Keithley 7999-4 Service manual

Model 7999-4

Microwa v e Switch

Instruction Manual

Contains Operating and Servicing Information

WARRANTY

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

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

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

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

LIMITATION OF WARRANTY

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

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

NEITHER KEITHLEY INSTRUMENTS, INC. NOR ANY OF ITS EMPLOYEES SHALL BE LIABLE FOR ANY DIRECT,
INDIRECT, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OF ITS INSTRU­MENTS AND SOFTWARE EVEN IF KEITHLEY INSTRUMENTS, INC., HAS BEEN ADVISED IN ADVANCE OF THE POS­SIBILITY OF SUCH DAMAGES. SUCH EXCLUDED DAMAGES SHALL INCLUDE, B UT ARE NOT LIMITED TO: COSTS
OF REMOVAL AND INSTALLATION, LOSSES SUSTAINED AS THE RESULT OF INJURY TO ANY PERSON, OR DAM­AGE TO PR OPERTY .

Keithley Instruments, Inc. • 28775 Aurora Road • Cleveland, OH 44139 • 440-248-0400 • Fax: [phone] • http://www.keithley.com

BELGIUM: Keithley Instruments B.V. Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02/363 00 40 • Fax: [phone]
CHINA: Keithley Instruments China Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-62022886 • Fax: [phone]
FRANCE: Keithley Instruments Sarl B.P. 60 • 3, allée des Garays • 91122 Palaiseau Cédex • 01 64 53 20 20 • Fax: [phone]
GERMANY: Keithley Instruments GmbH Landsberger Strasse 65 • D-82110 Germering • 089/84 93 07-40 • Fax: [phone]
GREAT BRITAIN: Keithley Instruments Ltd
INDIA: Keithley Instruments GmbH Flat 2B, WILOCRISSA • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
ITALY: Keithley Instruments s.r.l. Viale S. Gimignano, 38 • 20146 Milano • 02/48 30 30 08 • Fax: [phone]
NETHERLANDS: Keithley Instruments B.V. Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
SWITZERLAND: Keithley Instruments SA Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]
TAIWAN: Keithley Instruments Taiwan 1 Fl. 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3572-9077• Fax: [phone]

The Minster • 58 Portman Road • Reading, Berkshire RG30 1EA • 0118-9 57 56 66 • Fax: [phone]

6/99

Model 7999-4 SPDT Microwave RS-232 Switch

Instruction Manual

©1999, Keithley Instruments, Inc.

All rights reserved.

Cleveland, Ohio, U.S.A.

Second Printing, December 1999

Document Number: 7999-4-901-01 Rev. B

Manual Print History

The print history shown below lists the printing dates of all Revisions and Addenda created
for this manual. The Revision Le vel letter increases alphabetically as the manual under goes sub­sequent updates. Addenda, which are released between Revisions, contain important change in­formation that the user should incorporate immediately into the manual. Addenda are numbered
sequentially . When a new Re vision is created, all Addenda associated with the previous Re vision
of the manual are incorporated into the new Revision of the manual. Each ne w Revision includes
a revised copy of this print history page.

Revision A (Document Number 7999-4-901-01).................................................... September 1999

Revision B (Document Number 7999-4-901-01)..................................................... December 1999

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

Safety Precautions

The following safety precautions should be observed before using this product and any associated instrumen­tation. Although some instruments and accessories would normally be used with non-hazardous v oltages, there
are situations where hazardous conditions may be present.

This product is intended for use by qualified personnel who recognize shock hazards and are familiar with the
safety precautions required to avoid possible injury. Read the operating information carefully before using the
product.

The types of product users are:

Responsible body is the individual or group responsible for the use and maintenance of equipment, for ensuring

that the equipment is operated within its specifications and operating limits, and for ensuring that operators are
adequately trained.

Operators use the product for its intended function. They must be trained in electrical safety procedures and

proper use of the instrument. They must be protected from electric shock and contact with hazardous live circuits.

Maintenance personnel perform routine procedures on the product to keep it operating, for example, setting

the line voltage or replacing consumable materials. Maintenance procedures are described in the manual. The
procedures explicitly state if the operator may perform them. Otherwise, they should be performed only by ser­vice personnel.

Service personnel are trained to work on live circuits, and perform safe installations and repairs of products.

Only properly trained service personnel may perform installation and service procedures.
Exercise extreme caution when a shock hazard is present. Lethal voltage may be present on cable connector

jacks or test fixtures. The American National Standards Institute (ANSI) states that a shock hazard e xists when
voltage levels greater than 30V RMS, 42.4V peak, or 60VDC are present. A good safety practice is to expect

that hazardous voltage is present in any unknown circuit before measuring.

Users of this product must be protected from electric shock at all times. The responsible body must ensure that
users are prevented access and/or insulated from every connection point. In some cases, connections must be
exposed to potential human contact. Product users in these circumstances must be trained to protect themselves
from the risk of electric shock. If the circuit is capable of operating at or above 1000 volts, no conductive part

of the circuit may be exposed.

As described in the International Electrotechnical Commission (IEC) Standard IEC 664, digital multimeter
measuring circuits (e.g., Keithley Models 175A, 199, 2000, 2001, 2002, and 2010) are Installation Category II.
All other instruments’ signal terminals are Installation Category I and must not be connected to mains.

Do not connect switching cards directly to unlimited power circuits. They are intended to be used with imped­ance limited sources. NEVER connect switching cards directly to AC mains. When connecting sources to
switching cards, install protective devices to limit fault current and voltage to the card.

Before operating an instrument, make sure the line cord is connected to a properly grounded power receptacle.
Inspect the connecting cables, test leads, and jumpers for possible wear, cracks, or breaks before each use.

For maximum safety, do not touch the product, test cables, or any other instruments while power is applied to
the circuit under test. ALWAYS remove power from the entire test system and discharge any capacitors before:
connecting or disconnecting cables or jumpers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.

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

The instrument and accessories must be used in accordance with its specifications and operating instructions or
the safety of the equipment may be impaired.

Do not exceed the maximum signal levels of the instruments and accessories, as defined in the specifications
and operating information, and as shown on the instrument or test fixture panels, or switching card.

When fuses are used in a product, replace with same type and rating for continued protection against fire hazard.
Chassis connections must only be used as shield connections for measuring circuits, NOT as safety earth ground

connections.
If you are using a test fixture, keep the lid closed while power is applied to the device under test. Safe operation

requires the use of a lid interlock.

If a screw is present, connect it to safety earth ground using the wire recommended in the user
documentation.

!

The symbol on an instrument indicates that the user should refer to the operating instructions located in
the manual.

The symbol on an instrument shows that it can source or measure 1000 volts or more, including the com­bined effect of normal and common mode voltages. Use standard safety precautions to avoid personal contact
with these voltages.

The WARNING heading in a manual explains dangers that might result in personal injury or death. Always
read the associated information very carefully before performing the indicated procedure.

The CAUTION heading in a manual explains hazards that could damage the instrument. Such damage may
invalidate the warranty.

Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and all test cables.

To maintain protection from electric shock and fire, replacement components in mains circuits, including the
power transformer, test leads, and input jacks, must be purchased from Keithley Instruments. Standard fuses,
with applicable national safety approvals, may be used if the rating and type are the same. Other components
that are not safety related may be purchased from other suppliers as long as they are equivalent to the original
component. (Note that selected parts should be purchased only through Keithley Instruments to maintain accu­racy and functionality of the product.) If you are unsure about the applicability of a replacement component,
call a Keithley Instruments office for information.

T o clean an instrument, use a damp cloth or mild, water based cleaner . Clean the e xterior of the instrument only .
Do not apply cleaner directly to the instrument or allow liquids to enter or spill on the instrument. Products that
consist of a circuit board with no case or chassis (e.g., data acquisition board for installation into a computer)
should never require cleaning if handled according to instructions. If the board becomes contaminated and op­eration is affected, the board should be returned to the factory for proper cleaning/servicing.

Rev. 2/99

SBG 8/31/99

7999-4 Microwave SPDT RS-232 Switch

CONTACT CONFIGURATION: Single Pole Double Throw.
CONNECTOR TYPE: 3-SMA type connectors (COMMON, NO, NC).
MAXIMUM SIGNAL: 120W 3GHz (VSWR 1.15 or less), CAT I.
CONTACT RESISTANCE: 0.1Ω max.
CONTACT LIFE: Mechanical: 5 × 10

6

(at 180cpm).

Electrical: 5 × 10

6

(3GHz, 50Ω, VSWR 1.2 at 20cpm).

MAXIMUM COMMON MODE: 42V peak, any terminal to earth.
ACTUATION TIME: 25ms.
RELAY CHARACTERISTICS (50Ω):

To 1– 4– 8– 12.4–

Frequency 1GHz 4GHz 8GHz 12.4GHz 18GHz

VSWR (max) 1.1 1.15 1.25 1.35 1.5
Insertion Loss

(dB max.) 0.2 0.2 0.3 0.4 0.5
Isolation

(dB min.) 85 80 70 65 60

GENERAL

INTERFACE: RS-232 control (9600 baud, 8 data, 1 stop). Response

terminator selectable (CR, LF, CRLF, LFCR).

INDICATORS: Power, relay position status.
ENVIRONMENT: Operating: 0° to 40°C, up to 35°C <80% RH.

Storage: –25° to 65°C.

EMC: Conforms with European Union Directive 89/336/EEC, FCC

part 15 class B.

SAFETY: Conforms with European Union Directive 73/23/EEC.
DIMENSIONS: 109mm long × 112mm wide × 59mm deep (4.3˝ ×

4.4˝ × 2.3˝).

ACCESSORIES SUPPLIED: AC/DC power adapter with line cord,

user and service manual.

T able of Contents

1 General Information

Introduction ................................................................................ 1-2

Feature overview ........................................................................ 1-2

Warranty information ................................................................. 1-2

Manual addenda ......................................................................... 1-2

Safety symbols and terms .......................................................... 1-3

Specifications ............................................................................. 1-3

Unpacking and inspection .......................................................... 1-3

Inspection for damage ......................................................... 1-3

Handling precautions .......................................................... 1-3

Shipment contents ............................................................... 1-4

Instruction manual .............................................................. 1-4

Repacking for shipment ...................................................... 1-4

Connections ................................................................................ 1-4

2 Connections

Introduction ................................................................................ 2-2

Handling precautions ................................................................. 2-2

Configuration ............................................................................. 2-2

Layout ................................................................................. 2-2

Simplified schematic ........................................................... 2-4

Connections ................................................................................ 2-5

RS-232 Connection ............................................................. 2-5

SMA connectors .................................................................. 2-6

Power connector .................................................................. 2-6

3 Operation

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

Maximum signal considerations ................................................ 3-2

Toggle relay state switch ............................................................ 3-2

Operation (RS-232) .................................................................... 3-3

Sending and receiving data ................................................. 3-3

Termination characters ........................................................ 3-3

RS-232 Commands ............................................................. 3-5

Switching considerations ........................................................... 3-6

Connector integrity ............................................................. 3-6

Voltage standing wave ratio ................................................ 3-6

Path isolation ....................................................................... 3-6

Insertion loss ....................................................................... 3-7

RFI/EMI .............................................................................. 3-7

4 Service Information

Introduction ................................................................................ 4-2

Handling and cleaning precautions ............................................ 4-2

Handling precautions ........................................................... 4-2

Card and connector cleaning ............................................... 4-2

Performance verification ............................................................. 4-3

Environmental conditions .................................................... 4-3

Recommended equipment ................................................... 4-3

Channel resistance tests ....................................................... 4-3

Replacing components ................................................................ 4-5

Replacement parts ............................................................... 4-5

Replacement precautions ..................................................... 4-5

Soldering considerations ..................................................... 4-5

Disassembly ........................................................................ 4-5

5 Replaceable Parts

Introduction ................................................................................ 5-2

Parts list ...................................................................................... 5-2

Ordering information .................................................................. 5-2

Factory service ............................................................................ 5-2

Component layout ...................................................................... 5-3

List of Illustrations

2 Connections

Figure 2-1 General layout..........................................................................2-3

Figure 2-2 Simplified schematic................................................................2-4

Figure 2-3 RS-232 interface connector .....................................................2-5

3 Operation

Figure 3-1 Toggle relay state switch..........................................................3-2

Figure 3-2 Jumper location........................................................................3-4

4 Service Information

Figure 4-1 Channel resistance test connections.........................................4-4

List of T ables

2 Connections

Table 2-1 RS-232 connector terminals.....................................................2-5

3 Operation

Table 3-1 Jumper positions—termination characters...............................3-3

Table 3-2 Command set............................................................................3-5

4 Service Information

Table 4-1 Recommended verification equipment.....................................4-3

5 Replaceable Parts

Table 5-1 Parts list—electronic components............................................5-3

Table 5-2 Parts list—mechanical parts.....................................................5-4

1

General Information

1-2 General Information

Introduction

This section contains general information about the Model 7999-4 Microwa ve SPDT switch.
The information is organized as follows:

• Feature overview

• Warranty information

• Manual addenda

• Safety symbols and terms

• Specifications

• Unpacking and inspection

• Connections

If you have any questions after reviewing this information, please contact your local
Keithley representative or call one of our Applications Engineers at 1-800-348-3735 (U.S. and
Canada only). Worldwide phone numbers are listed at the front of this manual.

Feature overview

The Model 7999-4 is a single channel Microwave SPDT switch with the following features:

• SMA connectors

• RS-232 relay control

• +12V DC power connections

• Operating range from DC to 18GHZ

W arranty information

Warranty information is located at the front of this instruction manual. Should your
Model 7999-4 require warranty service, contact the Keithley representativ e or authorized repair
facility in your area for further information. When returning the switch for repair, be sure to fill
out and include the service form at the back of this manual to provide the repair facility with
the necessary information.

Manual addenda

Any improvements or changes concerning the switch or manual will be explained in an
addendum included with the manual. Be sure to note these changes and incorporate them into
the manual.

General Information 1-3

Safety symbols and terms

The following symbols and terms may be found on the switch or used in this manual.

!

The symbol indicates that the user should refer to the operating instructions located in

the manual.

The

symbol

safety precautions to avoid personal contact with these voltages.

The

WARNING heading used in this manual explains dangers that might result in personal

injury or death. Always read the associated information very carefully before performing the
indicated procedure.

The

CAUTION heading used in this manual explains hazards that could damage the switch.

Such damage may invalidate the warranty.

shows that high voltage may be present on the terminal(s). Use standard

Specifications

Full Model 7999-4 specifications are included at the front of this manual.

Unpacking and inspection

Inspection for damage

The Model 7999-4 is packaged in a re-sealable, anti-static bag to protect it from damage due
to static discharge and from contamination that could degrade its performance. Before remov­ing the switch from the bag, observe the precautions on handling discussed below.

Handling precautions

• Always grasp the switch by the covers. Do not touch board surfaces or components.

• After removing the switch from its anti-static bag, inspect it for any obvious signs of
physical damage. Report any such damage to the shipping agent immediately.

• When the switch is not installed and connected, keep the switch in its anti-static bag,
and store it in the original packing carton.

1-4 General Information

Shipment contents

The following items are included with every Model 7999-4 order:

• Model 7999-4 Microwave SPDT Switch

• PS-57A Power Supply Module (AC/DC converter 100-240VAC to 12VDC) / IEC AC
inlet

• Model 7999-4 Instruction Manual (this manual)

• Additional accessories as ordered

Instruction manual

If an additional Model 7999-4 Instruction Manual is required, order the manual package,
Keithley part number 7999-4-901-00. The manual package includes an instruction manual and
any pertinent addenda.

Repacking for shipment

Should it become necessary to return the Model 7999-4 for repair, carefully pack the unit in
its original packing carton or the equivalent, and include the following information:

• Call the Repair Department at 1-800-552-1115 for a Return Material Authorization

• Advise as to the warranty status of the switch.

• Write ATTENTION REPAIR DEPARTMENT and the RMA number on the shipping

• Fill out and include the service form located at the back of this manual.

Connections

The following are available Model 7999-4 connections:

• Power receptacle: 3-pin phoenix jack for supplied power module

• RS-232 port: DB-9 connector

• Common, NC, and NO: 3-SMA (female) connectors

NOTE Refer to Section 2 for detailed connection information.

(RMA) number.

label.

2

Connections

2-2 Connections

Introduction

This section contains information about overall switch configuration and connections and is
organized as follows:

• Handling precautions

• Configuration

• Connections

WARNING The procedures in this section are intended only for qualified service per-

sonnel. Do not perform these procedures unless you are qualified to do so.
Failure to recognize and observe normal safety precautions could result in
personal injury or death.

Handling precautions

To maintain high-impedance isolation, care should be taken when handling the switch to
avoid contamination from such foreign materials as body oils. Such contamination can reduce
isolation resistance. To avoid possible contamination:

• Always grasp the switch by the case

• Do not touch connector insulators

• Operate the card in a clean environment. If the card becomes contaminated, it should be
thoroughly cleaned as explained in Section 4.

Configuration

Layout

Figure 2-1 shows the general layout of the Model 7999-4 which features:
Connectors:

• Power receptacle: 3-pin phoenix jack for supplied power module

• RS-232 port: DB-9 connector

• Common, NC, and NO: 3-SMA (female) connectors

Indicators:

• Power LED

• NC LED (normally closed relay)

• NO LED (normally open relay)

F

Connections 2-3

igure 2-1

SMA Connectors

General layout

NC LEDNO LED

NCCOMNO

CA-27-20D
Cable Assembly

J1003

Power Receptacle
(3-pin phoenix)

Power LED

RS-232 Port
(DB-9 connector)

F

2-4 Connections

Simplified schematic

arranged into four sections:

Figure 2-2 shows a simplified schematic diagram of the Model 7999-4. The schematic is

• Power

• RS-232 interface

• Relay control

• Relay

igure 2-2

Simplified
schematic

NO LED

SMA Connectors

NO

Relay

Relay
control

NC

C

COM

NO

NC LED

NC

3
0
0

J1

Power

J1010
3-Pin
jack

phoenix

RS-232
Interface

Power
LED

J1011
DB9

F

Connections

RS-232 Connection

Connections 2-5

The RS-232 serial port is connected to the serial port of a computer (controller) using a
straight-through RS-232 cable terminated with DB-9 connectors. Do not use a null modem
cable. The serial port uses the transmit (TXD), receive (RXD), and signal ground (GND) line
of the RS-232 standard. Figure 2-3 shows the Model 7999-4 connector with Table 2-1 contain­ing the pinouts for the connector.

If your computer uses a DB-25 connector for the RS-232 interface, an additional cable or
adapter (DB-25 to DB-9) is required.

igure 2-3

RS-232 interface
connector

NOTE In the RS-232 interface, only pins 2, 3, and 5 are used. Pins 7 and 8 are tied together,

but not connected to the circuit board. Pins 1, 4, and 6 are also tied tog ether and not
connected to the circuit board.

Table 2-1

RS-232 connector terminals

Pin Number Description

1 Tied to pins 4 and 6
2 TXD, Transmit data
3 RXD, Receive data
4 Tied to pins 1 and 6
5 GND, Signal ground
6 Tied to pins 1 and 4
7 Tied to pin 8
8 Tied to pin 7
9 Not used

RS232

5 4 3 2 1

9 8 7 6

2-6 Connections

SMA connectors

open), and NC (normally closed) connections of the relay.

Power connector

WARNING To prevent damage to the Model 7999-4, use only the Keithley Model

The Model 7999-4 has three SMA connectors which represents the Common, NO (normally

Connect the supplied power adapter (Model PS-57A) to the power connector.

PS-57A AC/DC power adapter. This is a universal input (100V - 240VAC,
50/60Hz), 12VDC output (3A or less) supply.

3

Operation

•

•

3-2 Operation

Introduction

This section contains operating information for the Model 7999-4. The information is orga-

nized as follows:

• Maximum signal considerations

• Toggle relay state switch

• Operation (RS-232)

• Switching considerations

Maximum signal considerations

WARNING Maximum voltage between any conductor and ground is 42V.

CAUTION T o prevent damage to the Model 7999-4, do not exceed the following maxi-

mum signal level specifications of the switch:

Maximum voltage: 30V DC, 42V peak
Maximum current: 1A DC, switched

T oggle relay state switch

Use this switch to manually toggle the relay, i.e., if the relay is closed, operating the switch
opens the relay, if the relay is open, operating the switch closes the relay. After operating this
spring loaded switch (pushing the switch left or right), the switch returns to the center (neutral)
position while the relay stays in the toggled position. Refer to Figure 3-1.

Figure 3-1

Toggle relay
state switch

NC

NO

TOGGLE RELAY STATE

Operation (RS-232)

Sending and receiving data

The Model 7999-4 relay is RS-232 controlled. Before the relay can be controlled, connect
an appropriate and properly configured controller to the DB-9 port. The Model 7999-4 serial
interface (RS-232) transfers data using 8 data bits, no parity, and 1 stop bit (8-N-1). The
interface also transfers data at 9600 baud. Make sure that the controller selected also uses these
settings.

T ermination characters

Operation 3-3

The Model 7999-4 can be configured to terminate each program message transmitted to the
controller with any of the following combinations of <CR> or <LF>:

<CR> Carriage return (factory default setting)

<CR+LF> Carriage return and line feed

<LF> Line feed

<LF+CR> Line feed and carriage return

To configure the termination character, change the jumpers for PA6 (J1006) and PA7
(J1008) located on the Model 7999-4 printed circuit board. Refer to Table 3-1 and Figure 3-2
for jumper details. Refer to the first three steps of disassembly information in Section 4 to
access the circuit board.

Table 3-1

Jumper positions—termination characters

Terminator J1006 pins J1008 pins

1

<CR>
<CR+LF> 2 and 3 1 and 2
<LF> 1 and 2 2 and 3
<LF+CR> 2 and 3 2 and 3

1

Factory default setting

1 and 2

1

1 and 2

1

Fi

2

3-4 Operation

gure 3-

Jumper location

1

1

RS-232 Commands

Refer to Table 3-2 for a list of commands included in the command set.

Table 3-2

Command set

Function ASCII Command Description

Open the relay O or o After the open command is sent, a 25msec delay

Close the relay C or c After the closed command is sent, a 25msec delay

Operation 3-5

occurs which allows the relay to settle. After the
relay settles, an ASCII ‘1’ is sent over the RS-232
indicating settling time has run out.

occurs which allows the relay to settle. After the
relay settles, an ASCII ‘1’ is sent over the RS-232
indicating settling time has run out.

Query relay state S or s Upon receiving this command, if the relay is closed

an ASCII 1 is returned; if the relay is open, an ASCII
0 is returned.

Firmware
information

NOTE ACSII characters not included in the command set are ignored.

I or i Firmware information can be retrieved over the

RS-232 using the ‘I’ command. After the command
is sent, ‘Keithley Instruments Inc., Model 7999-4,
rev A01’ (or similar due to firmware revision level)
will be returned over the RS-232.

Ω

3-6 Operation

Switching considerations

Signals switched by the Model 7999-4 may be subject to various effects that can seriously
affect their integrity. The following paragraphs discuss these effects and ways to minimize
them.

Connector integrity

As is the case with any high-resistance device, the inte grity of connectors can be damaged if
they are not handled properly. If connector insulation becomes contaminated, the insulation
resistance will be substantially reduced, affecting high-impedance measurement paths. Refer to
Section 4 for cleaning information.

Oils and salts from the skin can contaminate connector insulators, reducing their resistance.
Also, contaminants present in the air can be deposited on the insulator surface. To avoid these
problems, never touch the connector insulating material. In addition, use the relay only in
clean, dry environments to avoid contamination.

V oltage standing wave ratio

The Voltage Standing Wave Ratio (VSWR) is a measurement of mismatch in a cable,
waveguide, or antenna system. The measurement is shown as ratio to 1, e.g., a VSWR of 1.2 is
actually the ratio of 1.2:1. Refer to the specifications located at the front of this manual for
Model 7999-4 VSWR information (specifications are shown with a 50

Path isolation

The path isolation is the equivalent impedance between an y tw o test paths in a measurement
system. Ideally, the path isolation should be infinite, but the actual resistance and distributed
capacitance of cables and connectors results in less than infinite path isolation values for these
devices.

Path isolation resistance forms a signal path that is in parallel with the equivalent resistance
of the DUT. For low-to-medium device resistance values, path isolation resistance is seldom a
consideration; however, it can seriously degrade measurement accuracy when testing high­impedance devices. The voltage measured across such a device, for example, can be substan­tially attenuated by the voltage divider action of the device source resistance and path isolation
resistance. Also, leakage currents can be generated through these resistances by v oltage sources
in the system. Refer to the specifications located at the front of this manual for Model 7999-4
isolation information.

load).

Insertion loss

Insertion loss indicates signal lost while passing through the switch. This loss occurs in the
various signal path components through the switch connectors, PC board traces, and relay.
Refer to the specifications located at the front of this manual for Model 7999-4 insertion loss
information.

RFI/EMI

RFI (Radio Frequency Interference) and EMI (Electromagnetic Interference) are general
terms used to describe electromagnetic interference over a wide range of frequencies across the
spectrum. Such interference can be particularly troublesome at low signal le vels, b ut is can also
affect measurements at high levels if the problem is of sufficient severity.

Operation 3-7

EMI can be caused by steady-state sources such as radio or TV broadcast signals, or some
types of electronic equipment (microprocessors, high speed digital circuits, etc.), or it can
result from impulse sources, as in the case of arcing in high-voltage environments. In either
case, the effect on the desired signal can be considerable if enough of the unwanted signal is
present.

EMI can be minimized in several ways. The most obvious method is to keep the equipment
and signal leads as far away from the RFI source as possible. Shielding the switching switch,
signal leads, sources, and measuring instruments will often reduce RFI to an acceptable level.
In extreme cases, a specially constructed screen room may be required to suf ficiently attenuate
the troublesome signal.

4

Service Information

4-2 Service Information

Introduction

This section contains service information for the Model 7999-4. The information is orga-

nized as follows:

• Handling and cleaning precautions

• Performance verification

• Component replacement

WARNING The information in this section is intended only for qualified service per-

sonnel. Some of the procedures may expose you to hazardous voltages that
could result in personal injury or death. Do not perform these procedures
unless you are qualified to do so.

Handling and cleaning precautions

Because of the high-impedance areas on the Model 7999-4, care should be taken when han­dling or servicing the switch to prevent possible contamination. The following precautions
should be observed when servicing the switch.

Handling precautions

Observe the following precautions when handling the SPDT switch:

• Handle the switch only by the edges and cover.

• Do not touch connector insulators.

• Do not touch any board surfaces or components not associated with the repair.

• Do not touch areas adjacent to electrical contacts.

• When servicing the switch, wear clean cotton gloves.

• Do not store or operate the switch in an environment where dust could settle on the
circuit board.

Card and connector cleaning

• Use dry nitrogen gas to clean any dust off the circuit board and components.

• Clean the contaminated area with methanol, then blow dry the entire board with dry
nitrogen gas.

• If the connector insulators should become contaminated, either by inadvertent touching,
or from air-borne deposits, they can be cleaned with a cotton swab dipped in clean
methanol.

• Before use, allow items cleaned to dry for several hours in a 50˚C low-humidity
environment. Use dry nitrogen to decrease drying time.

Ω

Ω

Service Information 4-3

Performance verification

The following paragraphs discuss performance verification procedures for the Model 79 99-4

including a channel resistance verification procedure.

CAUTION Contamination will degrade the performance of the switch. To avoid

contamination, always grasp the switch by the cover; do not touch the
connectors.

NOTE Failure of any performance verification test may indicate that the microwave switch

is contaminated. See “Handling and cleaning precautions” earlier in this section for
information on cleaning the switch.

Environmental conditions

All verification measurements should be made at an ambient temperature between 18˚ and

28˚C, and at a relative humidity of less than 70%.

Recommended equipment

Table 4-1 summarizes the equipment necessary for performance verification (channel resis-

tance tests).

Table 4-1

Recommended verification equipment

Manufacturer/Model Equipment Description Specifications

Keithley 2010 Digital Multimeter 10 Ω range, 60ppm
Keithley 1681 Test Lead Sets (2) Banana plug/clips

Channel resistance tests

Perform the following steps to verify that the relays contact is closing properly, the relay

resistance is within specification, and that the relay opens properly.

1. Turn on the Model 2010 DMM, and allow it to warm up for one hour before making
measurements.

2. Set the Model 2010 to the 10
SENSE

3. Short the free ends of the four test leads together, and enable REL on the Model 2010 to
null out residual resistance. Leave REL enabled for the entire test.

4 WIRE jacks.

range, and connect the four test leads to the INPUT and

Fi

1

Ω

4-4 Service Information

4. Connect the Model 2010 INPUT and SENSE Ω 4 WIRE jacks to the NC relay contact
and common, as shown in Figure 4-1.

NOTE Use 4-wire connections.

5. Close the relay.

6. Note the resistance reading on the Model 2010, and verify that it is <0.1

7. Open the relay.

8. Note the resistance reading on the Model 2010, and verify that it indicates an open cir­cuit.

9. Repeat the measurement for the NO relay (repeat steps 4 through 8 but with the DMM
connected to the NO relay contact and common).

.

gure 4-

Channel resistance
test connections

Connect to INPUT and SENSE

STEP CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10
TALK
LSTN
SRQ
SHIFT
TIMER

HOLD TRIG FAST MED SLOW AUTO ERR

MX+B

SHIFT

DCV

HOLD

LOCAL

TRIG

EX TRIG

POWER

SAVE SETUP

OPEN CLOSE

SCAN

ACV

%

CH1REM

dBm

DCI

STORE

CONFIG HALT

REL FILT4WBUFFER

dB

ACI

LIMITS ON/OFFDELAY

RECALL

STEP SCAN

MATH
REAR

STAT

CONT PERIOD SENSOR

FREQ

ý2 ý4

TYPE

DRYCKT O COMP

RATIO

RELFILTER

RS232

CAL TEST

GPIB

EXIT ENTER

DIGITS RATE

2010 MULTIMETER

TEMP

ý 4 WIRE

HI

350V

1000V

!

PEAK

PEAK

LO

500V
PEAK

INPUTS

F

R

RANGE
AUTO

FRONT/REAR

3A 250V

RANGE

AMPS

Common

>>

>>

Closed
Relay

SENSE

INPUT

Relay
(NC or NO)

Model 2010 DMM

Model 7999-4 Relay
Under Test. See Section 2
for Detailed Connections.

•

•

Replacing components

Replacement parts

Replacement parts can be obtained directly from Keithley Instruments, Inc. See the parts list

in Section 5 for part numbers.

Replacement precautions

CAUTION Observe the following precautions when replacing components:

Service Information 4-5

To avoid contamination, which could degrade switch performance,
always handle the switch only by the covers and side edges. Do not
touch the connector, board surfaces, or components on the switch.

Use care when removing components from the PC board to avoid pull­ing traces away from the circuit board. Before attempting to remove a
relay, use an appropriate de-soldering tool, to clear each mounting
hole completely free of solder.

Soldering considerations

When using solder on the circuit board, observe the following precautions:

• Use an OA-based (organic activated) flux, and take care not to spread the flux to other
areas of the circuit board.

• Remove the flux from the work areas when the repair has been completed. Use pure
water along with clean cotton swabs or a clean soft brush to remove the flux.

• Once the flux has been removed, swab only the repaired area with methanol, then blow
dry the board with dry nitrogen gas.

• After cleaning, allow the card to dry in a 50˚C low-humidity environment for several
hours before use.

Disassembly

Perform the following steps to disassemble the Model 7999-4 to gain access to parts on the

circuit board:

1. Remove the six screws that hold the case together and the two hex-nuts on the DB9
connector.

2. Separate the two halves of the case.

3. Unplug the connector from the relay.

4. Remove the screws that secure the PC board to the case, then remove the board.

5

Replaceable Parts

5-2 Replaceable Parts

Introduction

This section contains replacement parts information and component layout for the

Model 7999-4.

Parts list

Parts lists for the Model 7999-4 are contained in Table 5-1 and Table 5-2.

Ordering information

To place an order, or to obtain information concerning replacement parts, contact your
Keithley representative or the factory (see inside front cover for addresses). When ordering
parts, be sure to include the following information:

• Switch model number (Model 7999-4)

• Serial number

• Part description

• Component designation (if applicable)

• Keithley part number

Factory service

If the switch is to be returned to Keithley Instruments for repair, perform the following:

• Call the Repair Department at 1-800-552-1115 for a Return Material Authorization
(RMA) number.

• Complete the service form at the back of this manual, and include it with the
instrument.

• Carefully pack the instrument in the original packing carton.

• Write ATTENTION REPAIR DEPARTMENT and the RMA number on the shipping
label.

Replaceable Parts 5-3

Component layout

The following component layout drawing is provided on the following page:

• Component layout drawing: 7999-4-100

Table 5-1

Parts list—electronic components

Circuit designation Description Keithley part no.

C105, C114 CAP, 33PF, 10%, 100V, CERAMIC C-451-33P
C106 CAP, 0.1UF, 20%, 50V, CERAMIC C-418-.1
C107, C108,
C115–C119
C110, C112, C113 CAP, 10UF, 20%, 25V, TANTALUM C-440-10
CR101–CR103 DIODE, DUAL SWITCHING RF-82
DS101 PILOT LIGHT, GREEN, LED PL-78
J1001, J1005 LATCHING HEADER, FRICTON, SGL ROW CS-724-3
J1003 (cable) CABLE ASSEMBLY CA-27-20D
J1006–J1009 CONN, BERG CS-339
J1010 CONN, HORIZ, RECEPTACLE 3-PIN CS-943-3
J1011 CONN, RT ANGLE, MALE, 9-PIN CS-761-9
Q101 TRANS, NPN SILICON TG-389
R103, R107–R110,
R115–R118
R104 RES, 4.02K, 1%, 100mW THICKFILM R-418-4.02K
R111, R112, R114 RES, 4.75K, 1%, 100mW THICKFILM R-418-4.75K
R113 RES, 10M, 5%, 125mW METAL FILM R-375-10M
R V110 TRANSIENT VOL TAGE SUPRESSOR VR-12
R V120 TRANSIENT VOL TAGE SUPRESSOR VR-11
U107 IC, UNDERVOLTAGE SENSE CIRCUIT IC-1067
U108 IC, RS-232 LINE DRIVER/RECEIVER IC-1129
U105 IC, 8-BIT MICRO PROCESSOR 7999-4-800A01
U106 IC, +5V REGULATOR, 500mA IC-93
VR101 DIODE, ZENER, 6.2V DZ-97
Y101 CRYSTAL, 4MHZ CR-36-4M

CAP, 0.1UF, 10%, 25V, CERAMIC C-495-.1

RES, 10K, 1%, 100mW THICKFILM R-418-10K

5-4 Replaceable Parts

Table 5-2

Parts list—mechanical parts

Description Keithley part no.

Bracket (relay) 7999-4-304A
Cover (bottom) 7999-4-302A
Cover (top) 7999-4-301A
Female screw-lock CS-725
Lock-nut 4-40KEPNUT
Phillips Pan Head Screw 4-40X1/4PPH
Phillips Pan Head Screw SEMS (black) 4-40X3/8PPHSEMBLK
Phillips Pan Head Screw SEMS (relay attaching hardw are) 2-56x5/8PPHSEM

Index

C

Card cleaning
Carriage return
Carriage return and line feed
Channel resistance tests
Component layout
Configuration
configure termination character
connections

4-2

2-2

1-4
introduction
RS-232

2-5

SMA

2-6

3-3

D

Disassembly

4-5

E

Environmental conditions

F

Factory service
Feature overview
flux

4-5

5-2

G

general information

H

Handling
Handling precautions

4-2

I

Insertion loss
Inspection for damage
Instruction manual

3-7

2-2

1-2

5-3

1-4

1-2

M

Manual addenda
Maximum signal considerations

1-2

3-2

O

4-3

3-3

3-3

Opening or closing the relay
Operation

Introduction

RS-232
Ordering information
overview

3-2

3-3

1-2

3-5

5-2

P

Parts list
Path isolation
Performance verification

5-2

3-6

4-3

R

3-7

1-4

5-2

4-5

4-5

4-5

2-5

Repacking

4-3

Repair Department Phone Number
Replacement parts
Replacement precautions
Replacing components
RFI/EMI
RS-232 connector terminals

S

Safety symbols and terms
schematic
Sending and receiving data
Shipment contents
signal considerations

1-3

2-2

1-3

4-2

,

,

Soldering considerations
Switching considerations
symbols and terms

T

Termination characters

2-4

1-3

3-3

1-4

3-2

4-5

3-6

1-3

3-3

J

J1006

3-3

J1008

3-3

Jumper location

L

Layout

2-2
Line feed
Line feed and carriage return

3-3

U

Unpacking and inspection

3-4

V

Voltage Standing Wave Ratio

1-3

3-6

W

Warranty

1-2

3-3

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

❑

Service Form

Model No. _______________ Serial No. __________________ Date _________________
Name and Telephone No. ____________________________________________________
Company _______________________________________________________________________

List all control settings, describe problem and check boxes that apply to problem. _________________________

__________________________________________________________________________________________
__________________________________________________________________________________________

Intermittent

IEEE failure
Front panel operational ❑ All ranges or functions are bad

Analog output follows display

Obvious problem on power-up

Particular range or function bad; specify

_______________________________

Batteries and fuses are OK
Checked all cables

Display or output (check one)

Drifts
Overload

Calibration only

(attach any additional sheets as necessary)
Show a block diagram of your measurement including all instruments connected (whether power is turned on or

not). Also, describe signal source.

Where is the measurement being performed? (factory, controlled laboratory, out-of-doors, etc.)_______________

__________________________________________________________________________________________

What power line voltage is used?___________________ Ambient temperature? ________________________°F
Relative humidity? ___________________________________________Other? __________________________
Any additional information. (If special modifications have been made by the user, please describe.)

__________________________________________________________________________________________
__________________________________________________________________________________________

Be sure to include your name and phone number on this service form.

Unable to zero
Will not read applied input

Certificate of calibration required

Unstable

Data required

Keithley Instruments, Inc.

28775 Aurora Road
Cleveland, Ohio 44139

Printed in the U.S.A.