Tektronix 3930A Service Manual

Model 3930A

Multifunction Synthesizer

Service Manual

Contains Operating and Servicing Information

WARRANTY

Keithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from date of
shipment.

Keithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries,
diskettes, and documentation.

During the warranty period, we will, at our option, either repair or replace any product that proves to be defective.

To exercise this warranty, write or call your local Keithley representative, or contact Keithley headquarters in Cleveland, Ohio. You will
be given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service facility. Repairs
will be made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance of the origi­nal warranty period, or at least 90 days.

LIMITATION OF WARRANTY

This warranty does not apply to defects resulting from product modification without Keithley’s express written consent, or misuse of
any product or part. This warranty also does not apply to fuses, software, non-rechargeable batteries, damage from battery leakage, or
problems arising from normal wear or failure to follow instructions.

THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANT IES, EXPRESSED OR IMPLIED, INCLUDING ANY IMPLIED
WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. THE REMEDIES PROVIDED HEREIN ARE
BUYER’S SOLE AND EXCLUSIVE REMEDIES.

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT, INDI­RECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRUMENTS AND
SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POSSIBILITY OF
SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, BUT ARE NOT LIMITED TO: COSTS OF REMOVAL

AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAMAGE TO PROPERTY

Keithley Instruments, Inc. l 28775 Aurora Road l Cleveland, OH 44139 l 216-248-0400 l Fax: [phone] l http://www.keithley.com

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Fax: [phone]

Model 3930A Multifunction Synthesizer

Service Manual

Q 1991, Keithley Instruments, Inc.

Test Instrumentation Group

All rights reserved.

Cleveland, Ohio, U.S.A.

August 1991, First Printing

Document Number: 3930A-902-01 Rev. A

All Keithley product names are trademarks or registered trademarks of Keithley Instruments, Inc.
Other brand and product names are trademarks or registered trader&k of their respective holders.

Safety Precautions

The following safety precautions should be observed before using the Model 3930A Muhifunction Synthesizer and any
associated instruments.

This instzument is intended for use by qualified personnel who recognize shock hazards and are familiar with the safety
precautions required to avoid possible injury. Read over this manual carefully before using the instrument.

Exercise extreme caution when a shock hazard is present at the test circuit. The American National Standards Institute
(ANSI) states that a shock hazard exists when voltage levels greater than 30V rms or 424V peak are present. A good
safety practice is to expect that hazardous voltage is present in any unknown cikuit before measuring.

Inspect the connecting cables and test leads for possible wear, cracks, or breaks before each use.

For maximum safety, do not touch the test cables or any instruments while power is applied to the circuit under test.
Turn off the power and discharge any capacitors before connecting or disconnecting cables from the instrument.

Do not touch any object which could provide a current path to the common side of the circuit under test or power line
(earth) ground. Always make measurements with dry hands while standing on a dry, insulated surface capable of with­standing the voltage being measured.

Instrumentation and accessories should not be connected to humans.

HOW TO USE THIS MANUAL

Details procedures to verify that the instrument meets
stated specifications.

Describes basic operating principles for the various cirtits in
the Model 3930A.

Covers fuse replacement, calibration and repair of the instru­ment, and lists replacement parts.

WARNJNG

The information in this manual is intended for qualified serv­ice personnel who can recognize possible shock hazards. Do
not attempt these procedures unless you are qualified to do so.

SECTION

1

Performance Verification

SECTION 2

Principles of Operation

SECTION 3

Service Information

.

Table of Contents

SECTION 1 - Performance Verification

1.1

1.2

1.3

1.4 LINEPOWER

1.5 RECOMMENDED TEST EQUIPMENT

1.6

1.6.1 Frequency and Duty Cycle Accuracy

1.6.2 Amplitude Accuracy

1.6.3 Frequency Response (Sine)

1.6.4

1.6.5 TotalHmonicDistortion .....................................................

1.6.6. DC Voltage Accuracy

1.6.7

1

1.6.8

INTRODUCTION ..............................................................

ENVIRONMENTALCONDITIONS..
INTTIALCONDlTIONS

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

VERIEICATIONPROCEDTJEES

Frequency Response (Triangle, Sawtooth, Square)

DCLevel(Square)andDCOffsetError(Sine)

RiseandFaLlTimes ...........................................................

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

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

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

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

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

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

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

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

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

........

SECTION 2 - Principles of Operation

2.1 INTRODUCTION ..............................................................

2.2

2.2.1

2.2.2

2.2.3

2.2.4 Synthesizer Section

2.2.5

2.2.6 Power Supply Section

2.3

2.3.1

2.3.2

2.3.3

2.3.4

2.3.5

2.4

BLOCK DIAGRAM

ControlSection ..............................................................

Display and Keyboard Section

TriggerSection.. ............................................................

AnalogSection ..............................................................

ANALOGCIRCUITDESCRD?TION

Analog Section Block Diagram

D/A Converter ..............................................................

SquareWaveGenerator

AmplitudeModulation ........................................................

Amplitude and DC Offset Control

SYN’IHESIZEROl’ERATINGPRINCII’LES

............................................................ 2-l

................................................... 2-l

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

......................................................... 2-3

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

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

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

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

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

.

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

1-l
l-l
l-l
l-l
l-l
1-2
l-2
l-4
l-5
l-7
l-8
l-9
l-9
l-9

2-l

2-l

2-l
2-l
2-l

2-3
2-3
2-3
2:3
2-3
2-3
2-5

SECTION 3 - Service Information

3.1

3.2 LINEFLJSEREPLACEMENT

3.3 CALIBRATION

3.3.1 EnvironmentalConditions

3.3.2

3.3.3

INTRODUCTION ..............................................................

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

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

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

InitialConditions

LinePower .................................................................

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

3-l
3-l
3-l
3-2
3-2
3-2

3.3.4 Recommended Calibration Equipment

3.3.5

3.3.6

3.3.7

3.3.8

3.4

3.5

3.6

3.7

3.7.1 Factory Service

3.7.2

.3.7.3

3.8

3.8.1

3.8.2

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

Calibration Adjustments

CalibrationProcedures ........................................................

Cover Replacement
FAN FILTER CLEANING
FCTN OTJT JUMPER
RECHARGEABLE BATTERY REPLACEMENT
REPAIR

PowerSupplyTestPoints

Board-Level Repair
REPLACEABLE PARTS

Parts List

Ordering Parts

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

.............................................................. 3-10

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

.............................................................. 3-12

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

........................................................... 3-9

........................................................ 3-9

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

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

........................................................... 3-12

......................................................... 3-12

APPENDICES

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

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

.

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

3-2
3-3
3-3
3-6

3-9
3-10
3-10

3-10

3-12

A
B

TypicalData............................................................,.....

Model3930ASpecifications

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

A-l
B-l

List of Illustrations

SECTION

Figure l-l
Figure l-2

Figure l-3

Figure l-4

1 -

Performance Verification

Connections to Timer/Counter
Connections to Model 197A DMM
Connections to Wideband AC DVM

Co~ections

to Audio Analyzer

SECTION 2 - Principles of Operation

Figure 2-l
Figure 2-2
Figure 2-3
Figure 2-4
Figure 2-5

Overall Block Diagram
Analog Selection Block Diagram
Frequency Synthesizer Address Generator Diagram
Address Generator Waveform
Waveform Memory and D/A Converter

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

SECTION 3 - Service Information

Figure 3-l
Figure 3-2
Figure 3-3
Figure 3-4
Figure 3-5
Figure 3-6
Figure 3-7
Figure 3-8
Figure 3-9

CoverRemoval ...........................................................

Analog Board (NP-21022) Calibration Adjustments
Control Board (NJ?-10408) Calibration Adjustments
Co~eciions to Model 197A DMh4
Second Model 3930A Corux!ctions
Co~eciions to PM 6654C Counter
connections to Dv’M
Power Supply Test Point Locations

ExplodedView ...........................................................

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

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

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

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

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

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

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

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

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

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

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

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

............................................. 3-7

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

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

l-3
l-4
l-5
l-8

2-2
24

2-5
2-6
2-6

3-3
3-4
3-5
3-6

3-8
3-9
3-11
3-13

-. -

List of Tables

SECTION 1

Table l-l
Table l-2
Table l-3
Table l-4
Table l-5
Table l-6
Table l-7
Table l-8 Limits for DC Level (Square) and DC Offset Error (Sine)
Table l-9 Limits for Rise/Fall Times

- Performance Verification

VerificationEquipment .....................................................

Limits for Frequency and Duty Cycle Accuracy
Limits for Amplitude Accuracy
Limits for Frequency Response (Sine)
Limits for Frequency Response (Triangle, Sawtooth, Square)
Limits for Total Harmonic Distortion
Limits for DC Voltage Accuracy

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

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

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

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

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

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

SECTION 3 - Service Information

Table 3-l
Table 3-2
Table 3-3
Table 3-4
Table 3-5

Recommended Line Fuses
Recommended Test Equipment for Calibration
Power Supply Test Point Summary
Board Level Repair Summary
Replaceable Parts

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

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

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

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

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

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

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

l-2
13
l-4
l-6
l-7
l-8
l-9
l-9
l-10

3-l
3-2
3-10
3-12
3-12

SECTION 1

Performance Verification

1.1 INTRODUCTION

The procedures outlined in this section may be used to
verify that the Model 3930A is operating within the limits
stated in the specifications. Performance verification may
be done when the instrument is first received to ensure

that no damage or n&adjustment has occurred during

shipment. Verification may also be performed whenever

there is a question of instrument accuracy, or following
calibration, if desired.

NOTE
If the instrument is still under warranty (Less
than one year from the date of shipment), and
its performance falls outside the specified
range, contact your Keithley representative or
the factory to determine the correct course of
action.

1.2 ENVIRONMENTAL CONDITIONS

All measurements should be made at 18-28°C (65-82W

and at less than 70% relative humidity.

cation procedures. If the instrument has been subject to
extremes of temperature (outside the range specified in
the previous paragraph), additional time should be al­lowed for internal temperatures to reach normal operat­ing temperature. Typically, it takes one additional hour
to stabilize a unit that is 10°C (18’FQ outside the specified
temperature range.

1.4 LINE POWER

Be sure to set the line voltage switch for the correct volt­age. The instrument should be operated at a voltage
within SO% of the line voltage setting and at a frequency
from 48 to 62Hz.

1.5 RECOMMENDED TEST EQUIPMENT

Table l-l lists all the test equipment needed for verifica­tion. The procedure for performance verification is based
on using this exact equipment.

NOTE
The verification limits reflect only the accu­racy specifications of the Model 3930A. They
do not include test equipment tolerance.

1.3 INITIAL CONDITIONS

The Model 3930A must be turned on and allowed to

warm up for at least one hour before beginning the verifi-

Alternate equipment may be used as long as the substi­tute equipment has specifications at least as good as
those listed in Table l-l.

l-l

SECTION P

PeqSmname Vm~cafion

Table l-l. Verific

Manufacturel
Keithley
Fluke

Philips
l%nasonic
Keithley
Keithley
Pomona

Model
197A
892OA

PM 6654C
PM 9678
VW722A

7051-2
7755
1468

Description
DMM (DC volts, AC volts)

(5-l /2 digits)
DVM (AC volts)

(3-l /2 digits)
Timer/Counter
TCXO option
Audio Analyzer

BNC Interconnect Cable
5OQ Feed-through Terminator
BNC-banana Adapter

1.6 VERIFICATION PROCEDURES

The following paragraphs contain the detailed proce­dures for verifying accuracy specifications of the Model
3930A using the equipment listed in Table l-1. The allow­able reading limits in these procedures do not in&de er­ror that could be contributed by this equipment.

These procedures are intended for use only by qualified
personnel using accurate and reliable test equipment. If
the instrument is out of specifications and not under war­ranty, refer to the calibration information in the service
manual.

tion Equipment

1 Specifications
~ 20V range; *(0.015% of rdg + 3 counts)

ACV; k(O.35% of rdg + 100 counts>
20V range; lkHk-2OOkHz (0.5% of rdg),
2OOkHz-1MHz (0.7%), I-1oMHz (3%), lo-2oMHz (5%)
O.OlHz-12OMHz; time base aging
cl x IO-‘/month; Vp-p measurements
lOHz-11OkHz; 0.001% at full scale; fldB harmonic dis­tortion accuracy from lOH2 to 15.99kHz
5OQ coaxial cable (RG-58C), male BNC connectors, 2ft
(0.6m)

BNC to BNC adapter, 5OQ termination, DC to
25oMH2, VSWR of cl.1
Female BNC connector to double banana

1.6.1

Frequency and Duty Cycle

plug

Accuracy

1. Connect the function synthesizer to a timer/counter

as shown in Figure l-l. Turn on both instruments.

2. Restore factory defaults on the Model 3930A by

pressing SHIFT PRST.

3. Program a 1MHz sine function of 2OVp-p.

4. Set the timer/counter to display the frequency at

Channel A and verify that the frequency reading is

within the limits specified in Table l-2.

5. Program a 1OOHz square wave with a fixed 50% duty

cycle.

6. Set the timer/counter to display the pulse width of

Channel A, and verify that the reading is within
specifications.

7. Modify the frequency and duty cycle settings of the

synthesizer according to Table l-2, and verify the
pulse width readings.

l-2

Model 3930A

Fipure I-I. Connections to Timer/Counter

Performance Verification

SECTTON 1

Model PM 6654C Counter/Timer

Set for 5OQ
input impedance

Table 1-2. Limits for Frequency and Duty Cycle Accuracy

Function

Amplitude Frequency
Sine 2ovp-p MHZ
Square @XD50) 2OVp-p 1OOHZ

1kH.Z
5kHz
1okHz

Square (VAR50) 2OVp-p

1QOHZ
1kHZ

5kHz

1okHz

Allowable Reading

(ltJ°C to 28OC)

999.995lcHz to 1.000005MHz

4.97msec to
497psec to

99.4psec to

49.7psec to

4.98msec to
498psec to

99.6p.sec to

49.8psec to

5.03msec
503psec

100.6psec

50.3pec

5.02msec
502pec

100.4psec

50.2psec

l-3

SECTTON 1

Performance Verification

1.6.2 Amplltude Accuracy

1. Connect the function synthesizer to a DMM as
shown in Figure l-2. Turn on both instruments.

2. Restore factory defaults on the Model 3930A by
pressing SHIFT PRST.

Figure 1-2.

Model 3930A

Connections to Model 297A DMM

I

,

Function

/ output

Model 7051-2 Coaxial

3. Program a 1kHz sine function amplitude of

7.49vp-p.

4: Set the DMM to measure AC volts with autoranging,

and verify that the voltage reading is within the lim­its specified in Table l-3.

5. Change the function, frequency, and amplitude set­tings of the synthesizer according to Table l-3, and
verify the voltage

Model .

197A DMM

Cable

readings.,

Pomona 1468

hield

I

Table 1-3.

Function

Amplitude

Sine 7.49vp-p

Limits for Amplitude

Frequency

1kHZ
Square (FXD50)
Triangle
Sawtooth Up
Sawtooth Down

Sine

3ovp-p

1kHZ

1okHz

2okHz

50!&2
Sine lOVp-p lkH2

1okHz

2okHz

501612

Sine

3VP-P

1kl-b

1okHz
2okI-k
5OHz

Accuracy

Allowable Reading

(18OC to 28’0

2.6349Vrms to 26613Vrms

3.558W.n~ to 3.782Vrms

2.0541Vrms to 2.1837Vrms

2.0541Vrn-t~ to 2.1837Vrms

2.0541vrms to 2.1837Vrms

10.5536Vrms to 10.6596Vrms

10.5536Vrms to 10.6596Vrms

10.5536Vrms to 10.6596Vrms

10.5536vrms to

3.5179vrms to 3.5532Vrms

3.5179vrms to 3.5532Vrms

3.5179lhlns to

3.5179vrms to 3.5532Vrms

1.05536vrms to 1.06596Vrms

1.05536Vrms to

1.05536Vn.n~ to 1.06596Vrms

1.05536Vnns to 1.06596Vrms

10.6596Vrms

3.5532Vrms

1.06596Vrms

l-4

Triangle 3ovp-p
Square
Sawtooth Up
Sawtooth Down

1kHZ

8.617OVrms

8.746SVrms

to

1425vrms to 15.15vrms

8.617OVrms to

8.7468Vrms

8.617OVrms to 8.7468Vrms

SECTTONI

Performance Verification

1.6.3

Frequency Response (Sine)

1. Connect the function synthesizer to a wideband AC
DVM as shown in Figure 1-3. Turn on both instru­ments.

2. Restore factory defaults on the Model 3930A by
pressing SHIFT PRST.

3. Program a lkH2 sine function of BOVp-p.

4. Set the DVM to measure AC volts with autoranging,
and verify that the voltage reading is within the lim­its specified in Table l-4.

5.

Set the DVM to measure dB and select

a 5052

refer­ence imoedance. Press REL to establish the oresent
voltage ieading as the relative dB reference.

Id 3930A

l

6. Change the frequency setting of the synthesizer ac­cording to Table l-4, and verify the subsequent &dB
readings.

7. Program a 1kHz sine function of 3.75Vp-p, and ver­ify that the voltage reading is within limits. Press
REL to establish the reading as the relative dB refer­ence. Verify the fdB readings for the remaining fre­quencies.

8. Program a 1kHz sine function of 3.74Vp-p, and ver­ify the reading. Establish the present reading as the
relative dB reference. Verify the fdB readings for the
remaining frequencies.

Model 7755

5Oi-l

Feed Through

Model 8920A Voltmeter

Figure Z-3.

Function

output

Connections to Wideband AC DVM

Model 70512
Coaxial Cable

l-5

SECTTON 1
Performance VerijScafion

Function

Table l-4. Limits for Frequency Response (Sine)

Allowable Reading

Amplitude

Frequency

(1WC to 28W

Sine

Sine

he

3ovp-p

1kHZ
1OkHZ -0.ldB to i-O.ldB

1ookHz
2OOkHz -0.3dB to +0.3dB
35okHz
5ookHz
7OOkHz
8OOkI-h
9ookt3z
1MHz

1.m

3.75vp-p 1kTdz
1OkHZ -0.ldB to
100kHz -0SdB to +O.ldB

200kHz -0.3dB
35okHz

5OOkHz

7OOkHz -0.3dB to +0.3dB

8OQkHZ

9ookHz -0.5dB
m4J3z

1.2MHz -1.OdB to +0.3dB

3.74vp-p

1kHZ
1OkHZ -0SdB

1001cHz -O.ldB
2OOm -0.3dB to +0.3dB
35okI-k -0.3dB to +0.3dB
500kHz -0.3dB to +0.3dB
7OOkJsz -0.3dB to +03dB
8OOkHz -0.5dB
9ookHz -0.5dB

*I

1MHZ -0.5dB to +0.3dB

1.2MHz -1 .OdB

5.2vrms to 5.4vrms (=REF)

-0.ldB to +O.ldB

-0.3dB to +0.3dB

-0.3dB to +0.3dB

-0.3dB

-0.5dB

-0.5dB

t0

to

to

+0.3dB
+0.3dB
+0.3dB

-0.5dB to +0.3dB

-l.OdB

0.65Vnns to

to

+0.3dB

0.676Vrms (=RJIF)

+O.ldB

to

+0.3dB

-0.3dB

-0.3dB

-0.5dB

-0.5dB

to +0.3dB
to +0.3dB

to +0.3dB
to

+0.3dB

to +0.3dB

0.648vrms to 0.674Vrms (=RJIF)
to +O.ldB
to

+O.ldB

to

+0.3dB

to +0.3dB
to

+0.3dB

l-6

Perhrmance Verification

SECTION 1

1.6.4

Frequency Response (Triangle,

Sawtooth, Square)

1. Connect the function spthesizer to a timer/counter
as shown in Figure l-1. Turn on both instruments.

2. Restore factory defaults on the Model 3930A by
pressing SHJFT PRST.

3. Program a 1kHz triangle wave of 3OVp-p.

4. Set the timer/counter to display the peak-to-peak
voltage at Channel A, and verify that the voltage

Table 1-5.

Function Amplitude Frequency
Triangle 3ovp-p 1kHz

Sawtooth Up

Limits for Frequency Response (Triangle, Sawtooth, Square)

5kHz

1okHz

3OVP-P

1kHz l4.,25Vp-p to

5kHz 0.95 XRECF to 1.05 x REF

1okHz

reading is within the limits specified in Table l-5.
Call this reading REF.

5. Change the frequency to 5kHz. The new reading
should be between 0.97 times the REF reading and

1.03 times the REF reading.

6. Modify the frequency and function settings of the
synthesizer according to Table 1-5, and verify that
the corresponding readings are within the specified
limits.

Allowable Reading

WC to 28OC)

14.25vp-p

0.97xm to 1.03 x REF

0.97xREF to 1.03 x REF

0.95 x RBF to

15.75vpp (=REF,I

.to

15.75vp-p (=REP)

1.05XREF

Sawtooth Down

Square

3ovp-p 1kHz

5kHz 0.95 xREF to 1.05 x REF
lOkJ!Iz 0.95 XRW to 1.05 x REF

3ovp-p 1kHZ

5kHz 0.98 xRRF to 1.02 x REF
1OkHZ 0.98 xRRF to 1.02 x REP
1ookHz 0.98 xREF to 1.02 x REF

14.25vpp to 15.75vp-p (=REF)

14.25vpp to 15.75vp-p (=REFI

l-7