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Model 3910
Function Synthesizer
Service Manual

Contains Operating and Servicing Information
WARRANTY
Kcithley Instruments, Inc. warrants this product to be free from defects in material and workmanship for a period of 1 year from date of
shipment.

Kcithley Instruments, Inc. warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batlcrics,
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, 01`contact Keithley hcadquaxters in Cleveland, Ohio. You will
bc given prompt assistance and return instructions. Send the product, transportation prepaid, to the indicated service facility. Repairs
will bc made and the product returned, transportation prepaid. Repaired or replaced products are warranted for the balance of the origi-
nal warranty period, or at least 90 days.

LIMITATION OF WARRANN

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 wzuranty 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 WARRANTIES, 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, INDI-
RECT, 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.
Model 3910 Function Synthesizer
Service Manual

8 1991, Keithley Instruments, Inc.
Test Instrumentation Group
All rights reserved.
Cleveland, Ohio, U.S.A.
October 1991, First Printing
Document Number: 3910-902-01 Rev. A
Manual Print History
The print history shown below lists the printing dates of all Revisions and Addenda created for this manual. The Revision
Level letter increases alphabetically as the manual undergoes subsequent updates. Addenda, which are released between Revi-
sions, contain important change information that the user should incorporate immediately into the manual. Addenda are num-
bered sequentially. When a new Revision is created. all Addenda associated with the previous Revision of the manual are
incorporated into the new Revision of the manual. Each new Revision includes a revised copy of this print history page.

Revision A (oc.c"me", Number 39 10.902-01) ,....,,,.,....,..................................................................... October ,991
Safety Precautions

The following safety precautions should be observed before Do not exceed the maximum signal levels of the instruments
using this product and any associated instrumentation. Al- and accessories,as defined in the specifications and operating
though some instruments and accessorieswould normally be information, and as shown on the instrument or test fixture
used with non-hazardous voltages, there are situations where rear panel, or switching card.
hazardous conditions may be present.
Do not connect switching cards directly to unlimited power
This product is intended for use by qualified personnel who circuits. They are intended to be used with impedance limit-
recognize shock hazards and are familiar with the safety pre- ed sources. NEVER connect switching cards directly to AC
cautions required to avoid possible injury. Read the operating main. When connecting sources to switching cards, install
information carefully before using the product. protective devices to limit fault current and voltage to the
card.
Exercise extreme caution when a shock hazard is present. Le-
thal voltage may be present on cable connector jacks or test When fuses are used in a product, replace with ~arnetype and
fixtures. The American National Standards Institute (ANSI) rating for continued protection against fire hazard.
states that a shock hazard exists when voltage levels greater
than 30V RMS, 42.4V peak, or 60VDC are present. A good Chassis connections must only be used as shield connections
safety practice is to expect that hazardous voltage is present for measuring circuits, NOT as safety earth ground connec-
in any unknown circuit before measuring. tions.

Before operating an instrument, make sum the line cord is If you are using a test fixture, keep the lid closed while power
connected to a properly grounded power receptacle. Inspect is applied to the device under test. Safe operation requires the
the connecting cables, test leads, and jumpers for possible use of a lid interlock.
wear, cracks, or breaks before each use.
If a @screw is present cmthe test fixture, connect it to safety
For maximum safety, do not touch the product, test cables, or earth ground using #18 AWG or larger wire.
any other instruments while power is applied to the circuit
under test. ALWAYS renwve power from the entire test sys-
tem and discharge any capacitors before: connecting or dis- `Ihef B m blo on an instrument or accessory indicates that
y
connecting cables or jumpers, installing or removing IOOOVor more may be present on the terminals. Refer to the
switching cards, or making internal changes, such as install- product manual for detailed operating information.
ing or removing jumpers.
Instrumentation and accessories should not be connected to
Do not touch any object that could provide a current path to humans.
the common side of the circuit under test or power line
(earth) ground. Always make measurements with dry hands Maintenance should be performed by qualified service per-
while standing on a dry, insulated surface capable of with- sonnel. Before performing any maintenance, disconnect the
standing the voltage being measured. line cord and all teat cables.
HOW TO USE THIS MANUAL

Details procedures to verify that the Model 3910 Function
Synthesizer meets stated specifications.
SECTION 1
Performance Verification

Describes basic operating principles
the Model 3910.
for the various circuits in SECTION 2
Principles of Operation

Covers fuse replacement, battery replacement, calibration
and repair of the instrument, and lists replacement parts.
SECTION 3
Service Information

WARNING
The information in this manual is intended for qualified serv-
ice personnel who can recognize possible shock hazards. Do
not attempt these procedures unless you are qualified to do 80.
Table of Contents

SECTION 1- Performance Verification
1.1 INTRODUCTION ................. 1-l
1.2 ENVIRONMENTAL CONDITIONS ... ...................... 1-l
1.3 INITIAL CONDlTIONS ............ ...................... 1-l
1.4 LINEPOWER .................... ...................... 1-l
1.5 RECOMMENDED TEST EQUIPMBNT . ....................... l-1
1.6 VERIFICATION LIMITS ............ ...................... 1-z.
1.7 VERIFICATION PROCEDURES ...... ...................... l-2
1.7.1 Frequency Accuracy ............. ...................... l-2
1.7.2 Maximum Output Amplitude ............................. l-3
1.7.3 DCOffset ............................................ l-4
1.7.4 FrequencyResponse.. .................................. l-4
1.7.5 Total Harmonic Distortion ............................... l-6

SECTION 2 - Principles of Operation
2.1 INTRODUCTION ................................. 2-l
2.2 BLOCK DIAGRAM ............................... 2-l
2.3 CIRCUITOPERATION ............................. . 2-l
2.3.1 ControlSection ................................. 2-l
2.3.2 Display and Keyboard Section ...................... ..... 2-l
2.3.3 Synthesizer .................................... 2-l
2.3.4 AnaIogSection ................................. 2-l
2.3.5 PowerSupply .................................. 2-l
2.3.6 GPIB Interface. ................................. 2-2

SECTION 3- Service Information
3.1 INTRODUCTION ............................. 3-l
3.2 LINE FLJSE REPLACEMENT .................... 3-1
3.3 BAWRY RBPLACEMENT ..................... 3-2
3.4 CALIBRATION .............................. . . 3-2
3.4.1 EnvironmentaI Conditions .................... . ... 3-3
3.4.2 Initial Conditions ........................... . 3-3
3.4.3 LinePower ................................ ..,.. 3-3
3.4.4 Recommended Calibration Equipment ........... ..... 3-3
3.4.5 Cover Removal ............................. 3-3
3.4.6 Calibration Adjustment Locations ............... 3-4
3.4.7 DC Offset Calibration ........................ 3-4
3.4.8 Amplitude Calibration ....................... . .. 3-6
3.4.9 Square Wave Duty Cycle Calibration ............. 3-8
3.4.10 Cover Replacement .......................... .. 3-8
3.5 FCTN OUT JUMPERS ............................... 3-8
3.5.1 Waveform Output On/Off Selection ................... ........ 3-8
3.5.2 FCTN OUT Open/Short Selection ..................... ........ 3-9
3.6 GI'IB INTERFACE INSTALLATlON ..................... ........ 3-9
3.6.1 Installation Precautions ............................. ........ 3-9
3.6.2 Board Installation ................................. ........ 3-9
3.7 REPAIR .......................................... ........ 3-12
3.7.1 Factory Service ................................... ........ 3-12
3.7.2 BoardRemoval ................................... ........ 3-12
3.8 REPLACEABLE PARTS .............................. ........ 3-15
3.8.1 PartsList ....................................... ........ 3-15
3.8.2 OrderingParts ................................... ........ 3-15

APPENDICES
A TypicalData.................................................................. A-l
B Model 3910 and 3910/11 Specifications B-l
List of Illustrations

SECTION 1- Performance Verification
Figure l-l Connections for Frequency Accuracy Test . ................. l-3
Figure 1-2 Connections for Output Amplitude and DC Offset Tests ................. 14
Figure l-3 Connections for Frequency Response Tests .... ................. l-5
Figure 14 Connections for Distortion Tests . . .. ................. l-6

SECTION 2 - Principles of Operation
Figure 2-l Block Diagram ,.............................. ................. 2-2

SECTION 3- Service Information
Figure 3-l Fuse Replacement ........................... ....................... 3-l
Figure 3-2 Battery Replacement ......................... ....................... 3-2
Figure 3-3 CoverRemoval ............................. ....................... 34
Figure 3-4 Calibration Adjustments (Main Board) ........... ....................... 3-5
Figure 3-5 Connsctions for TP2 Offset Calibration ........... ...................... 3-5
Figure 3-6 Connections for FCI'N OUT Offset Calibration ..... ...................... 3-6
Figure 3-7 Connections for Amplitude Calibration ........... ...................... 3-7
Figure 3-S Connections for Square Wave Duty Cycle Calibration 3-8
Figure 3-9 Jumper Installation .......................... .................... 3-9
Figure 3-10 Model 3911 Interface Installation ................ .................... 3-10
Figure 3-l 1 Cover Removal ........................ .......................... 3-11
Figure 3-12 KnobRemoval ........................ .......................... 3-12
Figure 3-13 Connector Removal .................... .......................... 3-12
Figure 3-14 Removal of 3-Terminal Regulator Screws .... ................... ....... 3-13
Figure 3-15 Connecting Wires ...................... .......................... 3-13
Figure 3-16 Main Board Mounting Screws ............. .......................... 3-14
Figure 3-17 Display Board Connector and Screw Locations .......................... 3-15
List of Tables

SECTION 1- Performance Verification
Table l-l Recommended Test Equipment for Performance Verification .................... l-2
Table l-2 Reading Limits for Output Amplitude Tests ................................. l-3
Table l-3 Reading Limits for Frequency Response Tests ................................ l-5

SECTION 3 - Service Information
Table 3-l RecommendedLineFuses ............................................... 3-l
Table 3-2 Recommended Test Equipment for Calibration ............................... 3-3
Table 3-3 Relationship Between R29 Value and Amplitude .............................. 3-7
Table 3-4 Relationship Between R4 Value and Square Wave Amplitude .................... 3-7
SECTION 1
Performance Verification

1.1 INTRODUCTION 1.3 INITIAL CONDITIONS

This section covers procedures to verify accuracy of the The Model 3910 and the test equipment should be turned
Model 3910. Verification can be performed when the in- on and allowed to warm up for one hour before making
shument is first received to verify that the Model 3910 test measurements. If the instrument has been subjected
meets its stated accuracy specifications, and it can also be to extreme temperature or humidity, allow additional
performed following calibration, if desired. If the lnshu- time for stabilization. Typically, it take one additional
ment fails to meet stated specifications, refer to the cali- hour to stabilize an instrument that is 10