attenuator counter
reads 012 dB. Tighten the two set
screws in the bevel gear.

c. UNCAL RF Adjustment:

(1) Measure the UNCAL RF power out-

put. It should be –3 dBm ±0.3 dBm.

(2) If it does not, the RF UNCAL probe

requires adjustment. The front, right

panel should be removed, exposing

the probe assembly cable guide.

Remove the screw in the cable guide
that is in line with the UNCAL probe
retaining screw (see Figure 5-11).

Insert a long Allen wrench through
the hole left by removing the cable
guide screw into the UNCAL probe
retaining screw.
screw to adjust the UNCAL probe

Turn the retaining

5-10

TM 11-6625-2820-14&P

Figure 5-5. Frequency Tracking Setup

5-11

TM 11-6625-2820-14&P

penetration for –3 dBm ±0.3 dBm
output.

d. ALC Adjustment:

(1) With a dc voltmeter (HP Model

412A) measure the dc voltage at the
output of the CR701 crystal diode, or
the base of Q501A.

DO NOT USE A DIGITAL VOLTMETER
WITH AUTO-RANGING AS IT MIGHT
DAMAGE THE CRYSTAL DIODE.

(2)

The dc voltage should be 120 mV ±2
mV.

(3)

If it is not, the ALC attenuator probe
requires adjustment. The front, right
side panel should be removed, expos­ing the probe assembly cable guide.

Remove the screw in the cable guide

that is in line with the ALC probe
retaining screw (see Figure 5-13). In­sert a long Allen wrench through the
hole left by removing the cable guide
screw into the ALC probe retaining
screw. Turn the retaining screw to
adjust the ALC probe penetration for

120 mV ±2 mV at the ALC crystal
output .

5-32. Frequency Tracking

a.

Use a frequency
actual frequency at ‘dial settings of 1800 and 4500
MHz. To eliminate backlash error, always approach
frequency settings in the same direction.

b. The difference in frequency meter read­ings for Model 8616A dial settings should be 2700
MHz.

c. Refer to graph, Figure 5-6. The horizontal

axis represents the measured frequency change

from step b, the vertical axis indicates the dial

corrective setting. For example, if the difference
between dial settings (step b) is 2177 MHz, the
corrective setting for the dial as found on the graph
is 1805 MHz. To make the corrective setting, set
the frequency dial to 1800 MHz, loosen the two
setscrews that clamp the dial plunger to the rack,
shift the dial to 1805 MHz, and then tighten the
two setscrews.

d. If any plunger adjustment was necessary

(step c), repeat Frequency Tracking, Preliminary

Adjustments (paragraph 5-28). Repeat this pro-

cedure until rotation from low to high frequency
corresponds to a change of 2700 MHz ±6 MHz.

e.

Set actual frequency to 1800 MHz.

Loosen spur gear on counter shaft and rotate gear

until frequency dial reads approximately 1801.5
MHz.

Final

meter to measure the

5-31. Meter Amplifier

Turn off RF power. Zero front panel

meter with front panel ZERO SET.

b. Depress RF button and measure meter
amplifier output voltage (junction of R515 and
C502). This voltage must be -6.4 ±0.3V at 1800
MHz. This corresponds to a gain of 53 ±2.

Front panel meter should read ±1.2 ±0.2

dBm.

Table 5-5. Klystron Probe Adjust

5-12

f.

Check FREQUENCY (MHz) dial settings
at both upper and lower ends of dial travel. The
respective dial end points should be less than 1800
MHz and greater than 4500 MHz. If dial travel is
not satisfactory then loosen bevel gear on fre­quency drive shaft and reset dial.

Check microswitch action: The micro-

g.

switch
(2988
switch
switch
should

should energize and de-energize at about

to 3012 MHz). If microswitch does not

at the proper dial settings then the micro­cam (located on underside of cavity casting)
be repositioned.

Figure 5-6. Frequency Trucking

h. Being careful to approach all dial settings

from the same (either clockwise or counterclock-

wise) direction, using the procedure given in para-

graph 5-38, check the accuracy of the frequency
dial by approaching all dial settings from a clock-

wise direction and then from a
direction.

NOTE

The Frequency Meter used
brated to an accuracy of approximately

counterclockwise

must be cali-

(±0.07%).

If frequency dial reading errors are greater

i.
than ±10 MHz then shifting the dial may bring all
errors within specification. If shifting dial will not

sufficiently correct errors then it may be necessary
to shift the position of center conductor support
rod (see Figure 5-11). The center is held in place
by a notched captive screw at the end closest to

the right side of the instrument which must be

loosen to allow center conductor adjustment “in”

“out”

or
center conductor rod so that original position may
always be known.
positive, adjust center conductor toward right side

of instrument. When adjusting center conductor
position never
thousandths of an inch at a time.

of the klystron cavity. Notch or scratch

If overall frequency dial was

change by more than about 20

TM 11-6625-2820-14&P

If any adjustment of instrument was nec-

j.

essary
procedure until no adjustment is required.

5-33. ALC Amplifier

and ATTENUATION (dB) Of 012.

dBm meter to 0 dBm by means of ALC CAL

OUTPUT knob.

PUT and adjust as indicated in Table 5-6;

power meter and a thermistor mount.

repeat

Set FREQUENCY (MHz) to 1800 MHz

Depress ALC button and set front panel

b.

Track ALC amplifier at CAL RF OUT-

entire

Table 5-6. ALC Amplifier Adjust

check and adjustment

use a

NOTE

A dial reading of 1800.5 MHz when the
actual frequency was 1800 MHz is a posi­tive error.

5-13

TM 11-6625-2820-14&P

5-34. Pulse Modulation Adjust

a.

externally-generated 20V, 3 µsec positive pulse to
the front panel pulse BNC input.

sufficient to completely pulse modulate the CAL
RF output power. This condition is achieved when
the ON side of the detected pulse begins to exhibit
a flatness.

5-35. Square-Wave Adjust

detected square wave output from CAL RF OUT­PUT on an oscilloscope.

±50 Hz,

5-35A. AM Adjust

graph 5-45).

change value of C404 by approximately 10 pF and
recheck operation.

Depress PULSE button and apply an

b. Adjust R404 so that the input pulse is just

a.

Depress SQ WAVE button and display

b. Adjust R410 for best symmetry at 1000

NOTE

The value of C402 may be 2250 pF, 2676
pF, or 3000 pF depending upon which

value will give the instrument square wave

frequent y range needed.

a.

Check AM operation at 50 Hz (see para-

b. If AM waveform is not satisfactory,

NOTE

5-36. PERFORMANCE CHECKS

5-37. The performance check procedures are used
to check the instrument against its specifications.
All checks are made from the front panel, thus the
instrument panels need not be removed. The pro­cedure is useful in incoming or outgoing quality

control check, periodic maintenance, or after­repair check.
paragraphs 5-38 and 5-46.

5-38. Frequency Range and Accuracy

a.

5-7.

b. Set up Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . . . . . . . .

c.

an 1800 MHz dial indication on the Model 8616A.

d. Set frequency meter to approximately

1800 MHz and note actual signal frequency.

e.

to a frequency dial indication of 4500 MHz.

be 1800 to 4500 MHz, accuracy of dial indication
should be ±10 MHz.

Repeat above procedure every 100 MHz

f.

Frequency range of Model 8616A should

Performance checks are given in

Connect instrument as shown in Figure

depressed
depressed

Set power meter for a mid-scale reading at

Typically, undistorted AM operation is
achieved with either a 30 or a 39-pF
capacitor.

Figure 5-7. Frequency and Power Measurement

5-14

5-39. F Control Check

a. Connect instrument as shown in Figure 5-7.

TM 11-6625-2820-14&P

b. Setup Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . . . . depressed

RF . . . . . . . . . . . . . . . . . . . . . . depressed

FREQUENCY . . .

Set power meter for amid-scale reading.

c.

d. Turn F control fully counterclockwise
and measure output frequency with power meter
and frequency meter.

e. Turn F control fully clockwise and
measure output frequency.

f. The difference between the readings, steps

d and e, should be approximately 1.5 MHz.

5-40. Power Output Check

a. Connect instruments as shown in Figure

5-7, omitting the frequency meter.

b. Set up Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . .

FREQUENCY . . .

ALA . . . . . . . . . . . . . . . . .

Power output at UNCAL RF OUTPUT

c.

should be at least 0.5 mW.

d. Maximum power output at CAL RF OUT-

PUT should be at least 2 mW.

5-41. Leveled Output Check

a. Connect instruments as shown in Figure
5-7, omitting the frequency meter.

Set up Model 8616A as follows:

b.

frequencies of interest

. . depressed
. . depressed

frequencies of interest

not depressed

d. Noting power meter variation from setting

(step c), tune Model 8616A across frequency band.

The variation should not exceed ± 1.0 dB.

5-42.

Pin Diode On-Off Ratio

a. Connect instruments as shown in Figure

5-7, omitting the frequency meter.

b. Set up Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . . . .

FREQUENCY . . . . . . . . . mid-frequency

EXTERNAL PULSE . . . .

ATTENUATION . . . . . . . . . . . ..+9 dB

ALA . . . . . . . . . . . . . . . . .

c. Set power meter on +10 dBm scale and
adjust Model 8616A ATTENUATION control for
convenient reference.

d. Depress EXTERNAL PULSE on Model
8616A.

e. Reference on the power meter should
change to the
off ratio must be at least 20 dB.

f. If the on-off ratio is not 20 dB or greater,

the PIN modulator may be defective. Check bias
current through R414 and R420: the current
through R414 should be approximately 6 mA, and
the current through R420 should be 3 mA. If these
bias currents are correct, the modulator is defective

(refer to paragraph 5-22) or CR403 shorted.

543. Internal Square-Wave Check

a.

5-8.

–10 dBm scale. Specification: On-

Connect instruments as shown in Figure

. . depressed

depressed
not depressed
not depressed

LINE . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . .

FREQUENCY . . . . . . . . . . ..1800 MHz

ALA . . . . . . . . . . . . . . . . . . . .

ALC CAL OUTPUT . . . counterclockwise

NOTE

Before ALC button is depressed, dBm

meter should indicate approximately +1
dBm; depressing ALC button should cause
d13m meter indication to decrease. ALC
CAL OUTPUT: 0 dBm (dBm meter indi­cation); ATTENUATOR (dB): --0 dB or
less.
c. Set power meter for convenient mid-scale

reading.

. . depressed
. . depressed

. depressed

b. Set up Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . . . .

INTERNAL SQ WAVE . . . . . . depressed

ATTENUATION . . . . . . . . . . . . . .0 dB

SQ WAVE . . . . .

c.

Set oscilloscope sweep time to .1

MHz/cm.

d. Readjust rate control to display one com­plete square wave on oscilloscope. Square wave
symmetry should be better than 45/55%. Range
should be 950 to 1050 Hz.

fully counterclockwise

depressed
depressed

5-15

TM 11-6625-2820-14&P

Figure 5-8. Internal Square Wave Check

5-16

Figure 5-9. External Pulse Check

TM 11-6625-2820-14&P

544. External Pulse Check

Connect instruments as shown in Figure

a.

5-9.

b. Setup Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . . . .

RF......................

EXTERNAL PULSE . . . . . .

Set up pulse generator for a 20-volt 50 prf

c.

depressed
depressed

depressed

signal with a pulse width of 3 µsec.

d. A pulse presentation should be seen on

the oscilloscope. Specification rise time: 2 µsec max.

e.

Set up pulse generator for a 20-volt

5000-prf signal with a pulse width of 3 µsec.

A pulse presentation should be seen on

f.

the oscilloscope. Specification rise time: 2

µsecmax.

545. External AM Check

Connect instruments as shown in Figure

5-10.

b. Setup Model 8616A as follows:

LINE . . . . . . . . . . . . . . . . . . . .

RF......................

EXTERNAL AM . . . . . . . . . . .

ALC. . . . . . . . . . . . . . . . ....

depressed
depressed

depressed
depressed

ALC CAL OUTPUT –3 dBm (dBm meter)

FREQUENCY . . . . . . . . . . ..1800 MHz

ATTENUATION . . . . . . . . . 0 dB or less

Apply a 6 *0.1 volt peak-to-peak l-kHz

c.

sine wave to front panel BNC input.

d. Using ALC CAL OUTPUT to vary DC

level of detected sinusoid, center wave so there is
no peak clippings (vary input amplitude, if neces-

sary).

Figure 5-10. External AM Check

Change 2

5-17

TM 11-6625-2820-14&P

e.

Adjust vertical sensitivity of the oscillo­scope to give
detected 1 kHz signal

a 6-cm vertical display of the

and then increase signal

frequency to 1 MHz. The vertical display of the 1
MHz signal should be greater than 3.0 cm.

546. MEASUREMENT OF RESIDUAL AND IN-

CIDENTAL FM

a. Connect instruments as shown in Figure

5-12, without the test oscillator in the setup.

b. Setup Model 8616A as follows:

d. Roll of masking tape (1/2-inch or 1-inch,

width).

e.

Rubber cement.

549.

Procedure

5-50. If it is necessary to replace the cam cable,
order it by HP Stock No. 08614-299 and descrip

tion

of usage. For easier access to the cams, remove

the screws holding the High Voltage circuit board

and swing the board out of the way. Use Figures
5-11 and 5-13 as a guide and proceed as follows:

LINE . . . . . . . . . . . . . . . . . .

RF . . . . . . . . . . . . . . . . . . . .

. . depressed
. . depressed

FREQUENCY . . . . . . . . . . . . . 2.5GHz

c.

Adjust frequency meter output for 10

kHz/V. Line sync oscilloscope.

d. Adjust transfer oscillator for 125 MHz

and Harmonic of 200.

e.

Adjust frequency for 10 kHz difference

frequency reading on frequency meter.

f. Residual FM (line related components)

reading (“peak to trough”) on oscilloscope is less
than 250 mV peak (250 mV = 2500 Hz).

Set up Model 8616A as follows:

g.

INTERNAL SQ WAVE . . . . . . depressed

ATTENUATION . . . . . . . . . . . .–10dB

h. Incidental FM is negligible.

i.

Connect instruments as shown in Figure

5-12, with the test oscillator in the setup.

Set up Model 8616A as follows:

j.

a.

Remove power cord from instrument.

b. Remove instrument top cover and atten-

uator access cover.

c.

Turn FREQUENCY (MHz) to approxi-

mately the middle

d. Orient Length Cam to Frequency Cam as

of the frequency band.

shown in Figure 5-11.

e.

Using a lead pencil, mark the position of
each cam and the end of the threaded portion of
the center conductor support rod on the klystron
cavity casing.

f.

Using the hex socket wrench and a 3/8­inch open-end wrench, remove both terminal
screws,

the four washers, and the two nuts
(10-32x0.375; hex nuts).

Remove both terminal screws horn cable.

g.

h. On replacement cable, place a mark half-

way between each end. Using matches apply heat
to an area approximately 1/2 to 3/4-inch on either
side of the mark to remove wire tension (heat to
nearly white hotness.

EXTERNAL FM . . . . . . . . . .

. depressed

i.

Cut 10 or 11 strips of masking tape,
approximate y 1-inch in length.

k. Adjust test oscillator for a 10 kHz, 5 to 6

volt peak modulating signal.

j.

Remove 3 retaining screws from Fre­quency Cam and remove cam from instrument

1.

Incidental FM is negligible.

5-47. CAM CABLE REPLACEMENT k. Slide cable through one terminal screw so

(Note: 3 retaining screws are 4-40x0.625, FH).

that cable is secured to terminal screw as shown in

5-48. Tools Required

Figure 5-13, for the Frequency Cam, and install
terminal screws on Frequency Cam.

a.

Open-end wrench (3/8-inch).

b. Hex-socket wrench and 3/8-inch socket or

equivalent tool.

Be careful not to catch cable between

c.

Book of matches.

5-18

lockwasher and cam.

PIN : 032939-002

TM 11-6625-2820-14&P

Figure 5-11. Top View, Cover Removed

5-19

TM 11-6625-2820-14&P

Figure 5-12. Residual and Incidental FMCheck

Figure 5-13. Exploded View – Cam Assembly

TM 11-6625-2820-14&P

m. Slide cable onto cam just past point A and
B; the other half should pass over points C, D, and
E).

NOTE

Each cam as shown in Figure 5-13 has two

lips along which the cable should travel,
one cable must travel along the upper lip,
of both cams and one cable must travel
along the lower lip of both cams.

n.

Slide other half portion of cable onto cam

just past point D and tape to cam.

Place Frequency Cam in original position

o.

in instrument and replace retaining screws.

Turn Length Cam so that cams are not

p.

touching at point F and place cable between cams:
on cable along upper lip of cam and the other
along lower lip of lip of cam.

Turn Length Cam so that it is apparently

q.

touching Frequency Cam at point F and place two
pieces of masking tape across the two cams at
point F.

step e, the other marks made should match
appropriately.

w. Perform Frequency Tracking adjustments,

paragraph

5-28 and 5-32.

5-51. LOW PASS FILTER REPLACEMENT

5-52. Took Required

Low heat soldering iron and solder (flux)

a.

b. Small pair needle nose pliers.

c.

Small pair pliers.

5-53. Procedure

5-54. Figure 5-14 illustrates Low Pass Filter and
ALC crystal diode (CR701) parts with stock num­bers. The illustration is an assembly drawing. Part

removal is the reverse of illustrated assembly in-

structions. The first step for disassembly is to
unsolder the cable to low pass filter and grounding
lug connections. The last step of assembly is to
solder the cable to Low Pass Filter and grounding
lug connections.

r.

With the cams held together, slide the
cable which passes over points C and D past point
E and the cable which passes over point A past
point B and tape each portion of cable to the cam.

NOTE

It is important that each cable portion
have as little slack between it and the
cams as possible: a loose cable causes
backlash.

s.

Slide cable ends through second terminal
screw so that cable is secured to terminal screws as
shown in Figure 5-13, for the Length Cam.

t. Install the second terminal screw on the

Length Cam and tighten both terminal screws to

remove all slack in cable.

u.

Remove masking tape from cams and
apply rubber cement to ends of cable to ensure
that cable will not unravel.

v. Turn FREQUENCY (MHz) knob to

match Frequency Cam to pencil mark made in step

Before touching CR701 refer to paragraph
5-24, step c – Caution.

5-55. CAVITY WIPER REPLACEMENT

5-56. The following procedure will enable you to
easily replace the wipers in the cavity of the 8616A
signal generators. These wipers may need to be
replaced when holes appear in the FM mode

pattern and the klystron is known to be good.

5-57. Parts Required

5-58. The correct parts to order are listed below:

HP Part Number

08616-210
08614-282

5-59. Replacement Procedure

1.

Set the attenuator to –20 dBm. This will

Description
Wiper, Cavity
Conductor, Center

prevent damage during the wiper replacement,

Quantity

2

1

5-21

TM 11-6625-2820-14&P

5-22

Figure 5-14. Low Pass Filter Assernbly Drawing

TM 11-6625-2820-14&P

2. Remove

bottom, and trim

3. Place instrument on left side frame and
unsolder repeller filter lead from bottom of main
deck (white, yellow, violet). There are two leads
the same color, so be sure to remove lead going to

the cavity.

4.

Remove two lower cavity retaining screws

that hold cavity halves together, and remove the

UNCAL RF probe.

5. Place instrument on right side frame;
remove klystron cover plate on left side of instru­ment, then remove klystron.

6. Place instrument on its bottom and re­move all screws and covers from right side frame
and remove the right side frame.

7. Slide off base casting plate from ends of
cavity probe guide and center conductor support
rods.

8. Remove attenuator casting cover from top
of cavity casting.

all instrument

strips.

covers, top and

shafts to the right. Place right cavity half so that

wipers are facing upward. Right cavity half and

tuning carriage may offer some resistance during

removal. A small plastic hammer may be used to

free the two cavity halves from each other.

15. Be very careful to prevent damaging

probes and remove the three screws from center

ring of wipers that hold the wipers to the tuning

carriage.

16. Using a thin bladed screwdriver between
back of outer wiper and teflon bearing plate,
remove outer wiper.
damage probes. Remove teflon bearing plate and
three metal spacers. Note the placement of the
wipers.

17. Now remove inner wiper from the support
rods and clean any excess silver paint from probe
guide tubes.

18. Inspect new wipers for bent fingers. Care­fully slide a new wiper over probe guide tubes. It

may require tapping with plastic hammer around

the wiper back plate to make wiper slide into

position.

Again be careful not to

9. Use a sharp scribe or awl and mark tuning
carriage position on its tuning rod. Also mark
position of center conductor rod at right side of
casting. Then loosen shaft clamp on center conduc­tor.

10. Tune frequency control to high frequency
stop. Use long nose pliers to grip center conductor
and slide to left out of the cavity. A new
center conductor should also be installed when
wipers are changed. Tune to the low frequency
stop and remove the frequency tuning and attenua­tor knobs.

11. On left side of instrument remove the
four screws holding cavity casting and three screws
into front panel under forward trim strip.

12. Carefully slide front panel and cavity
assembly to right until left mainframe side is
disengaged from front panel. Now slide front panel

forward until tuning and attenuation shafts are
clear. Tilt panel forward as far as possible without

breaking any leads.

13. Loosen two screws in top of tuning car­riage that hold carriage to its tuning shaft. Now
remove two screws from cavity top that hold
cavity halves together.

14, Using your right hand, gently slide the

right cavity half and tuning carriage off tuning

19. Place toothpicks in screw holes of support
rods. Slide metal spacers over toothpicks followed
by teflon bearing and outer wiper. Again, outer
wiper may require gentle tapping to seat fully into
position.

NOTE

Holes are not symmetrical in teflon bear­ing or wipers.

20. Holding the cavity upright remove one

toothpick at a time and install the wiper retaining
screws. Be careful spacer does not move when a
toothpick is removed.

21. Although not necessary, the use of a small

amount of silver paint around probe guide tubes
and the three wiper retaining screws is recom-

mended. This will help prevent RF leakage.

22. Using paper tissues, remove any excess

lubricant from inside of cavity. Use a small amount
of Moly coat on another tissue and clean inside of
cavity so that cavity walls feel lubricated, but no
grease can be seen.

23. Again, holding left cavity half in left hand

and right cavity half in right hand, slide the right
half over the tuning shafts being careful to line up
tuning carriage holes.

5-23

TM 11-6625-2820-14&P

Be very careful not to damage wiper
fingers during assembly.

24. Slide the two halves together until the
tuning carriage can be pushed far enough forward
for wipers to enter cavity. Now slowly push tuning
carriage to the left until the wipers enter the bevel
at the edge of the left cavity half. Now carefully
slide wiper into cavity body until both wipers are
fully inside cavity.

repeller filter. Insert allen wrench into the

center conductor, alongside repeller filter

lead, and use only enough pressure to
slowly slide repeller filter out of the cen­ter conductor.

30. Slide tuning carriage back to mark pre-

viously scribed on tuning shaft during disassembly,
and tighten two screws in top of tuning carriage.

31. Now follow steps 12 through 1 disas-

sembly in reverse to re-assemble the instrument.

25. Carefully slide cavity halves together and
re-install the two upper allen retaining screws into
cavity assembly.

26. Now take new center conductor and
scribe mark on shaft in approximately the same
location as previously done on the old center
conductor.

27. Use silver polish and clean outer surface
of center conductor to remove all oxidation. Using
same procedure as on cavity walls, lightly wipe on
and wipe off Moly coat lubricant.

28. Now roll center conductor along clean
bench or table to form the fingers until they are a
firm fit over klystron grid ring. (See Figure 5-15.)

32. The instrument will need to have both the

power output and frequency re-calibrated after this
procedure (refer to paragraphs 5-28 through 5-32).

5-60. Frequency Drive Gear Replacement

5-61. The frequency drive gear HP Part Number

08614-245, has been changed to an all brass gear.

The following procedure will speed up replac-

ing the gear:

1. Tune the generator to mid-band. Use a
scribe to draw a line across the tops of the two
frequency cams marking where they touch.

2. Wrap about four inches of masking tape

around the ends of each cam to hold down the
stainless steel anti-backlash wires.

3. Remove the three 4-40x.625 inch screws

holding each cam. Very carefully lift off the cams

as a unit.
cams fold over, the stainless steel wires will have to
be restrung and the job will take about three times
as long. Place cams under something heavy enough
to hold them flat while you finish replacing gear.

Do not allow the cams to fold over. If

Figure 5-15. Forming the Center

Conductor Fingers

29. Remove the repeller filter from the old

center conductor and re-install the repeller filter in

new center conductor. Now lay center conductor

assembly aside temporarily y.

NOTE

It will be necessary to use a long, ten inch

or longer, allen wrench to remove the

5-24

4. Mark on casting, position of one of screw

holes on gear.

5. Turn signal generator upside-down. Re-

move bottom cover.

6. Remove the two 6-32x3/8 inch screws

holding 2.625 inch repeller pot cover.

7. Mark on edge of casting location of rotor

contact.

8. Loosen the two number 6 hex head set

screws holding rotor. Remove rotor.

9. Write down location and color code of 4

wires connected to repeller potentiometer. Note
location of terminal lugs and connections on inside
of repeller potentiometer.

TM 11-6625-2820-14&P

10. Remove the four 4-40xl/2 inch screws

holding connection to repeller potentiometer.

11. Mark position of the contact lug on P.C.

board mounted under potentiometer resistor.

12. Loosen nylon screw holding contact lug.
Lift out wire wound resistor, insulator and P.C. Refer to paragraph 5-38 to check fre­board.

13. Use 1/2 inch drive socket wrench and

remove nut holding gear shaft. Remove gear.

14. Install new gear. Reverse disassembly pro-

cedure and mount all necessary parts.

NOTE

quency range and accuracy.

5-25/5-26

SECTION VI

REPLACEABLE PARTS

TM 11-6625-2820-14&P

6-1. INTRODUCTION

6-2. This section contains information for ordering
parts. Table 6-l lists abbreviations used in the parts
list and throughout the manual. Table 6-2 lists all
replaceable parts in reference designator order.
Table 6-3 contains the names and addresses that
correspond to the manufacturer’s code number.

6-3. ABBREVIATIONS

6-4. Table 6-1 gives a list of abbreviations used in
the parts list, schematics, and throughout the

manual. In some cases, two forms of the abbre­viation are given,
partial or no capitals.
abbreviations in the parts list are always all capi­tals. However, in the schematics and other parts of

the manual, other abbreviation forms are used with

both lower case and upper case letters.

6-5. REPLACEABLE PARTS LIST

6-6. Table 6-2 is the list of replaceable parts and is
organized as follows:

Electrical assemblies and their compo-

a.
nents in alpha-numeric order by reference desig­nation.

b.

Chassis-mounted parts in alpha-numeric

order by reference designator.

Miscellaneous parts.

c.

one all capital letters and one

This occurs because the

d. Illustrated parts breakdown.
The information given for each part consists of

the following:

a.

The Hewlett-Packard part number.

b. The total quantity (Qty) in the instru-

ment.

c.

The description of the part.

d. Typical manufacturer of the part in a

five digit code.

e.

Manufacturer code number for the part.

The total quantity for each part is given only
once; at the first appearance of the part number in
the list.

6-7. ORDERING INSTRUCTIONS

6-8. To order a part listed in the replaceable parts
table, quote the Hewlett-Packard part number,
indicate quantity required, and address the order
to the nearest Hewlett-Packard office.

6-9. To order a part that is not listed in the
replaceable parts table, include the instrument
model number, instrument serial number, the des­cription and function of the part, and the number
of parts required. Address the order to the nearest
Hewlett-Packard office.

6-10. Refer to table 6-4 for part

number to NSN cross-reference.

6-1

TM 11-6625-2820-14&P

Table 6-1. Reference Designations and Abbreviations (1 of 2)

6-2

Table 6-1. Reference Designations and Abbreviations (2 of 2)

TM 11-6625-2820-14&P

6-3

TM 11-6625-2820-14&P

Table 6-2. Replaceable Parts

6-4

Table 6-2. Replaceable Parts

TM 11-6625-2820-14&P

6-5

TM 11-6625-2820-14&P

Table 6-2. Replaceable Parts

6-6

Table 6-2. Replaceable Parts

TM 11-6625-2820-14&P

6-7

TM 11-6625-2820-14&P

Table 6-2. Replaceable Parts

6-8

Table 6-2. Replaceable Parts

TM 11-6625-2820-14&P

6-9

TM 11-6625-2820-14&P

PART NUMBER - NATIONAL STOCK NUMBER

TABLE 6-4 (Contd.)

CROSS REFERENCE INDEX

DRSEL-MA Form 6230, (1 Sep 76)

6-11

HISA-FM 1909-

TM 11-6625-2820-14&P

PART NUMBER - NATIONAL STOCK NUMBER

Table 6-4 (Cont'd.)

CROSS REFERENCE INDEX

6-12

DRSEL-MA Form 6230, (l Sep 76)

HISA-FM 1909-

APPENDIX O
REFERENCES

TM 11-6625-2820-J4&P

Appendix O

DA Pam 310-4

DA Pam 310-7

TM 38-750

TM

750-244-2

Index of Technical Manuals, Technical Bulletins,

Supply Manuals (Types 7, 8, and 9), SupplY
Bulletins,

US Army

Orders.

The Army Maintenance Management System (TAMMS).

Procedures for Destruction of Electronics

Materiel to Prevent Enemy Use (Electronics

Equipment Index of Modification Work

Command).

and Lubrication Orders.

0-1

APPENDIX I

MANUAL CHANGES

TM 11-6625-2820-14&P

I-1. INTRODUCTION

I-2. This section
adapting this manual to instruments for which the
content does not apply directly. Refer to Table A-1

Manual Changes by Serial Number. Table A-2

relates individual component changes on assemblies
to the MANUAL CHANGES. In addition,
information about recommended modifications for
improvements to the instruments is provided in
Table A-3.

contains information for

I-3. MANUAL CHANGES

I-4. To adapt this manual to your instrument,
refer to Table A-1 and make all of the manual
changes listed opposite your instrument serial
number. Perform these changes in the sequence
listed.

I-5. If your instrument serial number is not listed
on the title page of this manual or in Table A-1
below,
MANUAL CHANGES supplement.

it may be documented in a yellow

i-1

TM 11-6625-2820-14&P

Table A-l. Manual Changes by Serial Number

Table A-2. Manual Changes by Assembly

i-2

I-6. MANUAL CHANGE

CHANGE A

Table 6-2:

Change:

R614 and R615 to HP Part No. 2100-0409

R620 and R621 to HP Part No. 2100-0410.

CHANGE B

Figure 5-16 and Table 6-2:

Delete

R700

Figure 5-20:

Change the Component Location Diagram to the one shown in Figure 7-1.

CHANGE C

Table 6-2:

Change:

C401 to 0150-0052, C:FXD CER 0.05 µF 20% 400 VDCW, 56289, 33C17A

R402 to 0687-3931, R:FXD COMP 39K ohm 10% 1/2 W, 01121, EB 3931
R403 to 0687-4741, R:FXD COMP 470K ohm 10% 1/2 W, 01121, EB 4741

Figure 5-16.

Change the value of:

C401 to 0.05
R402

R403

to

39K

to 470K.

TM 11-6625-2t320-l4&P

CHANGE D

Table 6-2:

Add :

08614-608, CABLE ASSY: RF INPUT
08614-609, CABLE ASSY : RF OUTPUT
08614-610, FILTER: LOW PASS.

NOTE

If any of the above components in Change D fail, they must be replaced by the
components listed in paragraph 5-51. In addition, a procedure for disassembly
and assembly of the component parts is included in paragraph 5-51.

Table 6-2:

Delete:

08614-622

08614-623.

Figure 5-18:

Change the diagram with the partial schematic shown in Figure 7-2.

CHANGE E

Figure 5-19 and Table 6-2:

Delete F2

Figure 5-21 and Table 6-2:

Delete CR203.

i-3

TM 11-6625-2820-l4+&P

i-4

Figure A-l. High Voltage Board (A1OO)

TM 11-6625-2820-14&P

Table 6-2:

Delete under reference designation F2:

1400-0008, Fuseholder

CHANGE F

Table 6-2:

Change F2 to 2110-0029, FUSE: CARTRIDGE 3 AMP 125V SLOW BLOW, 75915, 313005

Figure 5-19:

Change the value of F2 to 4A

CHANGE G

Figure 5-16 and Table 6-2:

Delete R6

CHANGE H

Figure 5-16:

Change R700 to 0687-1031, R:FXD COMP 10K ohm 10% 1/2 W, 01121, EB 1031

Figure 5-19:

Change Cl to 0180-0128, C:FXD ELEC 2800 µF +50-10% 30 VDCW, 56289, D35718 DFP

Table 6-2:

Change the value of:

Cl to 2800

R700 to 10K

CHANGE I

Paragraph 2-10:

Change the fourth sentence to:

A 1-1/2 ampere standard fuse is used for 115 volt operation;
230 volt operation.

Table 6-2:

Change F1 to:

2110-0043, FUSE: CARTRIDGE 1.5 AMP 250V (115V operation), 75915, 31201.5

2110-0033, FUSE: 0.75 AMP 250V (230V operation), 75915, F02GR750A

Change:

J2 to 1251-0148

S2

to

3101-0033

W1 to 8120-0078

Figure

5-19:

Change F1 description:

PAtol.5A
1A to 0.75A

CHANGE J

Table 6-2:

Change:

R6 to 0757-0059, R:FXD MET FLM 1 MEGOHM 1% 1/2 W, 28480,0757-0059

Figure 5-16:

Change the value of R6 to lM

a 3/4 ampere standard fuse is used for

i-5

TM 11-6625-2820-14&P

CHANGE K

Table 6-2:

Change:

DSI to 1450-0048, INDICATOR: GLOW LAMP
NEON-RED LENS, 08717, 859-R-5

CHANGE L

Table 6-2:

Change the HP Part Number and Manufacturer Part Number of:

S1 to 3101-0042
S3 to 3101-1153
S401, S402, S403 and S601 to 3101-0043

08616-00005 to 08616-001

CHANGE M

Table 6-2:

Change:

R620 and R621 to 2100-0898, R:VAR WW 500 ohm 5% LIN 1 W, 28480, 2100-0898

CHANGE N

Table 6-2:

Delete:

5000-8709
5000-8711

5060-8713
5060-8736

5060-8740
08616-00007
08616-00008

i-6

Figure A-2. Partial Schematic of Figure 5-17 ALC Circuit (Part of Change D)

Table A-3. 8616A Recommended Changes

TM 11-6625-2820-l.4&P

i-7/i-8

APPENDIX II

ILLUSTRATED PARTS IDENTIFICATION

SIGNAL GENERATOR

TM 11-6625-2820-14&P

8616A

ii-1

11-2

REF.

1

2

STOCK NO,

DESCRIPTION

See

Figure B-2

See

Figures B-3 & B-4

REF.

STOCK NO DESCRIPTION

QTY.

REF.

STOCK NO.

DESCRIPTION

QTY.

3
4

5
6

Figure B-5

See

Figure B-6

See

See

Figure B-7
Figure B-8

See

ii-3

Figure B-1. HP Model 8616A, Signal Generator, General Arrangement

ii-3

ii-5

Figure B-2.

HP Model 8616A, Signal Generator, Control Panel