QuadTech 1657 RLC User Manual

1657 RLC Digibridge®

Instruction Manual

Foun 1657-0120-07/B1

®QuadTech, Inc., 1992

5 Clock Tower Place, 210 East

Maynard, Massachusetts, U.S.A. 01754

January, 1997

Tel. [phone]

800-253-1230 (Sales)
800-253-1230 (Service)

Fax. [phone]

The material in this manual is for informational purposes only and is subject to change, without notice.
QuadTech assumes no responsibility for any error or for consequential damages that may result from the
misinterpretation of any procedures in this publication.

Contents

Instruction Manual Changes

Specifications

Warranty

Introduction -Section 1

Installation -Section 2
Operation -Section 3
Theory -Section 4
Service and Maintenance -Section 5

~ Product will be marked with this symbol (ISO#3684) when it is necessary for the user to refer
to the instruction manual in order to prevent injury or equipment damage.

Parts Lists and Diagrams -Section 6

These two supplementary pages contain information of improvements or modifications not
documented in the current manual. All references to GenRad in the manual now apply to
QuadTech, Inc.

Page -Specifications (Power & Mechani cal)

Power should be 90 -250V AC, 50 -60 Hz. Voltage switching is automatic and no
longer selected by rear panel switch. 60 Watts maximum.

Weight should be 10 lbs. (4.5 kg) net, 15 lbs. (6.8 kg) shipping.
Environment reads, Altitude < 2000m, Installation Category 1, Pollution Degree 1

Page - Table of Contents (Parts List and Diagrams -Section 6)

Power supply board (1657-4720) layout and diagram (page 6-13) replaced by Power

supply assembly part number 700011 (no diagrams, repair by module exchange)

Page 1-4 -Figure 1-2, Rear Panel Controls and Connectors

Rear view should show new power supply assembly (PN 700011) without line-voltage

switch.

Page 1-4 -Table 1-2, Rear Panel Connectors and Controls

Ref No. 2R -& Fuse is 6/10A, 250V, 3AG Type, Slow Blow. Replace only with

the same type and rating. To replace, remove fuse drawer by pressing up on release tab.
Ref No. 3R -Line-voltage switch has been deleted, power input is from 90 -250V AC

Page 1-4 -Table 1-3, Accessories

A quantity of two spare fuses are supplied, 6/10A, 250V, 3AG Type, Slow Blow

(QuadTech part number 5330-1100)

Page 2-1 -Safety Inspection

Before operating the instrument inspect the power inlet module on the rear of the unit to

ensure that the properly rated fuse is in place, otherwise damage to unit is possible. Fuse is
6/l0A, 250V, 3AG Type, Slow Blow.

The 1657 is shipped with a standard U.S. power cord, QuadTech PN 4200-0300 (with Belden
SPH-386 socket or equivalent, and 3 wire plug confonning to IEC 320) or an approved
international cord set. Make sure the instrument is only used with these or other approved
international cord sets, which ensures the instrument is provided with connection to protective
earth ground.

In all installations the instrument should be positioned with consideration for ample air flow to the
side and rear panel ventilation holes. An open space around the instrument of at least 3 inches
(75mm) is recommend. The surrounding environment should be free from excessive dust to
prevent contatnination of electronic circuits.

Page 2-1 -Power-Line Connection

Power line switch for 115V or 230V operation has been removed, switching is
automatic for voltages between 90 -250V AC.

Page 2-2 -Figure 2-2

Figure 2-2 does not apply. Only certified line cords which comply with IEC 227 or
IEC 245 should be used.

Page 3-2 -Paragraph 3.1 Basic Procedure, step a

Power line switch for 115V or 230V operation has been removed, switching is

automatic.

Page 5-1 -Paragraph 5.2, Instrument Return

Contacts for QuadTech are: Sales 800-253-1230

Service 800-253-1230
Technical Assistance 978-461-2100

Page 5-2 & Page 5-3 -Caution Note

Power line switch for 115V or 230V operation has been removed, switching is
automatic.

Page 5-7 -& Paragraph 5.6.1 & Figure 5-3, Disassembly

Power Supply Assembly shown has been replaced by Power Supply Assembly PN

700011.

Page 5-10 -Instrument Cleaning Instructions

Monthly (more or less depending on usage) the built-in test fixture should be cleaned
with a soft brush and isopropyl alcohol. Avoid getting excess alcohol on instrument paint
surfaces, otherwise damage to the finish can result. For additional instrument cleaning
instructions refer to paragraph 5.7.1 (Care of the Test Fixture) and paragraph 5.7,2 (Care of the
Display Panel).
Power Supply Assembly shown in Figure 5-8 has been replaced by Power Supply

Assembly PN 700011.

Page 5-12 - Paragraph 5.8.2, Power Supply

Trouble Analysis procedure does not apply to new Power Supply Assembly P/N 700011.

Page 6-2 - Figure 6-2, Rear View

Rear view should show new power supply (PN 700011) without line-voltage switch

Page 6-3 - Mechanical Parts List, Rear

Items 1 - 4 (power connector, fuse extractor post, line voltage switch & cover) deleted on new assembly

Page 6-12 & Page 6-13 - Parts and Diagrams

Power Supply Board and Parts List shown, PN 1657-4720 has been replaced by
Power Supply Assembly, PN 700011. The 700011 Assembly must be repaired by module exchange.

Measurement Mode: Measures R series or parallel; L and Q series or parallel; C
and D series or parallel. All measurement modes are pushbutton selectable.

Displays: LED-type numerical display with automatically positioned decimal points
and illumination of units. For R LC, five digits (99999) and simultaneously for DQ,
four digits (9999).

Ranges: Pushbutton selection with automatic front-panel guidance. Three basic ranges
(best accuracy, see table) of 2 decades each, for each parameter. Automatic extensions
to min and max, as tabulated.

Measurement Speed: Greater than 3 measurements per second.

/

Test frequencies: Pushbutton selection between 2. Accuracy re panel
legends: +2%, -.01%. Actual frequencies: for 1657-9700, 1020.0 Hz +/- .01% (panel
legend "1 kHz") and 120.00 Hz +/- .01%;
for 1657.9800,1000.0 and 100.00 Hz +/- .01%.

Applied Voltage: 0.3 V rms maximum.

Accuracy: For R, L, and C: +/- 0.2% of reading in basic ranges, if quadrature
component is small (D < 0.1, Q > 10, etc). See table. D accuracy: +/- .001 in basic
ranges, for D < 0.1 (otherwise, see table). Q accuracy: +/-.01 in basic ranges, for Q < 1
(otherwise, see table).

Environment: TEMPERATURE: 0° to 50°C operating, -40° to +75°C
storage. HUMIDITY: 0 to 85% R.H., operating.

Supplied: Power cord, axial-lead adaptors, instruction manual.

Power: 90 to 125 or 180 to 250 V, 50 to 60 Hz. Voltage selected
by rear-panel switch. 25 W maximum.
Mechanical: Bench mounting. DIMENSIONS: (wxhxd): 375x112x343 mm
(14.8x4.4x13.5 in.). WEIGHT: 5.6 kg (12.3 lb) net,l0 kg (22 lb) shipping.

Patent applied for.

SERVICE POLICY

QuadTech policy is to maintain product repair capability for a period of five (5) years after original
shipment and to make this capability available at the then prevailing schedule of charges.

Table of Contents

1.1 PURPOSE 1-1

.

d

ifi

1.2 GENERAL DESCRIPTION 1-1

1.3 CONTROLS, INDICATORS, AND CONNECTORS 1-1

1.4 ACCESSORIES 1-1

1.1 PURPOSE. in keeping with the long-life circuitry inside. Glass-epoxy
The 1657 Digibridge digital impedance meter embodies circuit boards interconnect and support high-quality com

use of a microprocessor and other LSI circuitry to ponents to assure years of dependability.
provide excellent performance at low cost. Adaptability to any common ac power line is assured by

A few clearly labeled pushbuttons and the versatile the removable power cord and the convenient line-voltage
built-in test fixture make this instrument a model for con- switch. Safety is enhanced by the fused, isolating power
venience. Measurement results are clearly shown with dec- transformer and the 3-wire power connection. A compre
imal points and units, which are automatically presented to hensive functional description is given in Theory, Section 4
assure correctness. Display resolution is 5 digits for R, C, Electrical and physical characteristics are listed in Specifi
and L (4 for D or Q) and the basic accuracy is 0.2%. cations at the front of this manual, dimensions in Installa

Long-term accuracy and reliability are assured by the tion, Section 2. Controls are described below, and their use
measurement system. It makes these accurate analog in Operation, Section 3.
measurements over many decades of impedance without a
single calibration or "trimming" adjustment (not even in 1.3 CONTROLS, INDICATORS, AND CONNECTORS.
original manufacture). .

The built-in test fixture, with a pair of plug-in adaptors, Figure :-1 shows the front panel conrols and indicators.
receives any common component part (axial-lead or radial- Table 1-1 identifies them with descriptions and functions.
lead) so easily that insertion of the DUT is a one-hand Similarily, Figure 1-2 shows the rear panel and Table 1-2 identifies

operation. True 4-terminal connections are made automat

t

.

ically. Extender cables and other accessories are available

.

I

.

ent

es and describes the rear panel controls and connec

I

and describes the rear panel controls and connectors.

for measurements at a distance from the Digibridge.

1.4 ACCESSORIES.
Gen Rad makes several accessories that enhance the use

1.2 GENERAL DESCRIPTION. fulness of this instrument. Two extender cables facilitate
Convenience is enhanced by the arrangement of test making connections to those devices and impedance stan

fixture on the front ledge, with push buttons farther for- dards that do not readily fit the built-in test fixture. A
ward and display behind. The display panel is inclined and remote test fixture (used with BNC adaptor and cable
recessed to enhance visbility of digital readouts and mode assembly) provides convenience and relatively easy main
indicators. These indicators serve to inform and guide the tenance, and saves wear on the built-in test fixture. All of
operator as he operates the simple controls. these test-fixture accessories provide for true 4-terminal

The instrument stands on a table or bench top. The connections (and guard) to the device being measured,

sturdy metal cabinet is attractively and durably finished, without appreciable reduction in measurement accuracy.

Other useful accessories are offered, such as standards for
checking the performance of the Digibridge. Refer to
Table 1 -3 and Section 5.

INTRODUCTION 1-1

1-2 INTRODUCTION

INTRODUCTION 1-3

1-4 INTRODUCTION

2.1 UNPACKING AND INSPECTION.

If the shipping car ton is damaged, ask that the carrier's
agent be present when the in stru ment is unp ack ed. Insp ect the in str ument
for damage (scratches, dents, broken parts, etc.). If the instrument is
damaged or fails to m eet sp ecific ations, notify th e carr ier and th e neares t
GenRad field
office. (See list at back of this manual). Retain the shipping carton and the
padding material for the carr ier's inspect ion.

2.2 DIMENSIONS Figure 2-1.

The instrument is supplied in the bench configuration,
i.e., in a cabinet with resilient feet for placement on a table. The overall
dimensions are given in the figure.

2.3 POWER-liNE CONNECTION.

The power transformer primary windings can be switched, by means of
the line voltage switch on the rea r p anel, to ac. commodate ac line voltages
in either of 2 ranges, as labeled, at a frequency of 50 or 60 Hz, nominal.
Using a small screwdriver, set this switch to match the measured voltage of
your power line.

I f your I ine voltage is in the lower r ange, connect the 3-wire power

cable (P/N 4200-9625) to the power connector on the rear panel (Figure 1-2)
and then to the power line.

The instrument is fitted with a power connector that is in conformance
with the Intern ational Electrot echnical Commis sion publication 320. The 3
flat contacts are surrounded by a cylindrical plastic shroud that reduces the
possibility of electrical shock whenever the power cord is being unplugged
from the instrum ent. In addition, the center ground pin is longer, which
means that it mates first and disconnects last, for user protection. This panel
connector is a standard 3-pin grounding-type receptacle, the design of which
has been accepted world wide for electronic instru. mentation. The connector
is rated for 250 V at 6 A. The receptacle accepts power cords fitted with the
Belden type SPH- 386 connector.

The associ ated power cord f o r use with tha t receptacle, fo r line voltages

up to 125 V, is Gen Rad part no. 4200-9625.
It is a 210-cm (7 ft), 3-wire, 18-gage cable with connector bodies molded
integrally with the jacket. The connector at the power-line end is a stackable
hammerhead design that conforms to the "Standard for Grounding Type
Attachment Plug Caps and Receptacles ," ANSI C73. 11-1966, which
specifies limits of 125 V and 15 A. This power cord is
listed by Underwriters Laboratories, Inc., for 125 V, 10 A.

If the fuse must be replaced, be sure to use a "slow blow" fuse of the
current and volta ge ratings shown on the rear panel, regard less of the line
voltage.

INSTAllATION 2-1

If your line voltage is in the higher ra nge selectable b y the line voltage
switch, use a power cord of the proper rating (250 V, 15 A) that mates
with both instrument and
your receptacle. It is possible to replace the "hammerhead" connector on the
power cord that is supplied with a suitable connector. Be sure to use one
that is approved for 250 V, 15 A. A typical configuration is shown in Figure
2-2.

2.4 LINE-VOLTAGE REGUlATION

The accura cy of measurements accomplished with precision electronic
test equipment operated f r om ac line
sources can often be seriously degraded by fluctuations in primary input
power. line-voltage variations of +/-15% are commonly encountered, even
in laboratory environments.
Although most modern elect ron i c inst rumen ts in corp orat e some d egree of
regulation, possible power.source problems should be considered for
every instr umentation setup. Th e use of line-volta ge regulators b etween
power lines and the
test equipment is recommended as the only sure way to rule out the effects
on measuremen t data of variations in line voltage.

2.5 TEST-FIXTURE CONNECTIONS.

2.5.1 Test Fixture on the Digibridge.

Because an unusually versatile test fixture is provided on the front shelf
of the instrument, no test-fixture connection is generally required. Simply
plug the device to be measured (DUT) into the test fixture, with or without
its adaptors. For details, refer to paragraph s 3.1, 3. 2. Accessories can be
attached to exte nd and adapt the test fixt ur e, as described bel ow.

2.5.2 Remote Test Fixture.

Connection of the DUT at a remot e test fixture requires proper adaptors
and cable connections from the Digibridge. Obtain the following
accessories. (See Table 1-3.)

BNC Adaptor 1689-9601
BNC Cable Assembly 1689-9602, or equivalent
Remote Test Fixture 1689-9600, or equivalent

handler or special fixture.

This remote test fixture functions like the one supplied on the
Digibridge. True "Kel vin" conn ections are m ade at the point s of contact
with the DUT leads. Install as
follows:

a. Remove any adaptors, if present, from the test

fixture.

b. Plug the BNC adaptor into the basic test fixture with th e BNC
connectors facing forward. lock the connection with the 2 captive thumb
screws. (The screws must be

seated to complete the ground connection.)

c. Connect the cable assembly to the adaptor on the Digibridge and to
the remote test fixture as indicated in Table 2-1.

NOTE

User provided cables and/or remote test
fixtures can be us e d, particularly if the
DUT is to be handled automatically.
See paragraph 3.7 for comments on cable
and fixture capacitance.

2.5.3 The 1657-9600 Extender Cable (Banana Plugs).

The accessory extender cable 1657-9600 is available to connect to
DUTs that are multiterminal, physically large, or otherwise unsuited for
the built-in test fixture. This cable is particularly convenient for connecting
multiterminal components with binding posts that accommodate banana
plugs. Use the following procedure to install the extender cable on the
instrument.

a. Remove the ad aptors, if pr esent, from the t est

fix tu re.

b. Plug the single-connector end of the extender cable into the
Digibridge test fixture so that its blades enter both slots and the cable lies
away from the di splay panel. lock the connector with the two captive
thumb screws.

c. Note the color coding of the five banana plugs. Be sure that the
"low" terminals (both potential and current) connect to one end of the
DUT and the "high" terminals to the other end. Connect guard to a shield if
any, but not to either end of the DUT.

2-2 INSTAllATION

P-(potential, low) = Black/white
I-(current, low) = Black
P+(potential, high) = Red/white

I+(current, high) = Red
Guard = Black/green

2.5.4 The 1688-9600 Extender Cable
("Type 874" Connectors).

The accessory extender cable 1688-9600 can be used to connect a
DUT that is multiterminai, physically large, or otherwise unsuited for the
built-in test fixture. This
low-capacitance cable is used, for example, to connect type-874
connected impedance sta n dards or a special
test fixture. Make connections as follows:

a. Remove the ad aptors, if pr esent, from the t est fixture.

b. Plug the single-connector end of the extender cable into the
Digibridge test fixture s o that its blades enter both slots and the cable lies
away from the display panel. Lock the connector with the two captive
thumb screws.

c. Using the branched end of the cable, connect to the DUT with
careful attention to the following color code.

The cable tips are type 874 coaxial connectors, which
mate with a broad line of components and adaptors.

Notice that the 2 wires with red must connect to the same end of the
DUT, through a coaxial tee if the DUT is a 2-terminal device; the 2
wires labeled with black, connect to the other end, similarly. Connect
the outer (shield) contacts to the shield or case of the D U T only if it
is isolated fr om both ends of th e D U T.

EXTENDER CABLE COLOR CODE

RED AND RED: 1+, current driv e to

"high" end of DUT.

RED AND WHITE: P+, potential connection

to same.

BLACK AND BLACK' I-, cur rent return at

DUT "low".

BLACK AN D WHITE: P- , p o t ential

connection to same.

OUTER CONTACTS: G, guard connection

to shield or case.

2.6 EXTERNAL BIAS. Figure 2-3.

WARNING

To minimize electrical shock hazard, limit

bias to 30V.

Bias voltage is present at connectors, test

fixtures and on capacitors under test.

Capacitors remain charged after measurement.
Do NOT leave instrument unattended with bias

applied.

Full bias voltage appears on test lea ds, bias-voltagesource terminals,
and on the leads of the component being measured. Capacitors that have
been charged are dangerous until properly discharged; the user must fo llow
safe procedures to assure discharge. For safety, all personnel operating the
instrument with bias must be aware of the hazards, follow safe procedures,
and never leave the equipment una ttended with bias voltage applied.

2.6.1 Basic Bias Connections.

In order to measure a capacitor with dc bias voltage

applied, connect an external voltage source, as follows:

a. Attach the rem o te test fixtur e or an extender cable as described in

paragraph 2.5. Observe the color coding explained there.

INSTALLATION 2-3

b. Connect a suitable bias voltage source (see below)
in series with the 1+ connection, basically as shown in
the diagram, with the following details.

With the Remote Test Fixture. Disconnect the red coded BNC cable end
from the remote test fixture and connect one end of plain BNC cable there
instead.
Connect the red coded BNC cable end to the negative terminal of the bias
voltage source. Connect the remaining free end of the plain BNC cable to
the positive t erm inal of the bias voltage source. C onnect the DUT to
the test fixture in the usual way.

With 1657-9600 Ex tender Cable (Banana Plugs). Connect the red
banana plug to the negative terminal
of the bias voltage source. Connect a suitable banana
plug patch cord to the positive terminal. We designate
the free end of this patch cord as I++, as shown in the

diagram.

With 1688-9600 Ex tender Cable

("Type 874 Connectors").
Connect the "red and red" cable to t he negative termin al of the bias volta ge
source. Connect a suitable type-874 patch cable to the positive terminal.
We designate the
free end of this patch cable as I++, as shown in the diagram.

c. If either of the extender cables (not the rem ote test fixtu re) is used,
connect the DUT as follows. If capacitance is large (r ange 1), make 2
connections to each capacitor terminal (Kelvin connections). That is, I- and
P- to capacitor negative terminal; P+ and I++ to capacitor positive
terminal.

If the capacitance is smaller (range 2 or 3) the banana plugs can be

stacked or a tee used with type-874 connectors

and a single connection made to each capacitor terminal: I- /P- to the

negative terminal, P+/I++ to the positive.

To make 3-terminal (or 5-termina l) measu remen ts, also connect guard
(see paragraph 2.5) to the guard terminal, shield, case, or groun d of the
capacitor, provided that this is insulated from the 2 main terminals of the
capacitor. Do not connect guard to the case of a capacitor if the case is one
of its 2 main terminals.

2.6.2 Bias Voltage Source Description

The bias voltage source must satisfy several criteria:

1. Supply the desired terminal voltage (dc)

2. Serve as source for charging current.

3. Serve as source and sink for the measuring currents
(ac), which are 45, 0.45, and .0045 mA, peak, for measurements on ranges
1, 2, and 3, resp ectively.

4. Present a low, linear terminal impedance (< < 10 ohms)

at measuring frequency.

If the bias volta ge source is a regulated power supply
with the usual characteristic that it functions properly only as a source, not
a sink, then the following test setup is

recommended. Connect across the power supply a bleeder resistor that
draws dc current at least as great as the peak measuring current (item 3
above). In parallel with the bleeder, connect a 100-pF capacitor. (If the
power supply has exceptiona lly good transi ent response, the capacitor i s
not necessary.)

No single bleeder resistor will suffice for all bias conditions, so it may
be necessary to switch among several. Each resistance must be small
enough to keep the power supply regulator current unid irectional (as
mentioned above) for the smallest bias voltage in its range of usefulness.
Also the resistance and dissipation capacity must be large enough so that
neither the power supply is overloaded nor the resistor itself damaged for
the highest bias voltage in its range of applicat ion.

NOTE

For convenience, a suitable active current sink
can be used in lieu of bleeder resistors.

A discharge circuit is also required. (Do not depend on the above­mentioned bleeder resistor.) A dual discharge circuit is recommended.
Connect a clip lead with a 10-Q resistor in series and another plain clip lead
to the I-/Pjunction. Provide the loos e ends of these with insulated alligator
clips for us e when completing the discha r g e path across th e D U T. For a
recommended procedure, refer to para 3.6.

I f the measurement program warrants the exp ense of a test fixture for
biased-capacitor measurements, its functi on should be equivalent to that of
the circuit described above. It should be equipped with convenient
switching to remove the bias source, discharge through 10 Q, and finally to
short out the capacitor after measurement. For automated test setups, it is
also feasible to precharge the capacit o rs before they are attached t o the test
fixture and to discharge them after they h ave been removed.

CAUTION

To avoid damage t o the instrument, limit the bias voltage t o 30 V,
maximum, in any precharging
bias supply, used as mentioned above.

2.7 ENVIRONMENT.

The Digibridge can be operated in nearly any en vironment that is
comfortable f o r the operator. Keep the instrument and all connections to
the parts under test away from
electromagnetic fields that may interfere with measurements.

Refer to the Specifications at the front of this manual for temperature
and humidity tolerances. To safeguard the instrument during storage or
shipment, use protective packaging. Refer to S ection 5.

2-4 INSTAllATION

OPERATION 3-1

3.1 BASIC PROCEDURE. Figure 3-1.

For initial familiarization, follow this procedure care

fully. For details, refer to later paragraphs in Operation.

a. Before connecting the power cord, slide the linevoltage switch (rear
panel) to the position that corresponds to your power-line voltage. Power must
be nominally either 50 or 60 Hz ac, either 120 or 220 V. (Refer to
specifications at front of this manual.) The 1657-9700 can be run on 50 Hz but
with some loss of accuracy for 120-Hz measurements in high range
extensions. Similarly, the 1657-9800, if run

on 60-Hz power, experiences some extraneous noise in 100Hz

measurements in high range ext ensions.

If the fuse must be replaced, be sure to use a "slow

blow" fuse of the rating shown on the rear pan el.

b. Connect a typical device, whose impedance is to be

measured, as follows. (This device under test is denoted DUT.)

NOTE

Clean the leads of the DUT if th ey are notice
ably dirty, even though the tes t-fixture cont acts
will usually bite through a film of wax to pro
vide adequate connections.

Radial-lead DUT: I nsert the leads into the test.fixture
slots as shown in the photograph, Figure 1-1. For details of wire size a nd
spacing limits, refer to para 3.2.

Axial-lead DUT: Install the test-fixture adaptors, supplied, one in
each slot of th e test f ixtu re, a s shown in th e acc ompan ying figu re. Slid e
the adaptors together or apar t
so the body of the DUT will fit easily between them. Press the DUT down
so that the leads enter the sl ots in the adaptors as far as they g o easily. For
details of wire size and DUT size limits, refer to para 3.2.

NOTE

To remove each adaptor, lift with a gentle tilt
left or right. For a DUT with very short leads
it is important to orient each adaptor so its internal contacts
(which are off center) are close

to the DUT.

Other DUTs, Remote Connections, and Bias.

For connections via extender cables and remote
test fixtures, refer to the installa tion instructions of paragraph 2.5. For
connection of bias voltage and opera ting procedures wit h bias, refer to
paragraphs 2.6 and 3.6. For convenience, the typical color coding used in
extender ca bles is repeat ed below.

Red: I+, current connection to "high" end of DUT. ,

Red & white: P+potential connection to same.
Black: I-, current connection to low endof DUT. .

Black & white: P-, potential connection to same

Black & Green: G, guard connection to shield or case (if isolated
from the preceding terminals). Do not-connect G to the case of a capacitor
if the case serves as (or is connected to) one of its 2 main terminals.

Notice that the 2 red tips must connect to the same end of the DUT. The
terminals with white bands are potential connections; with no bands, current
terminals.

c. Set.the pushbu ttons according to the de sir e d me asur e

ment, as follows:

Power. Depress the POWER button so that it stays in the depressed
position. (To t urn the instrument off, push and release this button so that it
remains in the released position.)

Function. For resistance, depress R. For inductance, depress L/Q. For
capacitance, depress C/D. Be sure that one of these buttons is in the
depressed position.

Frequency. For measurement at 1 kHz, push and release the
FREQUENCY button until the 1-kHz light c omes on. For 120 (100) Hz, pus h
the same button s o that the 120-Hz (100.Hz) light comes on.

Parallel or Series. For series equivalent circuit, push and release the
PARALLEL/SERIES button until the SERIES light comes on. For parallel
equivalent circuit, push thi s button so that the PARALLEL light comes on.
(The choice is significant for lossy capacitors or inductors, not for lowloss
reactive components or non-reactive resistors.) For further explanation, refer
to para 3.5.

Range. Depress the middle (RANGE-2) button first and wat ch the
ADJUST RANGE lights. If the right-pointing arrow is lighted, depress
RANGE button at th e right. If the left-poi nting arrow is light ed, depress
RANGE button at the left. When neither arrow is lighted, the range you have
selected is correct. (Be surc that one of the RANGE buttons is in the
depressed position.) Additional comments on range choices are below.

d. Read the measurement on the main disp lays. The
R LC display is the principa l measurement, complete with decimal point and
units, which are indicated by the light spot behind MΩ, kΩ, Ω, H, mH, nF,
or uF.* The DQ display is D if the C/D FUNCTION button is in, Q if the
L/Q button is in.

e. After any change in DUT or measurement conditions, before looking

at the displays, notice the , ADJUS T RANGE

lights. Interpret them as follows:

Neither light. Correct range. (There are minor exceptions.)

Left Light. Wrong range; try next RANGE button to left.

Right Light. Wrong range; try next RANGE button to

right.

Both Lights. Overrange or invalid display. If FUNCTION is correc t
and RANGE is highest, the measurement is valid bu t because of an
overrange condition, the basic 0.2% accuracy cannot be guaranteed. (If you
switch to RANGE 2, one
of the lights will go out.) If bot h lights are lit on RANGE 2, either the
FUNCTION is inappropriate for the DUT or it is not properly connected.
For more details, refer to para 3.3.

*If the extender cable is used. it may be necessary to correct for its
capacitance.

3-2 OPERATION

3.2 CONNECTION OF THE DUT.

3.2.1 The Integral Test Fixture.

The test fixture provided on the front ledge of the Digi

bridge provides convenient, reliable, guarded 4-terminal connection to

any common radial-lead or axial-lead component.

If the slots of your test fixture have rounded ends, the

slots accommodate wires of any diameter from 0.25 mm (.01 in., AWG

30) to 1 mm (.04 in., AWG 18), spaced from 6 to 98 mm apart (0.23 to 3.9
in.) or equivalent strip conductors. Each "radial" wire must be at least 1 cm
long
(0.4 in.). However, if the slots of your test fixture have square ends, they
will accommodate wires spaced as close as 4 mm (0.16 in.) and each
"radial" wire must be at least
4 mm (0.16 in.) long. The divider between the test slots contains a shield, at
guard potent ial, with its edges exposed. Th e adaptors accomm odate wi res
of any diameter up to 1.5 mm (.06 in., AWG 15). The body of the DUT that
will fit between these adaptors can be 80 mm long and 44 mm diamet er
(3.1x1.7 in.) maximum. Each "axial" wire must be at least 3 mm long (0.12
in.).

For radial-lead parts, remove each adapt or from the test fixture by a
gentle pull upward, made easier by bending the adaptor left or right (never
forward or back). For axial-lead parts, insert the adaptors, one in the left
slot and the oth er
in the right slot of the test fixture, by pushing vertically downward. They
can be slid left and right to match the length of DUT to be measured. Notice
that the contacts inside the adaptor are off center; be sure to orient the
adaptors so the contacts are c lose to the body of the DUT, especially if it
has short or fragile leads.

Insert the DUT so one lead makes connection on the
left side of the test fixture, the other lead on the right side. Insertion and
removal are smooth, easy operations and connections are reliable if leads
are clean and straight.

Be sure to remove any obvious dirt from lead s b efore inserting them.
Be sure the contact pair inside each half of the test fixtu re is held open by a
single item ONLY, whether that is one lea d of an axial-lead DUT or one
adaptor, to obtain true "Kelvin" connections.

3.2.2 Test Fixture Accessories.

An accessory extender cable or adaptor, cable, and remote test fixture,
as described in Table 1-3, is needed
to connect any DUT that is multit erminal, physic ally

large, or otherwise unsuited for the built-in test fixture.
A cable is needed, for example, to connect impedance standards, a
remote test fixture, capacitors to be measured with bias, etc. For

connection to the instrument, refer to paragraph 2.5. For

measurements with bias,
refer to paragraphs 2.6 and 3.6. The color code for the branched end
of each cable is given in paragraph 3.1. To correct for cable
capacitance, refer to paragraph 3.7.

3.3 FUNCTION AND RANGE SELECTIONS.

3.3.1 Function Pushbuttons.

The selection of the principal parameter to be measured is almost self­explanatory. Depress the appropriate FU NCTION button: R, L/Q or C/D to
measure resistance, inductance, or capacitance. The instrument will tolerate,
to some degree, a poor choice of function, but accuracy is thereby reduced.
The readout will i n dicate a completely wrong choic e of function, as
explained below. Notice that the appearance of a device can be misleading.
(For example, a faulty induc tor can be essentially capacit ive or resistiv e;
a component part can be mislab eled or unlabeled.)

If both ADJUST RAN GE lights are on, the RANGE 2 button is in, the
RLC display is blank, and the DUT is properly connected, then the choice
of function is probably wrong. Most likely, if the L/Q button is in, the DUT
is capacitive; or if the C/D button is in, the DUT is inductive.

Observe the DQ display for an indication of poor choice of function
(though tolerable). Large D or small 0 may indicate that the "reactor" being
measured is practically a
resistor at the measuring frequency. If the C/D button is in and the D
reading is between 1 and 10 (or blank, as it will be for D> 10) it is
possible that the DUT is eno,ugh like a resistor to be measured best
with the R button in. Similarly, if the L/Q button is in and the Q reading
is
between zero and 1, it is possible that the DUT is enough like a resistor to
be measured best with the R button in. Notice that when the R button is in,
the DO display is always blank. On the other hand, any D or Q display is
valid, even if the "wrong" function has been selected. (The C or L display
can be blank.)

If the R button is in (a resistor is being m easured) the eas y way to
determine whether the DUT is reactive is to try making C/D and L/Q
measurements. If you obtain a valid C measurement with D < 1, the DUT is
capacitiv e. The smaller this D value, the less accurate the R measurement.
Similarly, if you obtain a valid L measurement with Q > 1, the DUT is
inductive. The larger this Q value the less accurate the R measurement. (See
para 3.4.)

3.3.2 Range Pushbuttons.

Range selecti o n is also nearly self-explanatory. Follow the ADJUST
RANGE lights. The left light means: "Push the next range button to the
left." The right-hand light
means: "Push the next range butt on to the right ." Continue unti l both light s
go out. The instrument will usually display a measurement (at reduced
accuracy) even though the range is not optimum. The following details
about range are best
understood with reference to para 3.4 (particu1arly the RLC basic accuracy
graph).

The RANGE buttons are placed in order of decreasing impedance, 3-2-

1. The "highest" range is therefore Range 1
for C/D; but it is Range 3 for Rand L/Q.

OPERATION 3-3

Each basic range is slightly more than 2 decades wide, from an R LC
display of 01900, with an automatic decimal
point change between the decades, to 19999. (The symbol 0 represents

a blanked zero. Initial zeroes to left of the decimal point are always blanked
out of the RLC display.) Each of the 3 ranges goes beyond its basic range,
with both upper and lower range extensions (shown by lighter lines in the
RLC basic accuracy graph). Several of these extensions are s eldom used
because they overlap "basic" portions of other ranges and because the
operator is alerted to this fact by an ADJUST RANGE light.

Each range in cludes 2 or 3 subranges, distinguished by th e automatic
decimal-point shift. The operator does NOT control them. Subranges are
detailed in Table 3-1. Notice, for example, if you select RANGE 1, C/D, 1
kHz, then there are 2 subranges: 19uF and 999uF. If a series of measure­ments is made with C increasing slowly above 19uF, the automatic
subrange ch ange takes place at 21. But with C decreasing , the change takes
place at 20. This hysteresi s eliminates a possible ca use of flickeri ng of the
display.

The "low" extension of each range goes from 01900 down to 00000,
without any change in decim al point, but wit h r educed accuracy. The
number of digits in this display is always adequate for the specified
accuracy. An y measurement in the low extensio n of either Ran g e 2 or the
highest range causes the appropriate ADJUST RANGE arrow to be lighted.
But there is no such light in the low extension of the lowest range ( because
there is no lower range to select).

the high extension of the highest range, both ADJUST RANGE arrows are
lighted (to indicate a useful "overrange" condition) .

The high extension of the top range for Rand C only, at 120 Hz (100
Hz) only, is a factor of 50, going from 19999, with an automatic d ecimal­point change, up to 99999, and finally to blank, with redu ced accuracy.
(Both ADJUST RANGE arrows are lighted as described above.)

A special case warrants explanation. (This is a minor exception to the

basic procedure of para 3.1.) It is possible

for both ADJUST RANGE lights to be out and yet the RANGE and

FUNCTION buttons to be incorrectly set.

This condition result's from either faulty connection to the DUT or a

numerically small negative Lor C measurement. Sometimes a loose or dirty

connection to the DUT causes

an erratic RLC display. A small negative L or C (wrong function
selected) causes a zero display. In either case, check connections at the test
fixture and try all 3 FUNCTIONS to see which is appropriate, R, L/Q, or
C/D.

The "high" extension of each range is a factor of 5 (with 2 exceptions),
going from 19999 up t o 99999, and finally to blank, without any change in
decimal point, but with reduced accuracy. Any measurement in the high
extension of either the lowest range or Range 2 causes the appropriate
ADJUST RANGE arrow to be lighted. However in

3-4 OPERATION

3.4 ACCURACY.

3.4.1 Graphs. Figures 3-2, 3-3, and 3.4

The following accuracy graphs supplement the statement of accuracy in

the speci fications, at the front of this manual.

Figure 3.2 shows that the R LC basic accuracy of 0.2% is realized over
6 decades of impedance if the correct range
is selected (as indicated by the ADJUST RANG E lights being out).

The reduction of accuracy is shown for all of the "low" and "high" range
extensions. This basic RLC accuracy is valid only for "pure" R. L, or C.
For the effect

Figure 3-2. R L C basic accuracy as a percent of reading. Heavy lines (solid and dotted) represent best
choice of range. Range 2 is dotted. Notice that Land C scales above graph are for 120 Hz (*equally valid for
100 Hz) and the 2 below graph are for 1 kHz. The DQ accuracy factor (right-hand scale) is the multiplier
that, applied to the DQ Basic Accuracy, yields complete DQ accuracy, for range extensions as well as the
basic ranges (where RLC accuracy is 0.2%).

of quadrature impedance, multiply each basic accuracy value by the RLC
accuracy factor; see below.

Figure 3-3 shows the RLC accuracy factor, which depends on D or Q.
For example, suppose a capacitor measured at
1 kHz has C = 400 uF and D = 0.5. The R LC basic accuracy is 0.4% and
the R LC accuracy factor is 1.5. Therefore, the accuracy of the C
measurement is :+/-0.6%. Notice that the
D or Q of a resistor (if significant) can be measured by selecting the C/D or
L/Q FUNCTION.

Figure 3-4 shows the basic DQ accuracy, which is simple function of
D or Q. For D read the lower scale and lower curve. For Q read the upper
scale and upper curve. The basic DQ accuracy is valid only if
measurements are made on one of the 3 basic ranges (where RLC
accuracy
is best). Otherwise, multiply basic DQ accuracy by the DQ accuracy
factor, shown on the right of the "RLC basic accuracy" graph. In the
example of C = 400 uF, D = 0.5, the basic D accuracy is 0.5% and the D
accuracy factor is 2. Therefore, the accuracy of the D measurement is :+/-1%

OPERATION 3-5

The logarit hmic scales on th ese figures make it very easy to apply the
accuracy factors visually. For example, suppose a capacitor is being measured
on range 2, both ADJUST RANGE lights a r e out, and the D display' is about

1. Figure 3-3 shows that the C accuracy factor is about 1/3 of a decade on the
logarithmic scale. On Figure 3-2, find the heavy dotted line (the basic portion
of range 2) and p oint to the basic C accuracy (0.2%) at the left. No w a pply the
C accuracy factor by moving the pointer up about 1/3 of a decade. The pointer
now shows the corrected C accuracy, 0.4%.

3.4.2 Insignificant Digits.

One or more of the digits at the right end of the R LC and/or DQ displays
may be insignificant. This is particularly true at the upper extension of a
range. If th er e are more than one insignificant digits in a display, the least
significant is typically noisy. That is, it will appear to flicker at random over a
range of values and should be ignored.

For example, if you measure a 4-MΩ resistor, the display might ideally

be 4.1234 MΩ; but the one or two final digits might be changing at random.
This flickering is entirely normal. The specified accuracy (+/-0.4%) is the key
to expected performance; in this example, the last 2 digits are insignifi cant
and the last digit is quite unnecess ary. Typically, one would record thi s
measurement as 4.12 +/-.02 MΩ.

3.5 PARALLEL/SERIES AND FREQUENCY SELECTIONS.

3.5.1 General.

The value of th e principal mea surement (R, L, or C) of a certain D U T
depends on which of 2 equivalent circuits is chosen to represent it. (Many
impedance meas uring instrument s provide no choice in the matter, but this
one allows selection.) The more nearly "pure" the resistance or reactance, the
more nearly identical are the "series" and "parallel" values. However, for D
or 0 near unity, the difference is substantial. Also, the principal measurement
often depends on measurement frequency. The more nearly "pure" the
resistance or reactance, the less is this dependence. However, for D or Q near
unity and/or for measuring frequency near the self-resonant frequ enc y of the
DUT, this dependence
is quite substantial. We first give general rules for selection of meas urement
parameters, then some of the theory.

3.5.2 Rules.

Specifications. The manufacturer or principal user of the DUT prob ably
specifies how to measure it. (Usually "ser ies" is specified for C, L, and low
values of R.) Select "parallel" or: "series" and 1 kHz or 120 Hz (100 Hz)
according to the applicable specifications. If there are none known, be sure
to

specify with your results whet her they are "parallel" or "series" and what the
measurement frequency was.

Resistors, below about 1 kΩ: Series, 120 Hz (100 Hz). Usually the

specifications call for dc resistance, so select a low test frequency to
minimize ac losses. Select "series" because the reactive component most
likely to be present in a low-resistance resistor is series inductance, which
has no effect on the measurement of series R. As a quick check on whether
the DUT is nearly pure resi stance, make a separate "parallel" measur ement.
Rp will be larger then Rs. If th e difference is less then 1 %, t hen 0 is less
than 0.1, and the measured Rs is pr obably very close to the dc resist ance.

Resistors, above about 1 kΩ: Parallel, 120 Hz (100 Hz). As

explained above, select a low test frequency. Select "parallel" because the
reactive component most likely to be present in a high-resistance resistor is
shunt capaci tance, which has no effect on the measurement of parallel R. As
a quick check on whether the DUT is nearly pure res istance, make a
separate "series" measurement. If th e difference between Rp and Rs is less
than 1%, then D is greater than 10, and the measured Rp is probably very
close to the dc resistance.

Capacitors below 2 nF: Series, 1 kHz. Unless otherwise specified or for
special reasons, always select "series"
for capacitors and inductors. This has traditionally been standard practice.
Select a high measurement frequency for best accuracy.

Capacitors above 200 uF: Series, 120 Hz (100 Hz). Select "series" for
the reasons given above. Select a low measurement frequency for best
accuracy and to enable measurement of capacitors larger than 1000uF.

Inductors below 2 mH: Series, 1 kHz. Select "series"

as explained above. Select a high measurement frequency for best accuracy.

Inductors above 200 H: Series, 120 Hz (100 Hz). Select "series" as
explained before. Select a low measurement frequency for best accuracy
and to enable measurement of inductors larger than 1000 H.

3.5.3 Series and Parallel Parameters. Figure 3-5.

An impedance that is neither a pure reactance nor a pure resistance can
be represented at any specific frequency by either a ser ies or a parallel
combination of resistance and reactance. Keeping this concept in mind will
be valuable
in operation of the instru ment and interpreting its measurements. The values
of resistance and reactance used in the equivalent circuit depend on whether
a series or parallel combination is used. The equivalent circuits ar e shown in
Figure 3-5. The relationships between the various circ uit elements are as
follows.

3-6 OPERATION

3.5.4 Equivalent Series R for Capacitors.

The total loss of a capacitor can be expressed in several ways, including
D and "ESR." To obtain equivalent series resistance, one can measure
directly (if D is high enough to permit the desired accuracy) or calculate.

Direct Measurement. If, while measuring C, you observe that D is
above 0.1 (or some other limit of your choice, see Figure 3-3), push
FUNCTION button R and select SERIES.

Both C and ESR should be measu red on the same range. If D is below
1, the range s hould be correct for C, even though the ADJUST RAN GE
light comes on whi le you measure ES R. However, if D is above 1, choose
the correct "R" range to obta in ESR; and then r emeasure C on this range.

Calculation. If D is small, it is better to calculate "ESR" as follows: Rs

= D/2πfCs where π = 3.1416. D and Cs are displayed on the front panel.
Frequency f depends on the model of the instrument and the selected
frequency as follows (+/- .01%):
1657-9700: "1 kHz" i s 1020.0 Hz; "120 Hz" is 120.0 Hz. 1657-9800: "1
kHz" is 1000.0 Hz; "100 Hz" is 100.0 Hz.

"Equivalent series resistance" is typically much larger than the "ohmic"
resistance of the wire leads and foils that are physically in series with the
heart of a capacitor. ESR includes also the effect of dielectric loss and is
therefore

dependent on frequency.

3.5.5 Parallel Equivalent Circuits for Inductors.

Even though it is customary to measure series inductance of ind uctors,
there are situations in which the parallel equivalent circui t better represents
the physical device. At low frequencies, the significant loss mechanism is
usually "ohmic" or "copper loss" in the wire and the series ci rcuit is
appropriate. If there is an iron core, at high er frequencies the significant
loss mechanism may be "core loss" (related to eddy currents and hysteresis)
and the parallel equivalent circuit is appropriate. Whether this is true at 1
kHz should be determ ined by an understanding of the DUT, but p r ob ably it
is so if the following is true: th at measurements
of Lp at 1 kHz and a t 120 Hz (100 Hz) are more nearly in agreem ent than
measurements of Ls at the same 2 frequencies.

3.6 BIAS.

To measure a capacitor with bias applied, it is necessary to insert a bias
voltage source in series with the I+ lead to the DUT and to provide a means
of discharging it. Refer to para 2.6 for installation of th e recommended
circuit.

OPERATION 3-7

WARNING

To minimize shock hazard, limit bias to 30 V.
Bias voltage is present at connectors, test

fixtures and on capacitors under test.
Capacitors remain charged after measurement.
Do not leave instrument unattended with bias

applied.

Although sp ecial precautions are not required, we recommend the

following procedure, to assure controlled

conditions for both charging and discharging. capacitors.

a. Set the bias voltage to zero.
b. Attach the DUT, with corr ect polarity.
c. Raise the b ias voltage to the specified value.
d. Allowa specified charging and soaking time.
e. Observe and record the specified measurements

(usually Cs and D).
f. Set the bias voltage source to zero.
g. Connect the 10 -n discharging circuit.
h. After about 2 s, connect the safety short circuit.
i. Remove the DUT and the dischargin g circuits.

3.7 CORRECTION FOR TEST FIXTURE ACCESSORIES.

3.7.1 With the Remote Test Fixture.

The remote test f ixture, cable ass embly, and adaptor (1689-960 0,

-9602, -9601) introduce ab out .001 nF of capacitance in pa rallel with
the DUT, a generally n egligible error. For the b est accuracy, select
PARALLEL, C/D, and range 3; measure the capacitance "Cc" with
the remote test fixture open (no DUT). Then measure a DUT, PARALLEL,
C/D; the RLC display is now
Cc + Cx, where Cx is the capacitance of the DUT. Therefore, subtract the
measured Cc from the R LC display to obtain Cx.

3.7.2 With the 1657-9600 Extender Cable (Banana Plugs).

The 1657-9600 extender cable introduces about .0002 nF of capacitance
in parallel with the DUT, a negligible error. For very high precision, the
following procedure can be used,

determining a correction for measurements of parallel

capacitance.

Because the physical arrangement and spacing of the cable branches and
connectors is significant, a correction should be determined for each
measurement setup. The following procedure applies to connection with a
precision 3-terminal capacitor, GR 1404 or 1413, for example:

a. Install an adaptor, GR 874-Q2, on each of the

two coaxial connectors, Land H, of the capacitor.

b. Connect cable branch G to the ground post of the "low" terminal
adaptor. With a clip lead or plain wire, connect this point to the ground post
of the "high" adaptor.

c. Connect cable branch P- t o th e main post of th e

"low" adaptor and stack I- on top of P-.

d. Similarly, connect P+, with I+ stacked on top of it,

to the main post. of the "high" adaptor.

e. Measure this total capacitance, the sum of the desired

measurement and the cable capacitance, Cx + Cc.

f. Carefully lift the stacked pair of cable tips, I+/P+, from the "high"
adaptor and hold them about 0.5 cm (1/4 in.) above the binding post where
they were connected.
Do NOT rearrange the cab le branches or change their spacing more than is
absolutely necessary to follow these directions. Hold the plastic tips (not the
wires) and touch th e guard (G) circuit firmly with a couple of fingers, to
minimize the

effect of capacitance in your body.

g. Measure the cable capac i tance, Cc.
h. Subtract the result of st ep g from that of step e,

to obtain the desired measurement, Cx.

3.7.3. With the 1688-9600 Extender Cable

("Type 874" Connectors).

The 1688-9600 extender cable introduces no parallel capacitance that can
be resolved on the 1657 Digibridge, if the shielding between "high" and
"low" is maintained consistently. For example, to connect a 3-terminal DUT
having two type 874 connectors, use a type 874 tee for the red and red/white
cables, and another type 874 tee for the black and black/white cables.

3.8 CARE OF DISPLAY PANEL.

Use caution when cleaning the display window, not to scratch it nor to
get clean ing substances into the instrument. Use soft cloth or a ball of
absorbent cotton, moistened with a mild glass cleaner, such as "Windex"
(Drackett Products Co., Cincinnati, Ohio). Do NOT use a paper towel; do
NOT use enough liquid to drip or run.

If it should be necessary to place marks on the window, use paper-based
masking tape (NOT any kind of marking pen, which could be abrasive or
react chemically with the plastic). To mi nimize retent ion of any gummy
residue, remove the tape within a few weeks.

3.8 OPERATION

4.1 INTRODUCTION.

4.2 PRINCIPAL FUNCTIONS.

4-1

4-2

4.1 INTRODUCTION.

4.1.1 General.

This instrument uses an unusual method of measurement, which is quite
different from those used in previous impedance meters or bridges. A
thorough understanding of this method will be helpful in unusual
applications of the instrument. The following paragraph gives a brief overall
descrip. tion outlining the measurement techniqu e to one familiar with
impedance measurement methods. A more detailed description of operation,
specific circuitry, and control signals is given later.

4.1.2 Brief Description of the 1657 Digibridge.

This Digibridge TM uses a new measurement technique, in which a
microprocessor calculates the desired impedance parameters from a series
of 8 voltage measurements.* These
measurements include quadrature (90°) and inverse (180°) vector

components of the voltage across the "unknown" impedance Zx and the
voltage across a standard resistor Rs

carrying the same current as Zx .Each of these measure
ments is meaningless by itself, becaus e t he current through

Zx is not controlled. But the 8 measurements are all made in rapid
sequence with the same phase-sensitive detector
and analog-to-digital c on v er ter. Therefore properly ch osen differen ces
between th ese measurements subtract out f ixed offset errors, and ratios
between th e d ifferences cancel out the valu e of the common current and
the scale factor of the detector-converter.

The phase-sensitive detector uses 4 reference signals, precisely 90°
apart, that have exactly the same frequency as the test signal, but whose
phase relationship to any of the analog voltages (such as the 8 mentioned
above) or currents (such as the current through Zx and Rs) is incidental.
Therefore, no precise analog phase shifter or waveform squaring circuit is
required. Correct phase relationships are maintained by generating test
signal and reference signals from the same high -freq uency source.

There are no calibration adjustments in the Digibridge, thanks to the
measurement techniqu e. The only preci sion

'Patent applied for.

components in this instrument are three standard resistors
and a quartz-crystal stabilized oscillator. There is no reactance
standard. For example, C and D are calculated by the microprocessor
from the set of 8 volta ge measurements an d predetermined va lues of
frequency and the
applicable standard resistance.

The microprocessor also controls the measurement sequence, using
programs in the ROM memory and a few manual selections. The desired
parameters, C and D, Land Q, or R; equivalent circ,.uit, series or parallel;
and frequency, either 120 Hz (100 Hz) or 1 kHz, are selected by front
panel cont rols. There are a lso three manu ally
selected ranges, which have wide overlap. The optimum range for
any measurement is indicated by panel lights.

Each range is 2 decades wide, with reduced-accuracy
extensions both above and below. For example, consider resistance
measurement on Range 1 (F igure 3-2). The 2 decades extend from

02.000 Ω, with an automatic decimal-point shift at 02.100 going up (at

020.00, going down) to 200.00 Ω. The range extensions go as far as
can be displayed wit hout further decimal-point shifting: upwards to

999.99 Ω, downwards to 00.001 Ω. Leading zeroes before the decimal­point (0) are blanked out.

Test frequen cies are withi n 2% of the front-panel indication.
However, for reasons related to rejec tion of power-line-frequency stray
signals that could be picked up by the D UT, thereby causing
measurement errors, the actual frequencies are as follows --accurate to
:+/-.0l% -

catalog number 1657-9700: 1020.0 Hz, 120.00 Hz
catalog number 1657-9800: 1000.0 Hz, 100.00 Hz.

4.1.3 Block Diagram. Figure 4-1.

The block diagram shows the microprocessor (uP) in
the upper right corner connected by data and address buses to digital
circuitry including RAM and ROM memories, status and control latches,
and the front-panel display.

Analog circuitry is shown in the lower part of the diagram, where Zx is
supplied with a test signal at frequency f from a sinewave generator, driven

by a crystal-controlled digital
frequency divider circuit. The front-end amplifier circuit supplies an analog
signal that represents 2 impedances alternately: the internal standard, Rs,
and the DUT, Zx.

THEORY 4-1

4-2 THEORY

4.2.2 Frequency and Time Source. Figure 4-3.

A necessary standard for accuracy is the frequency of the test signal; and
equally important are the generation of 4-phase references for detection and
clocks for the microprocessor. Frequency and timing requirements are
implemented by derivation from a single very accurate oscillator, operating near
25 MHz. Digital dividers and logic circuitry provide the many clocks and
triggers, as well as driving the sine-wave generator described below.

4.2.3 Sine-Wave Generation. Figure 4-4.

Starting with a digital signal at 256 times the selected
test frequency, the sinewave generator provides the test signal that drives a
small but essential current through the DUT.

Binary dividers count down from 256 F, providing 128 F, 64 F, 32 F,... 2F,
F. This set of signals is used to address a read-only memory which contains a
256-step approximation
to a sine function. The ROM output (as an 8-bit binary number) is
converted by a D/A converter to a somewhat "noisy" sine-wave, which is then
smoothed by filtering before its use in the measurement of a DUT.

5.1 CUSTOMERSERVICE..................................................................................................................... 5-1

5.2 INSTRUMENT RETURN.................................................................................................................. 5-1

5.3 REPAIR AND REPLACEMENT OF PLUG-IN BOARDS................................................................. 5-1

5.4 PERFORMANCE VERIFICATION................................................................................................... 5-2

5.5 MINIMUM-PERFORMA NCE STA NDARDS . ................................................................................... 5-2

5.6 DISASSEMBLY AND ACCESS. ......................................................................................................5-9

507 PERIODIC MAINTENANCE............................................................................................................5-11

5.8 TROUBLE ANALYSIS...................................................................................................................... 5-13

WARNING

These servicing instructions are for use by qualified personnel only. To avoid electrical
shock, do not perform any servicing, other than that contained in the operating instructions,
unless you are qualified to do so.

CAUTIONS

For continued protection against fire hazard, replace fuse only with
same type and ratings as shown on rear panel and in parts list.

Service personnel, obs erv e the fol lo wi ng prec autions whenever you
handle a circuit board or integrated circuit in this instrument.

HANDLING PRECAUTIONS

FOR ELECTRONIC DEVICES

SUBJECT TO DAMAGE BY STATIC ELECTRICITY

Place instrument or system component to be serviced,
spare parts in conductive (anti-static) envelopes or carriers, hand tools, etc.
on a work surface defined as follows. The work surface, typically a bench
top, must be conductive and relia bly connected to earth ground thr ou gh a
safety

resistance of approximately 250 kilohms to 500 kilohms.
Also, for personnel safet y, the surface must N OT be metal. (A resis tivity of
30 to 300 kilohms per s quare is s uggested.) A void placi ng tools or electrical
parts on insulators, such as books, paper, rubber pads, plastic bags, or trays.

Ground the frame of any line-powered equipment, test instruments,
lamps, drills, soldering irons, etc., directly to
earth ground. Accordingly, (to avoid shorting out the safety resistance) be sure
that grounded equipment has rubber feet or other means of insulation from the
work surface. The instrument or system component being serviced should be
similarly insulated while grounded through the power

cord ground wire, but must be connected to the work surface before, during,
and after any disassembly or other procedure in which the line cord is
disconnected. (Use a clip

Exclude any hand tools and other items that can generate a static charge.
(Examples of forbidden items are nonconductive plunger-type solder suckers
and rolls of electrical tape.)

Ground yourself reliably, through a resistance, to the wo rk surface ; us e, for
example, a conductive strap or cable with a wrist cuff. The cuff must make
electrical contact directly with your skin; do NOT wear it over clothing.
(Resistance between skin contact and work surface through a commercially
available personnel grounding device is typically in the range of 250 kilohms to
1 megohm.)

If any circuit boar ds or IC packages are to be st ored or transporte d,
enclose them in conductive envel opes and/or' carriers. R emove the items
from such envelopes only with
the above precautions; handl e IC pack a ges wi th out to uchi ng

Avoid circumstances that are likely to produce static charges, such as
wearing clothes of synthetic material, sitting on a plastic-covered or rubber­footed stool (particularl y while wearing wool), combin g yo ur hai r, or mak i ng
extensive erasures. These circumstances are most significant

when the air is dry.

When testing static-sensitive devices, be sure dc power is on before,
during, and after application of test signals. Be sure all pertinent voltages have
been switched off while
boards or components are removed or inserted, whether hard-wired or plug-in.

lead.)

the contact pins.

5-0 SERVICE

5.1 CUSTOMER SERVICE.

Our warranty (at the front of this manual) attests the quality of
materials and workmanship in our products. If
malfunction does occur, our service engineers will assist in any way possible.
If the difficulty cannot be eliminated by use of the following service
instructions, please write or
phone the nearest GenRad service facility (see back page), giving full
information of the trouble and of steps taken to remedy it. Describe the
instrument by name , catalog number, serial number, and 10 (lot) number i f
any. (Refer to
front and rear panels.)

5.2 INSTRUMENT RETURN.

5.2.1 Returned Material Number.

Before returning an instrument to GenRad for service, please ask our
nearest office for a "Returned Material" number. Use of this number in
correspondence and on a tag tied to the instrument will ensure proper
handling and identification. After the initial warranty period, please avoid
unnecessary delay by indicating how payment will be made, i.e., send a
purchase-order number.

5.2.2 Packaging.

To safeguard your instrume nt du ring stora ge an d s hipm en t, plea se use
packaging that is adequate to protect it from damage, ie., equivalent to the
original packaging. Any GenRad field office can advise or provide packing
material
for this purpose. Contract packaging companies in many cities can
provide dependable custom packaging on short notice. Here are two
recommended packagi ng me tho ds.

Rubberized Hair. C over paint ed surfaces o f instrument with protec tive
wrapping paper. Pack instrument s ecurely in strong pr otective corru gated
container (350 Ib/sq in.
bursting test), with 2-in. ru bbe ri ze d hair p ads placed along

all surfaces of the instrument. Insert fillers between pads and container to ensure
a snug fit. Mark the box "Delicate Instrument" and seal with strong tape or metal
bands.

Excelsior. Cover painted surfaces of instrum ent with prot ective wr ap ping
paper. Pack instrument in strong corrugated container (350 Ib/sq in. bursting
test), with a layer of excelsior about 6 in. thick packed firmly against all surfaces

of the instrument. Mark and seal the box as described above.

5.3 REPAIR AND REPLACEMENT OF CIRCUIT BOARDS.

This instruction manual contains sufficient information to guide an

experienced and skillful electronic technician in

fault analysis and the repair of some circuits in this instrument. If a
malfunction is localized to one board (or more) that is not readily repairable, it
can be returned to GenRad for repair. To save time, we recommend th at you
obtain a replacement first, as desc rib ed below, before returning the faul t y board .

Exchanges. For econ om ic al, pr om pt repl acem ent of any etched-circuit boar d,
order an exchange board. Its price is considerably less than that of a new one.
Place the order through your nearest GenRad repair facility. (Refer to the last
page of this manual.) Be sure to request an exchange board and supply the
following information:

1. Instrument description: nam e an d catalog and serial numbers. Refer to
front and rear panels.

2. Part number of board. Refer to the parts lists in this manual. (The number
etched in the foil is generally NOT the part number.)

3. Your purchase order number. This number facilitates billing if the unit is
out of warranty and serves to iden
tify the sh ipment.

To prevent damage to the board, return the defective
board in the packing supplied with the replacement (or equivalent protection).
Please identify the return with the

SERVICE 5-1

1. Instrument description: nam e an d catalog and serial

numbers. Refer to front and rear panels.

2. Part number of board. Refer to the parts lists in this manual. (The

number etched in the foil is generally NOT the part number.)

3. Your purchase order number. This number facilitates billing if the unit is
out of warranty and serves to identify the shipment. The repair facility will
arrange for the prompt delivery of a replacement.

To prevent damage to the board, return the defective board in the packing
supplied with the replacement (or equivalent protection). Please identify the
return with the Return Material number on the tag supplied with the
replacement and ship to the address indicated on the tag.

New Boards. For equally prompt replacement of any etched-circuit boa rd,
and for maximum life expectancy, order a new one. Use the same procedure
as described above, but request a new board. Please return the defective one
to GenRad.

5.4 PERFORMANCE VERIFICATION.

This procedure is recommended for verification that the instrument is
performing normally. No other check isgenerally necessary because this
procedure checks operation of nearly all the circuitry. There are no
calibrations or adjustments that could require resetting; an d the inte rnal stan­dards are very stable. (Howeve r, for a rigo ro us per fo rmance and accuracy
check, refer to para 5.5.) The necessary resistors, capacitors, and inductors
are inexpensive and readily obtained. The most accurate ones available
should be used; tolerances listed are the "best" commonly catalogued. Refer
to Table 5-1.

CAUTION

Be sure the Iine voltage switch, rear panel, is correctly set for your
power Iine voltage.

Verify performance as follows:
a. Set the line voltage switch, connect the power cord,

and depress the POWE R button.

b. Press the PARALLEL/SERIES button, if necessary,

so that the SERIES light stays lit.
c. Press FUNCTION button R.
d. Press the FREQUENCY button, if necessary, so that

the 120 Hz (100 Hz) light stays lit.

e. Press the RANGE 1 button.
f. Install the test fixture adaptors, as described in para 3.2.

Insert the 49.9-0 resistor as the device to be tested or "unknown"
component (DUT).

g. Verify that the displays are within the extremes shown in "check number

1" in Table 5-2, if the resistor value is within the tolerance listed above.

h. Similarly make the other checks indicated in this table. In check number
12, verify that the 5th digit is reasonably stable, as follows. (Notice that the 4th
digit is the least significant one in the readout, for 0.2% accuracy.)

i. In check number 12, the flickering of the 5th digit should stay typically
with in a range of +/-3 counts. For example, if the display is 1.101 X,uF, the "X"
might fIicker between 2 and 8 (or a smaller range). If, for example, "X" is
flickering between 7 and 13, it will of course cause a flickering of the preceding
digit (1.1017 to 1.1023). In such a case, the correct readout is the larger 4-digit
number (1.102) and the 5th digit is acceptably stable.

Tolerances. Acceptable performance of the instrument is bracketed by the
set of display "extremes" in Table 5-2. These are defined as the nominal (ideal)
measurements plusor-minus the sum of the instrument accuracy tolerance and
twice the DUT accuracy tolerance. If the accuracy of your DUT is different from
the recommendation, revise the acceptable "extrem es" accordingly. Notice that
this performance verification is NOT intended to prove the accuracy of the
instrument.

5-2 SERVICE

Insignificant figures. The right-hand digit(s) of the display normally flicker
and change if they are not significant for the specified accuracy of the
instrument. Refer to
para 3.4.

Series DUT. For check number 17 of Table 5.2, the SUT is a series
connection of 0.033 uF and 499 Ω for check 18, 0.033 uF and 49.9 Ω.
For these checks, remove the adaptors from the test fixture. Insert the resistor
in one side and the capacitor in the other side, both slanted so their upper
leads cross each other. Clamp them together with a small alligator clip or
paper clip.

5.5 MINIMUM PERFORMANCE STANDARDS.

5.5.1 General.

This procedure is a more rigorous alternative to the performance
verification described above. Precision stan. dards of impedance are required
for this procedure, which checks the accuracy as well as the overall
performance of the instrument. It will be controlled from the front panel, without
disassembly. Table 5.3 lists the recommended standards and associated
equipment.

Verify that the instrument meets performance specifications as follows.
Notice that the specifications in the front of this manual supercede any that are
tabulated below.

Calibration of Standard. The acceptable RLC readout
(min to max range) may have to be modified if your actual
Zx or Zx accuracy is different from the value tabulated.

For example, if your 1-kΩ standard is actually 1.005 kΩ, known to +/-0.1 %,
then the acceptable readout is 1.005 +/-0.3%, i.e., 1.0020 (min) to 1.0080 (max)
kΩ. (Refer to check E of Table 5-4.)

Insignificant Digits. The right- ha nd digi t( s) of the displ a y norm ally may
flicker and change if they are not significant for the specified accuracy of the
instrument. Refer to

Cable Capacitance. Because the cable adds capacitance in parallel with
the OUT, it is sometimes necessary to obtain a "corrected readout" from the
numerical display on the instrument. Do this for all checks involving small
capacitance (about 1000 pF or less). The equivalent correction for large
inductance (above 30 H at 1 kHz or 3000 H at 120 Hz) is not applicable in the
recommended .inductance check procedure. For capacitance measurement,
obtain the corrected readout by subtracting the cable capacitance from the
visible readout, as described in
para 3.7. Because C is large compared to cable capacitance and D is small, the
simple calculation (subtraction) is applicable whether the measurement is
"parallel" or "series."

Be sure the line voltage switch, rear panel, is correctly set for your
power line voltage.

para 3.4.

CAUTION

SERVICE 5-3

5-4 SERVICE

5.5.2 Resistance Measurement Accuracy.

a. Set the line voltage switch, connect the power
cord, and depress the POWER button. Allow 5 minutes for warm-up
(during which time steps b through f can be done) before accuracy
determination.

b. Press the PARALLEL/SERIES button, if necessary,
so that the SERIES light stays lit.

c. Press the FUNCTION button R.

d. Press the FREQUENCY button, if necessary, so that
the 120 Hz (100 Hz) light stays lit.

e. Press the RANGE 1 button.

f. Connect the 1-Ω standard resistor to the test

fixture, using the extender cable, as described in para 3.1. Connect cable
I+ and I- to the posts on the front of the resistor, and P+ and P- to the
corresponding plugs on the back. (Leave G of the cable unconnected.)

g. Verify that the R LC readout is between the min and max extremes

tabulated for check A in Table 5-4. (Refer to para 5.5.1 for exceptions.)

n. Continue through the checks specified in the table. Connect to the
decade resistor (checks D, E, etc.) as follows: stack cable tips I+ on P+ and
plug them into resistor terminal H; stack I- on P- and plug them into L;
connect G to G.

5.5.3 Capacitance Measurement Accuracy.

Continue as in the resistance accuracy procedure, above,

except as follows:

a. Follow Table 5-5 for details of setup and

performance.

b. Refer to para 3.7, for details of connection to

3-terminal capacitors with coaxial connectors and for the

determ ination of cable capacitance. The corrected readout of capacitance
is the actual display minus the cable capacitance.

CAUTION

Do NOT connect the 1417 capacitor without a
dc blocking capa citor in series with the connection between the
CURRENT H terminal and the Digibridge (I+ terminal).

c. For C standards greater than 1 uF (checks R,
S, T.. .), using the GR 1417 Four-Terminal C Standard, connect a 500­J1F dc blocking capacitor between the CURRENT H terminal and the I+
tip of the extender cable from the Digibridge. (Orient the blocking
capacitor: + to the cable.)

d. For C standards greater than 1 uF, Cx accuracy better than that
indicated in the table can be realized by a calibration of the 1-uF value
and proportional correction of the higher values of the GR 1 417. Typical
accuracy is 0.06% if the GR 1413 is used as the stand ard. (Refer to the
1417 instruction manual for details.) However, for
a Cx accuracy of ab out 0.25%, no calibration is required.

5.5.4 D Measurement Accuracy.

Continue with the accuracy procedure as follows:

a. For DUT, make a series connection of the Rand C
decade boxes, by connection from the high (H) terminal of the
resistance box t o the inner low (L) termin al of the capacitance box.
Stack cable tips I+ and P+ and connect these to the inner high (H)
terminal of the capacitance
box. Similarly stack I- and P- on low (L) of the resistance

box. (Be sure this is not strapped to G.) Connect cable tip G to G of the
resistance box and to the outer terminals of the capacitance box.

b. Follow checks AA... AF in Table 5-6. Notice that the capacitor
settings depend on catalog number of the instrument as well as front­panel frequency settings. Refer to the footnotes in the table.

c. Change the DUT to a parallel combination of Rand C decade
boxes, by changing the high (H) connection of the R box from inoer low
to inner high (H) conn ection of the C box and by connecting low (L) of
the R box to the inner low (L) of the C box.

d. Perform checks BA ...B F (as in step b above), with

C box set to C3 and frequency of 1 kHz (nominal).

e. Change C box setting to C4 and frequency to 120 Hz (100 Hz).

Repeat checks BA. ..BF .

The difference between these 2 measurements is the corrected r eadout.
For each other check, CB, CC,
CD ..., a single measurement is sufficient. Refer to "Method of
Measuremen t" on the calib r ation certifi cate of the inductor.

c. Notice that the low-frequency checks are somewhat limited by the
low Q's of the standard inductors. A Q of 1 or less causes a factor of 2 or
more degradation in the specified accuracy of inductance measurement.

5.6 DISASSEMBLY AND ACCESS.

WARNING

If disassembly or servicing is necessary, it should be
performed only by qualified personnel familiar with the
electrical shock hazards inherent to the high-voltage circuits
inside the cabinet.

5.5.5 Inductance Measurement Accuracy.

Continue as in the resista n ce and capacit ance accuracy

procedures except as follows.

a. Follow Table 5-7 for details of setup and

performance.

b. For check "CA", the GR 1482-B inductor must be measured twice,
i.e., once with a shorting link from center to left "reference" terminals,
once with the link from center to right. (Connect the extender ca ble to the
"connection terminals, NOT the reference" terminals.)

CAUTION

Observe the following prec autions whenever you handle a
circuit board or integrated circuit in this instrument.

(Refer to page 5-0.)

5-6 SERVICE

5.6.1 Disassembly. Figures 5-1 through 5-6.

Use the following procedure for access to replaceable

parts and contact points used in trouble analysis.

a. Disconnect the power cord.
b. Remove the top-cover screws from the rear panel of

the main chassis. See Figure 1-2. Slide the top cover forward
about 6 mm, so that its front corners are unhooked. Lift it directly upward
(Figure 5-1). Reassembly note: 2 screws, 13 mm long.

The next step, removal of display board, is recommended (though not

absolutely necess ary) before removal of t he main circuit board.

c. Remove the 2 support screws, at left and right, that hold the display
board to its brackets. (See Figure 5-8 in para 5.6.2.) Pull the board directly
out of its socket in the main b o ard. Keep the di splay board in its original
(inclined) pl ane un til it is completely free (Figure 5-2) .

SERVICE 5-7

d. Remove the ribbon cable (1657-0200) from power s upply (at V-J1)

and main board (at C-J1). Notice that the connectors are symmetrical and
reversible; and the cable is
extra long, for convenience in servicing.

The next step, removal of the power supply, is NOT related to th e
removal of the main board. Either can be left in place whi Ie the other is
removed.

e. Remove the 4 screws that pass vertically through the corners of the
power supply into the main chassis. Lift the power supply slightly and
move it back carefully while disengaging
the POWER pushbutton extension from its hole in the front
panel (Figure 5-3). Reassembly note: 4 screws,
8 mm long.

Notice that it is possible to remove the main board with the display
board mounted on it , by this procedure: re lease all 8 front push buttons;
remov e screws ABC EGHIJ; lift
rear edge of main board 25 mm and slide it forward 16 mm; lift rear edge to
75 mm (so display board clears cutout in main chassis) and slide the
assembly back until display board reaches spacer; lift rear edge another 15
mm and slide it back until push buttons are free; lift assembly out.

Reassembly note: install screw "I," loosely. Position test fixture as
desired (preferably symmetrical in its opening), before installing screws A,
E, etc.

f. After disconnecting the ribbon cable, provide a convenient
"upsidedown" support by reinstalling the top cover, temporarily. Turn the
instrument, bottom up.

g. Remove 4 screws from the bottom shell, one near
each rubber foot. Slide the bottom shell back (or forward), free of the
main chassis (Figure 5-4). Reassembly notes: Be sure to enfold the pliable
dirt seals at left and right sides of main chassis as you start to slide bottom
shell onto main
chassis; use 4 screws, 8 mm long.

h. Remove 8 screws shown in Figure 5-5 as ABCGHI
(7 mm) and EJ (8 mm). Lift the rear edge of the main board as shown in
Figure 5-6 and slide it back until clear of th e main chassis .

i. For access to the test-fixture contacts, which are on the main board,
remove screws K L and drop the test-fixture guide block off of the test
fixture contacts. Refer to bottom interior view, Figure 5-5.

5-8 SERVICE

Screw K must contact etched-circuit ground. A washer i s supplied

(under screw head) if necessary to do so.

5.6.2 Access. Figures 5-7 and 5-8.

Interior locations that are important for trouble analysis
are shown. Notice the clues to pin numbering; square pads on etched
board are generally pin 1. Conversion items are shown, to make a 1657­9700 function as a 1657-9800, or vice versa. (See para 3.1 for line­frequency consideration.) Conversion involves relocating 2 jumpers and
substitution of precision oscillator U7; refer to parts list, Section 6.
(Thus, with a s p are oscillator , one can obtain test frequenc ies of 100,
120, 1000 Hz.) Notice: if your instrument has separate crystal Yl, it is
changed inst ead of U7; inquire.

The 2 arrows with let ters "A" show approximate area (front right

corner) of analog circuitry. The rest is digital.

SERVICE 5-9

5.6.3 Reference Designations.

Refer to Section 6 for an explanation of these designations.
For example, V- T1 designates transformer number one in the
power supply (V) assembl y. C-U3 i s int egrat ed circui t numb er 3 on th e
C board, which is the analog and control board or the main bo ard.

5.6.4 Removal of Multiple-Pin Packages.

Use caution when rem oving a plug-in integrated-circuit or other
multiple-pin part, not to bend pins nor stress the circu it board. Withdraw
the part straight away from the board. Unles s an IC is known NOT to be a
MaS type, place it immediately on a conductive pad (pins in the pad) or
into a conducti ve envelope.

Do NOT attempt to rem ove a soldered-in IC package without the
proper equipment and skills to do so wi thout damage. If in doubt, return
the board to Ge n Rad.

5.7 PERIODIC MAINTENANCE.

5.7.1 Care of the Test Fixture.

About once a year (more or less depending on usage) the

test fixture should be inspected and cleaned as follows:

a. Remove the C board and expose the text-fixture contacts by

removing its guid e block (part number 1657-2200), as described above.
See Figure 5-5, screws KL.

b. Clean and check the 4 contact strips. Use a card wet with isopropyl
alcohol for cleaning. Hold the board at an angle so that any drip falls away
from the circuit s.

c. If necessary, the contact strips (part number 16861940) ca n be
removed (2 screws apiece). They are supposed
to press against each other, with tiny dielectric spacers preventing

contact. Except at the ends of the gap (where the spacers are) the gap
should be .05 to 0.2 mm (.002 to .008 in.) all along the gap. If accurate
feeler gages are not available, the following criterion can be used: the gap
shou Id be large enough to pass a strip of ordina ry typing paper without
dragging, but narrow enough everywhere (at center and near each end) to
cause some drag as a stack of 3 strips of paper is passed through.

For best results and minimum maintenance effort, the operator must
remove any obvious dirt from leads of DUT's before inserting them into the
test fixture. Its contacts will wipe through a film of wax, but they can
become clogged and ineffectual if the operator is careless about cleanl
iness.

5.7.2 Care of the Display Panel.

Use caution when cleaning the display vyindow, not to scratch it nor to

get cleaning substances into the instrument. Use soft cloth or a ball of

absorbent cotton, moistened with

5-10 SERVICE

a mild glass cleaner, such as "Windex" (Drac kett Products Co., Cincinnati,
Ohio). Do NOT use a paper towel; do NOT use enough liquid to drip or
run.

If it should be necessary to place marks on the window, use paper­based masking tape (NOT any kind of marking pen, which could be
abrasive or react chemically with the plastic). To minimize retention of any
gummy residue, remove t he tape within a few weeks.

5.8 TROUBLE ANAL YSIS.

5.8.1 General.

CAUTION

Only well qualified personnel should attempt trouble
analysis. Be sure power is OFF during disassembly and
setting up for tests. Carefully observe the
MOS HANDLING PRECAUTIONS given in para 5.6.

Resources. Refer to Section 4 for a good understanding of the theory of
operation. The block diagrams and discussion there provide necessary
background, whi ch can generally save ti me in trouble analysis. Refer to
Section 6 for hardware details: circuit layouts, schematic diagrams, and
parts l ists.

Abnormal digi tal signal levels. Most digital signal levels in thi s
instrument are norm ally near zero (logic low), about +3.5 to +5 V (logic
high), or rapidly switching between these states. Failure of a digital source
often produces a dc voltage of about +2 V on a si gnal line. Use high ­impedance p r obes in measuring. Use a scope as well as a voltmeter,
because an average of 2 V may be normal for a digital signal that has a
duty cycle near 50%.

Duplicatedcircuits-. Some circuits, as in the display board for
example, are duplicated several times. The IC's can usually be exchanged
between a faulty circuit and a functional one, to identify a "bad" IC.
Notice, also, that the resistor networks D-Z2 ...D-Z10 are simply compact
packages of 220-Ω resistors. If one resistor is open, it is not necessary to
replace the entire package. Use a 5% resistor.

Circuit board replacement Refer to para 5.3 for recom
mended procedures to obtain replacements.

Telltale symptoms. Scan the following group of symptoms for a
preliminary analysis of trouble and suggestions for more detailed
procedures if applicable.

Display. A perpetually blank digit or decimal point may be caused by a
fault in the directly associated circuit on the display board. (Refer to
comments above.)

Pushbutton. Malfunction of any pushbutton may be caused by a fault in

the switch or in buffer C-U 1 9.

Range. If one range is nonfunctional, check the corresponding switch (C­Sl ...S3), source resistor (R 102. ..), and standard resistor (R69. ..). If range-1
measurements are inaccu rate, also check the inverting amplifier in the

I- circuit, C-U46 pin 6.

D Error. A large D error on range 3 may be caused by faulty "protection"

diodes in the analog front end. Check C-CR12.. .23 (a total of 12 diodes).

D Error. If D measurements are accurate at 1 kHz but erroneous at 120
(100) Hz, fault may be in the test signal filter. Check that C-Q2 is on for low
frequency, off for
1 kHz. If so, check the test signal. (See below. )

Reactance Error. If R measurements are accurate but
C (and L) measurements are not, the test signal source may be at fault. In
checking it, as in the following paragraph, verify that the frequency is within
+/-0.0l% of the specified "actual" frequency. (See front of manual.)

Test Signal. To check performance of the test-signal source, use a scope
to look at the open-circuit signal at the I+ terminal of the test fixture. This
should be an undistorted sine wave at the selected frequency, amplitude about

0.6 V pk-pk (+/-15%) on each range. If this is correct, skip over para 5.8.3.

Analog Front End. To check the entire ana log f r ont end, verif y t hat the
signal at C-U44 pin 8 has the characteristics shown in para 5.8.4, step g,
while the instrument is measuring a DUT. If this is true for all modes
(FREQUENCY, PAR SERIES, R-L/Q-C/D, RANGES), skip to para 5.8.6.
Otherwise, c heck the test signal at the tes t fixture as ou tlined above.

Introduction to Detailed Analysis. The following
trouble ana lysis procedu r es will serve as a guide for localizing a fault to a
circuit area. In some cases, a specific component part can be isolated for
replacement. I n other cases, the problem can be narrowed down only to a
circuit board.

Except for the short-cuts indicated above, follow the procedure strictly in
the order given, doing the principal steps (a, b, c, d,. ..) until a failure is
found. Only then is there an y need for the secondary steps , if any are given at
the point of failure (aa, ab, ac ...).

SERVICE 5-11

5.8.2 Power Supply.

Check the power supply (V assembly) if there is a massive failure
(nothing works) or a s a starting procedur e in any thorough analysis. Refer
to figures 5-8 and 6-10.

NOTE

If a power transistor (U1, U2, or U3) must be replaced, be sure to
spread silicone grease
(like Dow Corning c o mp ound no. 5) on the
surface toward the heat sink. For U 1, coat
both sides of the insulating washer.

a. Check the out put voltages, using a digital voltmeter, with ground

reference at V-J1, pin 9 (ribbon cable unplugged), as follows:

Pin1=+5V.

Pin3=+5V.

Pin4=-8V.

b. Make a check similar to st ep a, with ribbon cable connected, ground
reference at right edge of C board, probing C-J1 from below the board. (This
checks for overload outside the power supply.)

5.8.3 Sinewave Generator. Figure 6-5.

Check the C-board circuits that supply the test signal
to the DUT, as follows: (We proceed backward, toward t he si newave
generator.)

a. Make the following test setup and pushbutton

selections:

DUT: 0.1 uF and 3 kΩ, connected in series.
FREQUENCY: 1 kHz.
PAR SERIES: SERIES.
FUNCTION: C/D.
RANGE: 2.

b. Verify that the signal at test fixture I+ (Figure 6-4) is a

1-kHz sine wave, 0.6 V pk-pk. Use an oscilloscope.

c. Verify that this signal changes amplitude as you

switch ranges, thus:

RANGE 1, 0.68 V pk.pk;
RANGE 3, 20 mV pk-pk.

d. If no fault appears in steps a, b, c, skip to para 5.8.4.

e. Verify that "0.25 V RMS TEST SIGNAL" found at S03 pin 14 is a 1­kHz sine wave, approx 0.6 V pk-pk. (+/-15%). This is the output from U41
pin 6.

f. Check at U41 pin 3 (the pin closest to the front) for
a 1-kHz sine wave, 0.4 V pk-pk.

g. Verify that the output of U 18 found at S03 pin 5 is a 1-kHz sine
wave, 0.8 V pk-pk. (It is rather noisy, as sketched on the schematic diagram,
Figure 6-5.)

h. Remove U 18. Connect a 200-Ω resistor across its socket (XU18)
between pins 2 and 3. (Note: if the resistor leads are about 0.5 mm [0.02 in.]
in diameter,

aa. If trouble is found at step a, check "+5 V" circuit: At outputs of U1

and U2: +5 V dc (regulated).

At WT1 (inputs of U1 and U2): +10.8 V dc.
Across input to diode bridge (yellow-to-yellow): 10 V rms.

ab.Check "-8 V" circuit:

At output of U3: -8 V dc (regulated).
At input (center terminal) of U3: -13.8 V dc.

Across WT7 to WT8: 11.3 V rms.

ac. Check power-line circuit to primary of transformer V-T1.

ca. If this signal is distorted or missing on all ranges, but present at

the right end of R 103, check diode network C-CR 16 ...CR23. If missing
on some ranges(s), check source resistor circuit R101... R103
and switches S1... S3.

fa. Check at U45 pin 10 for a 1-kHz sine wave, 60 m V pk-pk. If this is

verified but step e is not, fault is in U41.

5-12 SERVICE

they will fit the socket directly.) Check at U12 pin 4 for a
1-kHz noisy sine wave, 0.4 V pk-pk. If this is verified but
step g is not, fault is in U18. If neither is verified, reinstall U 18 and
continue.

i. Check that each input to the D/A converter U12 (pins 5. ..12), is a
digital signal, about 4 V pk-pk. Each
of these 8 signa ls should repeat with a period of 1 ms.

If these digital signals a re NOT correct, continue the analysis by

checking the crystal oscillator and divider chain, as follows.

NOTE

Dual specifications of frequency appear below.
The first frequency is correct for 1657-9700
(the 120-H z version). The second is correct
for 1657-9800 (the 100-Hz version). Frequency tolerance is +/-0.01%

ia. If these inputs are verified but step h is not, fault is in

U12 circuit Check at the end of R 16 closest to the rear corner
for +3 V dc; if that is correct, replace U 12. Otherwise, fault

is in associated circuit

j. Make the following test setup. Connect from the scope vertical­channel output to a counter. Be sure to use a lowcapacitance probe at the
scope input, so as not to load the high-impedance circuits being analyzed.

k. Oscillator. Check at U8 pin 14 for a fast digital waveform (see
schematic diagram) of the following frequency: 25.067 or 24.576 :1:0.003
MHz. If correct,
skip to step 1. (This circuit is easily loaded down by test equipment. A more
"tolerant" point is checked in step I.)

l. Check at U8 pin 8 for a square wave, 4 V pk-pk,

2.0889 or 2.0480 MH z. Otherwise, U8 is faulty.

m. Check at U9, pins 1, 9, 8 for pulses (essentially rectangular, as shown
on the schematic diagram), with frequencies as follows:

Pin 1, 1.0445 or 1.0240 MHz.
Pin 9, 522.24 or 512. 00 kHz.

Pin 8, 261.12 or 256. 00 kHz.
Otherwise, U9 is faulty.
n. Check at U10, pins 12,9,5 for similar pulses, as

shown, with frequencies as follows:

Pin 12, 276. or261.12 kHz.
Pin 9, 61.440 or 78.3 kHz.
Pin 5, 30.720 or 26.112 kHz.

Otherwise, U10 is faulty.

NOTE

At pin 12, for the 1657-9700, every 9th square
wave is half the regular width; at pin 9, for
the 1657-9800, every 3rd positive pulse is
only about 1 us wide; therefore the counter
reading may vary somewhat, depending on the
length of its counting interval.

o. Check at U14 pin 2 for sq uare waves, 5 V pk-pk, at 261 .12 or 256.00

kHz.

k. a. If oscillator signal is not verified, remove U8 from its

socket and repeat step k. (Check at U13 pin 13, if convenient.) If
signal is now normal, U8 is faulty. Otherwise, install U8 and
determine whether your instrument has a self-contained oscillator

or a separate crystal Y1.

kb. If your instrument has a separate crystal, remove it and

repeat step k. The correct frequency is approx

31.2 MHz (either 120- or 100-Hz version). If this is verified, Y1 is
faulty. Otherwise, install Y1 and check at U7 pins 2, 3, 11 for

voltages of +4, +3, +4.2V, respectively. If they are correct, U7 is

faulty.

kc. If your instrument has the self-contained

oscillator, failure in steps k and ka indicates the oscillator U7 is

faulty.

oa. lf step 0 is no t confirmed, be sure you have selected 1

kHz on the front panel. Check that FREO SEL (U15 pin 8) is

logic high and FREO SEL (pin 6) is low. (Otherwise check back

through U24, U19, andS8.)

ob. If those checks are confirmed, fault is in the gates U15

pins 4, 10,3 or U14 pin 2.

SERVICE 5-13

p. While monitoring U14 pin 2, push the FREQUENCY pushbutton and
select 120 Hz, (or 100 Hz). Check that
the monitored signal (which should always be 256 times the test frequency) is
now 30720 Hz or 25600 Hz. Again push the FREQUENCY button to select "1
kHz."

q. Check that the outputs of U 16 are square waves,
5 V pk-pk, frequencies as follows (for 1657-9700 or 1657-9800 respect ively):

Pin 12, 130.56 or 128.00 kHz.
Pin 9, 65.28 or 64.00 kHz.
Pin 8,32.64 or 32.00 kHz.

Pin 11, 16.320 or 16.00 kHz.
Otherwise, U 16 is faulty.
r. Check U17 similarly:

Pin 12, 8.160 or 8.000 kHz.

Pin 9, 4.080 or 4.000 kHz.

Pin 8, 2.040 or 2.000 kHz.

Pin 11, 1.0200 or 1.0000 kHz.
Otherwise U17 is faulty.
s. If inputs to the sine rom U 11 are valid (steps j ...r)

but its output is not (steps a.. .i), U11 is faulty; or
possibly (because step i does not check the output code from U 11) U 12 may
be faulty. They can be checked
against their manufacturer's data sh eets.

5.8.4 Front End Amplifiers and Switches. Figure 6-3.

Check the C-board analog ci rcuits that process the measurement signa ls

from the test fixture to the point of A/D conversion, as follows:

a. Verify that there is a normal test signal at the test

fixture. (See para 5.8.1 or para 5.8.3 step b.)

b. Make the setup of para 5.8.3, step a. Measure using a low-capacitance

probe with an oscilloscope. (The frequency counter is not needed.)

c. Check at U43 pin 1 for 1-kHz sine wave, 500 to 620 mV pk-pk. Check

at U43 pin 8 for a similar waveform, 150 mV pk-pk.

d. Check at switch U39 pin 3, using the gate signal SSW1 (U39 pin 5) as
a trigger for your scope. Pin 3 should be a 1-kHz switched sine wave, 500 to
620 mV pk-pk for a few cycles, while SSW1 is logic high.

e. Similarly, check at switch U39 pin 10, using the
gate signal SSW2 (U39 pin 12) as trigger. The signal at
pin 10 should be a switched 1-kHz sine wave, 150to 190 mV pk-pk for a few
cycles, while SSW2 is logic high.

f. Return the scope to automatic triggering. Check at the buffer U44 pin 1
for a 1-kHz sine wave that steps repeatedly between 2 levels. The larger level
should be
4 to 4.5 V pk-pk; the smaller, 1.2 to 1.3 V pk-pk.

g. Check at the integrator U44 pin 8 or the equivalent test point S03 pin 1
for the waveform shown in
Figure 5-9. N o tice that the s taircases each have .17 step s
or 20 steps (for 1657. 9700 and -9800, respectively) for
1 kHz but only 2 steps if you select 120 Hz (100 Hz).

ca. Otherwise, check the associated amplifier U46 pin 6 for a similar

waveform, 160 m V pk-pk. If this is not right, fault mav be in

U46/U42 circuit; if right, fault is in U43

circuitry.

da.lf step d is not confirmed, or if the triggering fails, check SSW1 at

pin 5. It should be a slow rectangular wave, (approx 3 Hz), switching
between approx +5 V and -8 V. Otherwise, check U33 and U24; refer to
para 5.8.5. If SSW1 is correct, U39 is faulty.

ea. Otherwise, or if the triggering fails, check SSW2 at pin 12. It

should be a slow rectangular wave, (approx 3 Hz),

from +5 V to -8 V. Otherwise, check U33 and U24; also refer to
para 5.8.5. If SSW2 is correct, U39 is faulty.

fa. Otherwise, confirm that the input to this stage is

5-14 SERVICE

correct bV checking at S03 pin 3 for sine wave that steps between 2
levels: 500 m V and 150 m V pk-pk. If this is correct, U44 is faulty.

Also, the amplitudes of the staircases depend on the RANGE selected
and the impedance components of the DUT. The chosen conditi o ns
make 1 staircase taller than the other 7; so the waveform can be
"stopped", by careful setting of scope sweep trigger adjustment.
(Preferably, tri gger on the positive s lope, at a low voltage. )

ga. If step g is not verified, check at the switch control terminals

U40 pins 5,6, 12, 13 for the presence of digital

signals with logic high and low levels of +5 V and -8 V.

If all of these signals are present, either U40 or U44 is

faulty; replace both of them. Otherwise, check U33 and U34.

Also refer to para 5.8.5.

h. Check at the comparator output U44 pin 14 or test point S03 pin 2
for CMP, a positive puls e (+5 V) on a
base line about -5 V dc. Otherwise, U44 is faulty.

i. If a nonfun ctional instr ument passes all the preceding checks, i.e., no
fault can be found in the analog circuitry, the fault is liable to be in digital
circuitry.
See below.

5.8.5 Control Signal Checks. Figures 5.10, 5-11.

If there is no staircase waveform at the integra tor output (U44 pin 8),
as described above, the following procedure is recommended to determine
whether the fault is in the digita l control circuitr y.

SERVICE 5-15

5-16 SERVICE

a. Look at the following control signals with a scope

and compare them with the timing diagram:

PBST, at C-U33 pin 10;
PMSR, at U33 pin 12.

If they are normal, skip to step b. If they are inactive, perhaps they
can be stimulated by applying pulses to the power-on reset circuit; see
step aa.

b. Examine each of the following digital feedback

signals and compare it with the timing diagram. If anyone is
questionable, check the circuit from which it is, derived;

F, 2F, and 4F, at U4 pins 2, 4, and 6 (from U17); DMSR, at U4 pin
10 (from PMSR via U33 and U34); DONE, at U25 pin 1 (from RES via
U29 and U35).

Notice that DONE would echo CMP if the latter were provided as
usual, by the integrator and c omparator, U44. Otherwise, DONE echoes
the reset pulse provided in step

""

aa. Provide reset pulses in either of 2 ways. Preferably, set

up a pulse generator as follows:

Source resistance: 50 Ω.
Repetition rate (period): 1 s.

Pulse polarity and duration: positive, 0.5 s.

DC levels: high = 4.5 V; low = 0 V.

Connect from ground to: U6 pin 13.

ab. The alternative method is to short across C5

momentarily (and repeatedly) with a clip lead. Watch the scope
carefully for activation, perhaps for only 1 cycle, of PBST
and/or PMSR, after each application of the short circuit. Notice

that this short must be only momentary and that it must not be

applied while the pulse generator is connected. Find C5 at the

rear edge of the C board, nearest Q1 which is between

U6 and U7.

ac. If PBST and PMSR remain inactive in spite of the

preceding stimulation, the digital control circuitry is at fault:

go to para 5.8.6. Otherwise, proceed to step b, continuing to

use the reset pulses.

SERVICE 5-17

c. If the feedback signals ar e present, look at each of the followi ng
control signals and compare it with th e timing diagram: (The fi rst 4 signals
have logic low and high levels of 0 and +5 V; the last 8 signals, -8 and +5V)
PBST, at U33 pin 10;
PMSR, at U33 pin 12;
PTSW, at U33 pin 8;
RES, at U29 pin 8 (reset, normally only at power turn-on);
SSW1, at U39 pin 5 (from PSSW1, at U33 pin 6);
SSW2, at U39 pin 12 (from PSSW2, at U33 pin 2);
Clock at U34 pin 9 (from 4F, at U29 pin 6);
Reset at U34 pin 1 (from same sources as DONE);
BST, at U40 pin 13 (clocked by 4F, enabled by PBST); BST, at U40 pin 5
(complement of BST);
MSR at U40 pin 6 (clocked by 4F, enabled by PMSR); ISW, at U40 pin 12
(clocked by 4F, enabled byPISW).

If any is abnorm al, trace back to the source of the s ignal, with the help
of the schematic diagram (to check for poor connections or other int erface
problems). If the source is faulty, go to para 5.8.6. If these control signals
are all valid, the fault is probably in the integrator U44 or associated
circuits.

5.8.6 Digital Circuitry.

Display Board. A faulty integrated-circuit package can usually be
identified by interchanging plug-in component parts of the same type
between display channels. Notice that a resistor network need NOT be
replaced as a unit; use ordinary resistors. (See para 5.8.1.)

Recommended Procedure. If careful analysis of a faulty instrument,
using the preceding information, indicates that the trouble is in the digital
circuitry (whether in control, computation, or display decoding), further
analysis is beyond the scope of this manual. Return the faulty board (the C
board, if the fault is digital, an d not
in the display board) or return the instrument for service. Refer to para 5.2
and 5.3.

Special Testing. Because of the very high speed and considerable
complexity of the C-board digital circuitry,
it is impossible to analyze trouble there with ordinary
test equipment. GenRad production and in-factory
service departments make use of fast, versatile automatic test systems (G R
products). Their efficiency and accuracy are important factors in our
recommendation that
digital circuit problems be solved by exchanging boards.

5-18 SERVICE

Parts Lists and Diagrams- Section 6

6.1 GENERAL . . . . . . . . . . . . . . . . .

6.2 REFERENCE DESIGNATIONS . . . . . . . . . .

6.3 DIAGRAMS. . . . . . . . . . . . . . . . .

Figure 6-1. Front view, mechanical parts . . . . . . . . . .

Figure 6-2. Rear view, mechanical parts

Federal Manufacturers Code . . . . . . . . . . . . . .

(Cl

Figure 6-3. Analog and control
Figure 6-4. Analog and control
Figure 6-5. Analog and control
Figure 6-6. Analog and control

Figure 6-7. Display
Figure 6-8. Display
Figure 6-9. Power supply
Figure 6-10. Power supply

CD)

(D) board, 1658-4715, diagram . . . . . . .

board, -4700, front end diagram.

(Cl

board, 16574700, layout

(C)

board, -4700, signal sources diagram

(Cl

board, -4700, digital control diagram

board, 16684715, layout . . . . . . . .

(V) board, 1657-4720 layout . . . . . .

(V) assembly, 1657-4720, diagram . . . .

_ . . . . . . _ . . .

6.1 GENERAL.

This section contains the parts lists, circuit-board layout

drawings and schematic diagrams for the instrument.

(Section 4 contains functional block diagrams. Section 5

contains photographs of the instrument, identifying various

parts.) The heavy lines on schematic diagrams denote the
major signal flow.

Reference designation usage is described below.

U, integrated circuit; WT, wire tie point; X, J, P, or SO,
connector; Y, crystal resonator; Z, filter or network.

Each assembly (typically a circuit board) has its own
sequence of designators which can be identified by using
prefixes, such as A- for the main frame and V- for power
supply. Examples: B-R8 designates B board, resistor 8;
D-WT2 = D board, wire-tie point 2; CR6 on the V schema­tic is a shortened form of designator V-CR6 = V board,

6.2 REFERENCE DESIGNATIONS.

Each electrical component part on an assembly is identi-

diode 6. The instrument may contain A-R 1, B-R 1, C-R 1,
and D-Rl.

fied on equipment and drawings by means of a reference
designator comprised of numbers and letters. Component
types on an assembly are numbered sequentially, the

bers being

preceeded by a letter designation that identifies

num-

the component (R for resistor, C for capacitor, etc.). Some

of the less obvious designators are: DS, lamp; Q, transistor;

6.3 DIAGRAMS.

Generally, each schematic diagram is located on a right-

hand fold-out page for convenience. The associated layout
drawing and parts list are located on the same page, the
facing page, or otherwise nearby.

. .

. . . .

. .

6-l

.

.

6-1

. .

6-1

.

.

6-2

.

.

6-2

. .

6-4

.

.

6-5

. .

6-6

.

. .

6-7

.

. .

6-9

. .

6-10

. .

6-11

. .

6-13

. .

6-13

PARTS & DIAGRAMS 6-1

Mk:L;tlANIC;AL

Item

Description

___--------------------------------------

1

2

Foot (4 required) each: 5260-2051 24655

Display panel ( 120

(or) Display panel

3
4

Switch actuator rod assembly 1657-2810 24655 1657-2810

Adaptor for axial leads (2 supplied)

Set of four for replacements

5

Test fixture upper assembly, with

rounded ends of slots

(includes dross tray 1657-7700
and foamed plasticpad) ?657-7800

Matching test fixture contacts (4 required;

included on 1657-4700 board) each:

5

(alt)

Test fixture upper assembly, with

squared ends of slots

(includes dross tray and pad as above)

Matching test fixture contacts (4 required;

included on 1657-4700 board) each:

6

Item

-_--------------------------------------------

1

2.

3
4
5
6

Push button cap

(8

supplied) 5111-0450

Description

.

Power connector

Jl

Fuse extractor post

Line voltage switch

Cover

Top cover

Rottan

shell 1657-8000

Hz)

(100 Hz)

q

Fl

S2

FRONT

CFigure

-1,,,-,,---,,---------------------c--------

REAR (Figure

_____--_-----------------------------

6-l

1 _

den Rad Part Mftr

1657-7001

1657-7002

1657-5995

'l65j-2200

1686-1940 24655

1689-2000

1689-1015 24655

24655
24655

24655

24655
24655 1657-7700
24655

24655

71590

Mftr Part No.

5260-2051

1657-7001
1657-7002

1657-5995

1657-2200

1657-7800

1686-1940

1689-2000

1689-1015

B-315

WT

6-2)’
GenRad

Part

4240-0210

565+0100

791 o-0832

1657-8120 24655 1657-8120
1657-8060 24655 1657-8060

Mftr Mftr Part No.

24655 4240-0210
75915 342-004
82389 lid-1266

24655 1657-8000

.

FEDERAL SUPPLY CODE

FOR MANUFACTURERS

From Defense Logistics Agency

H4-2 SB

708-42

GSA-FSS

Microf icbe

H4-2

Ref FMC Column

in Parts

Lists

code

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01266

0,261

01295

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01930

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02660

02735

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03636

03877

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04919

05079

05245

06276

05402

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05746

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06743

06796

Co915

06928

06978

07047

07126

07127

07233

07261

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08730

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11983

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13103

13148

13150

13327

13715

13919

14010

14196
14332
14433
14462

14609
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1467.4

147.9
14752

14889

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14636

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17856

16324

Sig”nia,S”nn~ele,CA 64086

18642

New PIad Erl&,webe$m 46392
sce”be.,El Montr.c* 6,731

18677

16736

cQmP”rcr Diode.,S.Feihwn.NJ 07936

18795

C”son.$“nnyvc‘c,CA 94ce5

1891,

D”rent..wnnown.WI $3094

16178

Zem.Mo~,Mn
GE.,Geinesvillt,FL3260,

19209

Eesmn.,Ht,mhil‘,M~ 0,830

18373

193%

Pektmn.,Vienne,VA 22180

CCbrron.,Che;lpa.‘L6~22

19817

19ed.e

LRC E‘cmlf.,f&reehecrk.NY 14845

19701

Electre.,lndecendence,Ks 6730,

20093

Elect I”&.,‘4”,rc” HiII.N, 07974

20754

KMC.,Long “dfey.NJ 07863

2,336

wnir

21684

Re”lhuan..NOrvmcd,MA 02062

Lenox F”s*..wblch”“g.NJ 07060

2,766

8-S

22526

22586

Ektro SPece Febrctrc..Topto”,PA 19662

22753

“ID

Wevet.?k..sen Oieg.,~’ a-*--

23338

. _ ._. __,

23342

23636

Pammor.,8ulin~hlm,CA
lndine Gnr‘ Ehvc.,)(scaby,NJ 08632

24361

Ar.%log ‘3e”icee.,cemb*.MA 02142

24366

Generet Semimnd..TemcdAZ86281

:zz

GE.,Schsnecwdv.NY 12305

24464

GE.SY~~~~~.NY 13201
GE..C‘suc,end.Q~ 44112

24455

EMC

24802

Go” Fled..Cmeor.,.MA 0,742

24655

LenOX F”~‘r.,s.Plpi”‘d3.N, 07080

24759

“zclit*.,8erre‘eY,c* 94710

25008

EG&G.,Sldfo,d.d.MA 0,730

25289

-1

Tri-CWnw

26805

omni 8Pectr*.,We‘tbem.MA 02154

26806

Amerken Zetllecr..Cmta Mera.CA 62626

27014

Nelionel.$mte Cl0ra.l

27545

HentorfJ ““iveRBl8n
HP..WlO Alv7,CA 84304

28480

Hewm” M‘g..K*nilwonh,NJ 07M3

28520

28876

‘MC

28989

nofrmen Elcme..El Mo”te,C*9,734

30043

sdid state DeviCes..L.Mirede,CA 90638
6edmen ‘nn.,Ceder Grwe,NJ 07009

30646

30874

‘8M.,Armonk.NY

30886

Permg MeJnericr..Toledo,OH 43809

3,016

Solid Ste~aScntfc.,MonlSamervi,~~,~~

31514

St.“d‘ord AWd E”gr..Corte Meee,CA 62626

3,814

*Mkgic.,Weke‘iald,MA 0,880

3,66,

TririW.,Pimhrgh,PA

32wl

Jensen..CkiccmIC 60638
Swcrrum Cmtmf..Feirview.P* 16415

33696

33173

GE..Qwe”Ytum,KY 42301

3414,

KQOh‘er..b.Wlbor~,MA 01762

54,66

Semicoa..Cona Meee.CA 62626

34333

Silieon Genrl.,Wntminrtsr.CA 92683
A*“enced Micro Dev‘ces.,s”n”“vek,cA 94oss

34336

Inn‘.,Santa Cke,CA 9605,

E-E

sol~tron Qe”iceI.,J”‘JiW,FL 33468

35923

Ccnrrenre.,~~mr*a~.QVE.CAN
NetiD”Cl L*d.,MO”tre*I.QUE.W\N

36462

‘.4ellov.,lndinew‘i%‘N 46206

37942

Merlin Rc&va‘LJemr.town.Nv ,470,

38443

McGill M‘g..“a,,,e,isx,.,~ 46383

39317

40931

HO”*“Wel‘..Mi”“e*POIil.MN 56408

M”ld,..Chicep,,L see?*

42140
42498

NetiOneL.w.a

433%

New DCDl~r*-H”ett.,Sen~“~~“,Q~ 44870
Norme He‘fmen.,snn‘ord,cT 06904

43931

RCwu*w York,NY 10020

19671

Rev*heOn.,W‘thefn,MA 02154

49968

Mo~k.,Cerro‘lton.TX 76006

50088
50101

GHZ Ow‘see.,S.Chdrmford.MA 0,824

50507

Micro Nc~~~~~.,W~,,CIIP,.MA 0,606
Monse”to..Pelo

60622

6472,

and

61167

AIlor El~rce.,Frenchlown,NJ OS825
Diablo S”ttamr..He”ward.CA 94545

5,663

cenrn Eng.,Sra*e co“rge.PA ,680,

6,642

52648

Pk%ev..sente AWSA 62705

SW

62676
52763
53021

6342,

54294

64297

54715

IndL,Phfle~phie.PA

stetrner Trurh.. c.ezenwic. NY 13035
serverno Eklrc.sDrir(p‘idd.l L 62705
XEi:en..Lathenl.NY (2110

53164

T”rO”.,Milwe”kee.W‘ 5320s
8he‘l~r0ee..Sefr”~NC 27676
ASDC Prec Prod..H”ntcvil‘e,*L 35806
Shure 6r01.,Eu~nef0”,,~ 60202

Men”‘m”*

074io

Imt.,New Hyde

Gemn1..0g‘eeb”.,L 6,346

0,057

8seri~.,New 8ritien.cT 06060

EIRIP.,Nw

Cun,be,‘end,P~ 1,070

Elcfm..HoH”wOod,FL33oz2

I

.~

Kh”lg”.,Cherr” HI‘I.NJ 08034

r

T*..N”nde,NY

MBO”etiO..ROEhe*tC,,NH 03867

,034

-

.____

~ra,MA

*ao.c*

S”rtemLcenton,MA 02021

63,, t

P0rt.w

1,040

R,k,IL

60176

MO,0

14817

CA

95051

I‘.,ROCt” HI‘LCT 06067

1893~6

,623,

02176

9.3304

,a32

CO.30

66289 Swc3”e..North *demr,MA 0,247

Sti-n..Bavport,NY

6777,

58653 S”P0k.r

Thomr a 8etrs.,flieemh.NJ 07207

66730

TRW..CINe*nd,GH 44,17

69876

60398

Torrington..Toning*o”,cT 06790

61007 Townrend.,Breintm.MAO2,~

““ion Cerbidr..Nw Yo,L,NY ,001,

6,637

United Csrr Fat.,Sorton,MA

6,664

63060 “inoreen..C‘ew‘a”d.OH 44104

83743

Wed Le~“erd.,Mt.“ernon.NY 10550

66083 Westinglvme..6loo~,e‘d,N, 0,003

We%~n.,Newerk,NJ 07114

66062

Ac*net CW.,New 8ed‘Wd.MA 02742

70106
70109

*6mr
70417 Chwller.,QetrOit,M‘ 4623,
70485 Arlantie
70563

*mpOritL,““iM
70611 Ark-Los Switch..waartown,M* 02172

70892

Seed Chsin.,6ridg~rf,CT 06605

8elde”.,Chicapo.lL 60644

70903

71126 8ronson.,8wnm Fellr.CT 05403

Cwnbridpa Tb,d.,nk.,Cembridge,.MA 02138

7,279

71294

b”‘b&,C‘i‘l0”

71400

8uecm.nn.,St.L0~b.MQ 63,07

714Y) cTS.,E‘*hnt,‘N 46514
7,468 ce”“0”.,L.n *ngelr.CA 9033,

C‘tn..chicego.lL 64646

7,482
71690

Centr~leb.,uihe”kee,wl 53212

co”ti#,atel Qrbo”.,New YOIWY

7,685

71707 0x0 Coi‘..Prouide”ce.RI 02906
7172s crewenr Bax..Phaehlphia,PA 19134
71744 hiag-3 Min Lemp..Chiceg-a,lL SC640

71786

Cineh.,Chieego.l L 6S24

Der”elwowne”.CA 90241

7,623

Efraomoti~..Willimanris.CT 06226

72136

7*228 Continentel SCrew.,New 6ed‘ord.MA 02742

Nyt,O”ice.,6erke,*”

72266

Oi‘ipht.,8rookl”n.NY 11237

72619

Gelled Inrt.,Newert.NJ 07104

72699

oreke.,ChicemlL 6063,

72766

72794 DNI Fee*e”er..W.‘rlip.NY 11795

Eb”..Phi‘edehlhie,PA 19144

72626

Eketie stop N”t..Union,NJ 07083

72962

E,,O..E,iL.PA 16612

72682
73445

nnleex

cemg EbVc..“erttord,CTOGllo

73559

E‘S0 Rsitmr.,New YorkNY

73690

T‘..*tfleboro.MA 02703

73803

73699 JFD Elctm.,8rw*l”n.NY

73667 GrowPin.,R‘h,e‘ieId,N, 07857

Helneme”” ,Tnm.m.NJ 08602

74193
74199

Quem Nicholr..Chis.7go.l L 6os37

74445 HOIO.KrO~e.,He~ffOrd,cT

74545

““bb&.Str*t‘ord.C

‘n.,urtrial Cndne,.,Chicc@,,L 60618

74861

74868 *mDhenoc..Deob”w:cTo68lo

J0h”so”.,wesec0,MN 55393

74970

76042 ‘RC‘TRWl..8”r‘mgten,lA 5260,

K”rr.Kecch.,Qe”lm.o~ 45401

76376

76382 KukaJ.4, “e,non,NY 1066,

76491

Letr”etws”ctPat.Nv 1179,

76638

Linde”.,Pr0”i~.R,

76616 Littel‘“re..Dn Pleinr.l L 60016

76005 Lord
76149

‘“tellor” E1clrLQetrOif.MI 48204
ble”re”.,Chic@o.‘L 60616

7624,

‘4 CO.,94.PM.MN 65101

7636, 3

76386 Minor R”bber..8lOo”‘i*,d,‘u 0,003

Millen.,‘delden,MA

76487
76545 M”Llk, E‘ctr.,Cfevela”d,QH 44114

76684 NItionel Tube.,Piftehrg,PA

‘3.k Indr.,Cryeral

76864

77132 cm* h*“er..vJetsrb”lv.cT 06720

Petton Me~Guw~Prz,vidsn~e.R I 02905

77147

77165 FeU8e”mW,..S”,eNL,NY 13209
77283 Piirse Rotem R”bber..Trenr.m.NJ 08638

Plett 8rm.Wmrbury.CT 06720

77316

Fwtive LoCkwelhCr..NCwerk,‘u

77336

AMF.,PrinEetOn.lN 47570

77342

77542 Re”-a”wd.Wiron,WI 63703

TRW.,Wmden,NJ 08103

77630

77636 Goners‘ Inrt.6rooWvn.NY 1,211
78189 Shke~hoo‘.,E‘gin,lL 60’120

sigme loa..8,arnr,ee:MA 02184

78277

*free

76426

Smckw*.,St ‘.lcr”s.PA 15857

78486

Ti”nermen.,C‘eveb”d,oH

78553

78711 TelephOniCt.,H”“,i”g1Dn.NY 1,743

RC*.,Her,iron.N, 07029
wukier KohinoDr.,New YOrk*NY ,110,

76136

Weet.?,” Rubber.,Goehen.‘N 45525

79497

Wiremo‘d.,nert‘ord,C

79726

Conrinc”r*l Wirt..Phitrdelpilhia.PA ,910,

79727

Ph!lor” Co”tro,s.,Fa”k‘ort,lN ,604,
Zmrick.,Mr KiYO.NY 10649
Tchronix..Bsevert~n,o~ 97005
Pmtolc Fe~te”cr.,Tdedo.OH 43606
Wckerr.,s: LO”ie.MQ 63165
Lembde..Melville,NY 11746

80103

60183 SPreq”e.,N.Adam.MA 01247
80211 Motomle..Fnntlm
8026, Fwnicn.,Cincinnsti.QH 46232

SlmdCd

80258
80294

So”rn$ Labr..RibxeidC,CA 62606
S”lwni*..Ncw Yc.,k,NY

Air Piltrr..Milwaukee,WI 63218

8043,

Hemmpr,“nd..New YO,k,NY

80663

8eckne” ‘nrLF”llrRm.CA 92834

80140

TRW

80766

Yen”‘e$t”nr

1,705

“.‘“e..-iw.,“,PA

a Weff‘eke..Elkkert.‘N 46514

‘“die

R”bber.,Chicqo,‘L 60607

Cit”,N, 0,087

FLl,ge.“A 24422

Htm,

07922

ElcIrCI.,HiCkeJille.NY 11531

,,2,9

ca,,o

06497

02905

M‘g..Eric.PA (6612

o*,.a

LeWL

6001.4

smr..st

Me~*.PA ,586,

w,,o

PLIL

6013,

0iL.L*‘0”*t,*,‘N

Remee”..st L0”i%‘.40 63166

47902

loo,,

,oo,o

,630,

Cod.

80894
81030
8,073
8,143
81312
81349
8,360

8,(83
8,741
6183,

81840

8,860
82219

82227
82273

pvit*creft.,c‘lice~.I

82389
82667

82647

82807

82877

8290,

830(13

83014

63033

83058

83166

63266

83330

83361
83667

83664

83740
83766
63781

8441,

84836
64970
84971

8Go4
84420
86677
se84

E

88140
88204

88216
88419

86627
66266

z

89870

So201

90303

90634

Weeciy)h0”~..60*t.n.M* 0211s

90750
90952

6,032

cen”on.,seIem.MA 01970

91146

9lZlO

Johe”eon..8omton.NJ 07005

91293

91417

*wt

91x)6

ChB”d*,..W~he~‘ie,*.CT 06103

91598
91637
6,662

General

91719

‘Grip Elctrcr..T”eteha,NY 11223

6,836
6,616

MaDhkirto Tcd..H”*con,NY 12534
~o”tyw(lll..fr0el)0n.lL61032

91923

ElccVJ Inr”L.W~dride.NY 11377

62616

Edgerm” GFrlne*“ix~C”..8OStO”,M* 02

62678

IMC MlpnetiCI.,WeTtD”r”,NY 1,591

62702

Ampcx..Rcdwood City.CA 94063

92739

H”dlO” LemP.,Kee,“y.N, 07032

92966

Svlvenia.,Woburo.MA O,SO,

93332

*mer Eletm Let.s..Lanrdnls,PA 19445

63346

‘WC M‘p..Rem3ev,P* ,667,

93618

Cremor..New YcJ,k.NY ,0013

63916

Revtheo”.,Q”inc”,M”

94144

Wagner EIctrc.

94154

weaton.,ArChi~ld.PA 18403

6427,

TOI

64322

DiGson.,C)k~eg~.‘L 60616

94589

‘vtw~r~‘f.,Chi~o,l
Ark

zz

Gerde.,Cumberland.R‘ 02864

1;:

Qucliry Cwnp.$t Mur”r,P* ,585,

95146

*‘co Eletrer..Lewrence,MA 0,843
conrincn*el COnn..Wwdside,NY 1,377

95236

“itnmon..Srid~wt,CT

95276

Gordor.,8loo&ld.N,

96346

MeIhodc.;RO‘ling

96354

*mar 8wse..Torrin~

95784

95987

Weckeecn..Chissgo,l L 60646
AerOMX Hi Q..0‘0.“.NY

96095

Micr~weve Auec..Surliamon.MA 01801

96341

Mi,iMr”SWn.3er*r

96906

Ldl?+rxer SwiMu&%dIoCk.CT 0628,

97918

98291

SeelEStrO..M.~erO”Ce*.NY 10544
com~er..8”rlinseme.c* 94010

98474

No”h Hillr..Glen Cove,NY 1,542

98821

PrOtKdve Cbn”rer..6”“*‘0,NY 14207

99017

‘.+%“.C..F,“~hing.NY , ,358

99117

“er*n.,Rlo

993,3

*1ke..Wi”Ches,*r,M* 01880

99378

99soo

oeie”*n:E.A”rore,NY 14052
Rmbtandr..8onw,MA 02118

99934

ce”treleb.,Milwe”kee.w~ 53201

93942

M*n”‘ect”“,

Pure cerLvn..st wary%PA ,685,
‘nt’l Inrt.,Orenge.CT 06477
Gm”hill..LeGrengc.tL 60626
Irolantite.Stir“ng,NJ 07680

Wi”*ener..oakuilk.Cr 00779

Militery splEaice1i.m.

hint

*mw+Jcw Smcifioetirme

‘“t’l

Rnri‘ier.,El s+“ndo.CA 90246

ChiigD Lc&.,Chiccgo.lL 6C641

FiltrO”.,FI”*hing,NY 1,364
Ledex..De”ton.O” 45402
Barr” wrqht.,wetenown,Mn 02172

8”Ivc”ie.,ErnLori”tn.PA 15a34

No.*mer.Philipe..ChnhlR.CT co410

r‘ewm & ModeL,L.POrI.‘N 46350

IN

Reeve* Hdhcn.,Cerfi*le,P* 17013
MetB‘r& Con”olhkr‘rboro.M* 02703

Reeietor.,Miiwe~kee,Wf 63204

Milwaukee

ROlrO”..WWdllOCk,NY 12498

‘N

tenere~ ~~net..“e~~.reie~.~~ 46383

ve,0.,Ga,k4”4,TX 75040
HanweWkentie.CA 62870
Mei~ne,.,Mt Carme,.“. 62663
car, Fatener..cembribpe.MA 02142
wcfow Eng..SPringfie‘d.NJ 07081
PerbrSeel..Culver CitvCA 90231
li.H.Snli*.,8r00k‘“n,NY 11207

&bide. New Y0rt.N; ,001,

union

Eylr&Quhc".MA 02171

Men

Naiomef Elcws..Gsneva.lL 60134
TRW.,Q@lPb,N869153

Mnel*..cembri~,MA

Lehigh

S1r~Te~ie".,8IW"ingtO".lN
TA M‘g.,Lor Angela,CA 90033

Ke~~.,.,F‘ushinp,NY 1,362
PeYron ceecen.,G","ee,,L 6003,
Prec Mnsl Pmd.,Stonehem,MA 02,80
RCA.,ncrriron.NJ 07029
REC.,NW Rochelle.NY ,080,
Cord Elctrcl.,8*ok‘"n,NY 1,222
Cutler Hemmsr..Linsoln.lL 62656

GTE

Sv‘venia..lprwinh.MA 01938

Wt Semw.,T,onten.N, 08807

Gould

Dubilier.,Fugu*v Verine.NC 27626

Cornell

K&G M‘r..New Ywk,NY
Porter & Brum~iefd..Princaton.lN 4767,
Holfcer WbOt..8OetO”,M* 02119
United Tran*‘ormer.,C~iceg~.IL
serahirr Tr~*‘or~cr..Kent.CT06757
Mauor” cep.,l”dirMPOlie,‘N 46206
MeIIOr” 8er..Terr”tOwn,NY 1059,
Gulron Inds..Mew~hen,NJ 08840

Hwdwerc PrOd..Red*inp,PA 19602
Co”tinentel

win.,vor~P*
Gerb.er..,.,b‘,ewske,lN

He,rir..Melbo”,“e,FL 3260,

6roc.,*~tleborO,MA 02703

aste

5et&.,col”mb”;,rE

Elco..Willow Grwe.PA 19030

Intr..Dallar.TX 76220

Ihi

Labr..mlnchnter,NH 03102

Ind.,8rooklim.NH 03033

A,W.CA 94303

L SW30

02140

47401

1,405

4864

68601

nmm

ng**on,NJ 07039

L 60630

06601

P”-

Y-*-

,‘l,60

-

1116

S-4 PARTS & DIAGRAMS