AR 200T26z5G40A Series Service manual

Operating and
Service Manual
200T26z5G40A
Model
10027190
Part Number
Serial Number
160 School House Road, Souderton, PA 18964 • 215-723-8181 • Fax [phone] • www.arworld.us

EC Declaration of Conformity
We: Amplifier Research
160 School House Road
Souderton, PA. 18964
declare that our product(s);
the Model 200T26z5G40A series RF amplifiers
to which this declaration relates is in compliance with the following European directives:
Low Voltage Directive: 2014/35/EU
EMC Directive: 2014/30/EU
Supplementary Information:
Safety : EN 60215-1:1989
EN 61010-1:2010
EMC: EN 61000-6-2:2005, EN61000-6-4:2007
Year Mark Applied: 2016
I, the undersigned, hereby declare that the equipment specified above conforms to the above Directives and
Standards.
Authorized officer of the company:
James M. Maginn
President

INSTRUCTIONS FOR SAFE OPERATION
Revised 0517
Observe the following safety guidelines to help ensure your
own personal safety and to help protect your equipment and
working environment from potential damage.
INTENDED USE
This equipment is intended for general laboratory use in
generating, controlling, and measuring levels of
electromagnetic Radio Frequency (RF) energy. Ensure that the
device is operated in a location which will control the radiated
energy and will not cause injury or violate regulatory levels of
electromagnetic interference.
SAFETY SYMBOLS
These symbols may appear in your user manual or on
equipment.
This symbol is marked on the equipment when it
is necessary for the user to refer to the manual for
important safety information.
The caution symbol denotes a potential hazard.
Attention must be given to the statement to
prevent damage, destruction, or harm.
Dangerous voltages are present. Use extreme
care.
Indicates a terminal intended for connection to an
external conductor for protection against
electrical shock in case of a fault, or the terminal
of a protective earth (ground) electrode.
Indicates invisible laser radiation–do not view
directly with optical instruments.
Indicates frame or chassis ground connection
terminal.
Indicates alternating current.
Indicates this product must not be disposed of
with your other household waste.
Indicates that the marked surface and adjacent
surfaces can attain temperatures that may be hot
to the touch.
EQUIPMENT SETUP PRECAUTIONS
Review the user manual and become familiar with
all safety markings and instructions. Protection
provided by the equipment may be impaired if used
in a manner not specified by AR RF/Microwave
Instrumentation (AR).
•Follow all lifting instructions specified in this document.
•Place the equipment on a hard, level surface.
•Do not use the equipment in a wet environment, for
example, near a sink, or in a wet basement.
•Position your equipment so that the power switch is easily
accessible.
•Leave 10.2 cm (4 in) minimum of clearance on all vented
sides of the equipment to permit the airflow required for
proper ventilation. Do not restrict airflow into the
equipment by blocking any vents or air intakes. Restricting
airflow can result in damage to the equipment, intermittent
shut-downs or safety hazards.
•Keep equipment away from extremely hot or cold
temperatures to ensure that it is used within the specified
operating range.
•While installing accessories such as antennas, directional
couplers and field probes, take care to avoid any exposure
to hazardous RF levels.
•Ensure that nothing rests on your equipment’s cables and
that the cables are not located where they can be stepped
on or tripped over.
•Move equipment with care; ensure that all casters and/or
cables are firmly connected to the system. Avoid sudden
stops and uneven surfaces.
BEFORE APPLYING POWER
Your AR equipment may have more than one power supply
cable. Use only approved power cable(s). If you have not been
provided with a power cable for the equipment or for any AC-
powered option intended for the equipment, purchase a power
cable that is approved for use in your country. The power cable
must be rated for the equipment and for the voltage and current
marked on the equipment’s electrical ratings label.
Incorrectly installing or using an incompatible line
voltage may increase the risk of fire or other
hazards. To help prevent electric shock, plug the
equipment and peripheral power cables into properly grounded
electrical outlets. These cables are equipped with three-prong
plugsto help ensure proper grounding. Do not useadapterplugs
or remove the grounding prong from a cable.
Do not modify power cables or plugs. Consult a licensed
electrician or AR trained service technician for equipment
modifications. Always follow your local/national wiring rules.
Do not operate the equipment if there is physical
damage, missing hardware, or missing panels.
SAFETY GROUND
This equipment is provided with a protective earth
terminal. The mains power source to the equipment
must supply an uninterrupted safety ground of
sufficient size to attach wiring terminals, power
cord, or supplied power cord set. DO NOT USE this equipment
if this protection is impaired.

INSTRUCTIONS FOR SAFE OPERATION
Revised 0517
HAZARDOUS RF VOLTAGES
The RF voltages on the center pin of an RF output
connector can be hazardous. The RF output
connector should be connected to a load before AC
power is applied to the equipment. Do not come into
contact with the center pin of the RF output connector or
accessories connected to it. Place the equipment in a non-
operating condition before disconnecting or connecting the load
to the RF output connector.
ACOUSTIC LIMITATIONS
If equipment noise exceeds 80dB, ear protection is required.
MAINTENANCE CAUTION
Adjustment, maintenance, or repair of the equipment must be
performed only by qualified personnel. Hazardous energy may
be present while protective covers are removed from the
equipment even if disconnected from the power source. Contact
may result in personal injury. Replacement fuses are required
to be of specific type and current rating.
ENVIRONMENTAL CONDITIONS
Unless otherwise stated on the product specification sheet, this
equipment is designed to be safe under the following
environmental conditions:
•Indoor use
•Altitude up to 2000m
•Temperature of 5°C to 40°C
•Maximum relative humidity 80% for temperatures up to
31°C. Decreasing linearly to 50% at 40°C.
•Main supply voltage fluctuations not to exceed ± 10% of
the nominal voltage or minimum and maximum
autoranging values.
•Pollution degree 2: Normally non-conductive with
occasional condensation. While the equipment will not
cause hazardous condition over this environmental range,
its performance may vary.
EQUIPMENT CONTAINING LASERS
AR Field Probes (FL/PL Series) and Field Analyzers
(FA Series) are Class 1 laser products containing
embedded Class 4 lasers. Under normal use, the
laser radiation is completely contained within the
fiber optic cables and poses no threat of exposure. Safety
interlocks ensure that the laser is not activated unless the cables
are properly connected. Always exercise caution when using
or maintaining laser products. Do not view directly with optical
instruments.
RF ANTENNAS
•This equipment (antenna or antenna assembly) may be
heavy, requiring two persons to lift. Use caution when
installing or removing unit. Follow all equipment setup and
lifting instructions specified in this document.
•Ensure connectors are appropriate for intended operation.
Connectors are specified in the user manual and product
specification sheet.
•Do not exceed the maximum RF input level stated in the
specifications. Refer to the user manual and product
specification sheet to determine the applicable RF levels.
•Excessive RF input could damage the equipment or
connectors, causing safety hazards.
•When in operation, the RF voltages on the antenna
elements can be hazardous. Do not come into contact with
the antenna or elements when the RF input connector is
connected to a live RF source.
•To avoid injury to personnel and accidental damage to
power amplifier or antenna, disable the RF output of power
amplifier before connecting or disconnecting the input
connection to the antenna.
•Perform periodic inspections of antenna and field probe
systems to verify calibration due date, proper operation,
and overall condition of equipment.
RACK MOUNTED TWT MODELS
Some TWT models are supplied without the removable
enclosure offered for benchtop use. These rack-mountable
models may be supplied with either carry handles or slides and
front handles installed. Follow all lifting instructions specified
in this document and installation instructions supplied in the
TWT user manual.
LIFTING INSTRUCTIONS FOR AR EQUIPMENT
Because most products must be
handled during distribution, assembly
and use, the risk of serious injury due
to unsafe product handling should be
a fundamental consideration of every
user. An authoritative guideline for
eliminating unwarranted risk of injury caused by lifting is
provided by the NIOSH Work Practices (Publication #94-110)
available at:
https://www.cdc.gov/niosh/docs/94-110/pdfs/94-110.pdf.
In general, observe the following guidelines for lifting a weight
of 50 lb or more:
•Use lifting eye (for floor standing) or side handles (table
top) to lift unit only.
•Use equipment of adequate capacity to lift and support unit.
•If using forklift to move unit, be sure forks are long enough
to extend beyond the side of the unit.
•For additional information, follow the link specified above.

ADDITIONAL WARNINGS & NOTES
WARNING:
This equipment operates at potentially lethal voltages. Only trained,
qualified personnel should operate, maintain, or service it.
Hazardous energy may be present while protective covers are removed
from the equipment even if disconnected from the power source. Contact
may result in personal injury.
CAUTION:
Adjustment, maintenance, or repair of the equipment must be performed
only by qualified personnel.
CAUTION:
Replacement fuses are required to be of specific type and current rating.
CAUTION:
The information in this document was obtained from reliable sources and
was believed to be accurate at the time of publication. Since subsequent
modifications to the machine may have been made, use this information
only as a guide. Carefully compare the unit's actual configuration and
operation to the descriptions in this manual before you undertake to
operate, service, or modify this machine. Any variance or modification
should be noted, dated, and initialed in the discrepant part of all manuals
on hand for future reference. If you have technical or editorial comments
you wish to make to the manufacturer, please write them on photocopies
of the relevant sheets.
NOTE: The contents of this document are the property of the manufacturer and this document is delivered
on the express condition that it not be disclosed, reproduced in whole or in part, or used for manufacture for
anyone other than the manufacturer without its written consent, and that no right is granted to disclose or
so use any information in this document.

TABLE OF CONTENTS
TABLE OF CONTENTS.................................................................................................. i
1. DESCRIPTION AND SPECIFICATIONS........................................................1
1.1 TWTA Description.................................................................................................1
1.2 Suggested Applications..........................................................................................1
1.3 Specifications.........................................................................................................1
1.4 Accessories.............................................................................................................1
1.5 Test Data Sheet ......................................................................................................2
2. THEORY OF OPERATION...............................................................................5
2.1 Design of the amplifier...........................................................................................5
2.2 Description of the RF aSSEMBLY........................................................................5
2.3 Description of the Power Supply ...........................................................................6
3. OPERATION........................................................................................................7
3.1 Warnings and Cautions ..........................................................................................7
3.2 Installation..............................................................................................................7
3.2.1 Unpacking ..............................................................................................................7
3.2.2 Mounting................................................................................................................8
3.2.3 Cooling Requirements............................................................................................9
3.2.4 AC Line Power Connections..................................................................................9
3.2.5 RF Output Connections..........................................................................................9
3.2.6 External Interlock Connector ...............................................................................10
3.2.7 External IEEE-488 Connector..............................................................................10
3.3 Front Panel Features.............................................................................................11
3.4 Front Panel Display and Soft Keys......................................................................12
3.5 Rear Panel Features..............................................................................................16
3.6 Initial Turn On and Warm-up Procedure .............................................................17
3.7 Foldback Operation..............................................................................................18
3.8 Remote IEEE-488 Operation................................................................................18
3.9 TWTA General Considerations............................................................................23
4. MAINTENANCE ...............................................................................................27
4.1 Safety Warning.....................................................................................................27
4.2 Unauthorized Repairs...........................................................................................27
4.3 Preventive Maintenance.......................................................................................27
4.4 Troubleshooting ...................................................................................................28
4.5 Non-Repairable Modules .....................................................................................29
5. TECHNICAL DOCUMENTATION................................................................31
5.1 Top Level Build Tree...........................................................................................32
5.1.1 A33961-000, 200 Watt K Band HPA...................................................................32
5.1.2 A33962-000, 200 Watt KA Band HPA................................................................33
5.2 Schematics............................................................................................................34
5.3 Parts Lists.............................................................................................................35
5.3.1 Parts List, 200T 18G26z5A & 26z5G40A, HPA Logic and Control Module for
130K, 130KA, A16485-893.................................................................................36

Models 200T18G26z5A/200T26z5G40A
5.3.2 Parts List, 200T18G26z5A, HV Power Supply For L-3 TWT 8928H (Pulsed 2-Tube
Unit), A22826-930 ...............................................................................................38
5.3.3 Parts List, 200T26z5G40A, HV Power Supply For L-3 TWT 8929H, A22826-931
..............................................................................................................................38
5.3.3 Emergency Bypass Board, Low Level Foldback Trip (<1V); A24830-011........39
5.3.4 Parts List, HPA Interface Board (200UM Glass Fibers), A25444-001 ...............40
5.3.5 Parts List, 200T18G26z5A, Microwave Power Assembly 200 Watt K-Band; A
28051-341.............................................................................................................43
5.3.6 Parts List, 200T26z5G40A, Microwave Power Assembly 200KA, A28051-35144
5.3.7 Parts List, Wiring Kit, 200W KA Band (Glass Fibers); A28052-002.................45
5.3.8 Parts List, VSWR/Foldback Board Assembly, A32363-000...............................47
5.3.9 Parts List, HPA 200 Watt K-Band W/ 2 L3 Tubes (AR), A33961-000...............49
5.3.10 Parts List, HPA 200 Watt KA-Band W/ 2 L3 Tubes (AR), A33962-000............49
5.4 Sample Program...................................................................................................50
Figures
3-1 Rack Mounting Configuration ...............................................................................8
3-2 TWTA Front Panel Features................................................................................11
3-3 Front Panel Display Screens ................................................................................12
3-4 TWTA Rear Panel Features.................................................................................16
Tables
3-1 Front Panel Features.............................................................................................11
3-2 Rear Panel Features..............................................................................................16
3-3 Catalog of IEEE-488 Commands .........................................................................18
3-4 Catalog of Status Codes .......................................................................................20
3-5 Catalog of Fault Codes.........................................................................................20
3-6 Catalog of System State Codes ............................................................................21
3-7 Catalog of *STA?; Response Codes ....................................................................21
3-8 Catalog of *STB?; Response Codes.....................................................................22
3-9 Catalog of Heater Auto Off Time Delay Codes...................................................22

Rev – 1
1. DESCRIPTION AND SPECIFICATIONS
This manual provides operating, interfacing and selected service information pertinent to AR Model
200T18G26z5A and 200T26z5G40A Broadband Microwave Amplifiers. These Models are 200 watt
broadband K- and Ka- band traveling-wave tube amplifiers (TWTA) respectively. This manual
supports models offering additional special features. Refer to the model specification sheet to
determine the applicable features of these units.
1.1 TWTA DESCRIPTION
The amplifier uses two power-combined broadband traveling-wave tubes (TWTs) to provide 200 watts
minimum output over the TWT amplifier's full bandwidth. The amplifier is well suited for susceptibility and
general laboratory testing where instantaneous bandwidth and high gain are required.
The amplifier is completely self-contained and packaged for standard 19-inch rack mounting or bench top
use. The front panel of the rack mountable amplifier is 15.7 inches (9U) high, and the overall unit is 28.4
inches deep, including the rear-panel connectors and vent housing. For bench top use, the amplifier is
supplied in an enclosure with integral carrying handles.
Primary power is 190-260 volts 50-60 Hz., single phase. An efficient switching power supply design
provides minimum power consumption. A fast regulation control loop and a high degree of filtering ensure
performance within specifications over a wide range of operating conditions. The amplifier is fully enclosed,
and the upper and lower panels of the rack mountable amplifier are interlocked to reduce the likelihood of
accidental contact with high voltage.
1.2 SUGGESTED APPLICATIONS
•RF Susceptibility testing
•Antenna and component testing
•Equipment calibration
•General laboratory instrumentation
1.3 SPECIFICATIONS
Refer to the AR Data Sheet at the end of this section for detailed specifications.
1.4 ACCESSORIES
AR offers a number of accessories for use with this amplifier including:
•Directional coupler
•Antenna
•Flexible transmission line
Refer to a current AR catalog for Microwave Accessories.

Models 200T18G26z5A/200T26z5G40A
2 Rev –
1.5 TEST DATA SHEET
A Test Data Sheet for a specific unit is prepared at the time of manufacture and is included with the unit's
copy of this manual.

The rated power is developed by efficiently
power combining the outputs from two 120
watts (nominal) microwave tubes that are fac-
tory matched in gain and phase.
Housed in a stylish contemporary cabinet, the
unit is designed for benchtop use but can be
removed from the cabinet for rack mounting.
The Model 200T26z5G40A provides readily
available RF power for a variety of applications
in Test and Measurement, (including EMC RF
susceptibility testing), Industrial and University
Research and Development, and Service appli-
cations. This sub-octave amplifier features
moderate harmonic content.
The export classification for this equipment is
EAR99. These commodities, technology or
software are controlled for export in accord-
ance with the U.S. Export Administration Regu-
lations. Diversion contrary to U.S. law is pro-
hibited.
See Model Configurations for alternative pack-
aging.
The Model 200T26z5G40A is a self contained,
forced air cooled, broadband traveling wave
tube (TWT) microwave amplifier designed for
applications where wide instantaneous band-
width, high gain and moderate power output
are required. A reliable TWT subsystem pro-
vides a conservative 200 watts minimum at the
amplifier output connector. Stated power spec-
ifications are at the fundamental frequency.
The amplifier's front panel digital display
shows forward and reflected output plus exten-
sive system status information accessed
through a series of menus via soft keys. Status
indicators include power on, warm-up,
standby, operate, faults, excess reflected power
warning and remote. Standard features in-
clude a built-in IEEE-488 (GPIB) interface,
0dBm input, VSWR protection, gain control,
forward and reflected RF output sample ports,
auto sleep, plus monitoring of TWT helix cur-
rent, cathode voltage, collector voltage, heater
current, heater voltage, baseplate temperature
and cabinet temperature. Modular design of
the power supply and RF components allow for
easy access and repair. Use of a switching
mode power supply results in significant weight
reduction.
Features
Specifications
200T26z5G40A
 M1 through M5
 200 Watts CW
 26z5GHz–40GHz
AR RF/Microwave
Instrumentation
160 School House Rd
Souderton, PA 18964
215-723-8181
For an applications engi-
neer call:800.933.8181
www.arworld.us
Model 200T26z5G40 Typical Power Output

POWER (fundamental), CW
@ OUTPUT CONNECTOR:
Nominal 225 watts
Minimum 200 watts
Linear @ 1dB Compression 50 watts minimum
FLATNESS: ±10 dB maximum
FREQUENCY RESPONSE: 26z5–40 GHz instantane-
ously
INPUT FOR RATED OUTPUT: 1.0 milliwatt maximum
GAIN (at maximum setting): 53 dB minimum
GAIN ADJUSTMENT (continuous range): 35 dB mini-
mum
INPUT IMPEDANCE: 50 ohms, VSWR 2.0:1 maximum
OUTPUT IMPEDANCE: 50 ohms, VSWR 2.5:1 typical
MISMATCH TOLERANCE: Output power foldback pro-
tection at reflected power exceeding 40 watts. Will op-
erate without damage or oscillation with any magni-
tude and phase of source and load impedance. May
oscillate with unshielded open due to coupling to in-
put. Should not be tested with connector off.
MODULATION CAPABILITY: Will faithfully reproduce
AM, FM, or pulse modulation appearing on the input
signal. AM peak envelope power limited to specified
power.
VIDEO PULSE CAPABILITY:
Pulse Width 0.1 microseconds min
Pulse Rate (PRF) 10kHz max
Duty Cycle: Some restrictions apply. Con-
tact AR with application re-
quirements.
RF Rise and Fall 100 ns max (10% to 90%)
Delay 500 ns max from pulse input to
RF 90%
Pulse width distortion 200 ns max (50% points of out-
put pulse width compared to
50% points of input pulse
width)
Noise Power Density (pulse off)
Minus 140 dBm/Hz (typical)
Pulse Off Isolation 80 dB minimum, 90 dB typical
Pulse Input: TTL Level, 50 Ohm nominal
termination, high level enables
RF when video pulsing mode is
selected.
NOISE POWER DENSITY:
Minus 70 dBm/Hz (maximum)
Minus 75 dBm/Hz (typical)
HARMONIC DISTORTION:
Minus 20 dBc maximum
Minus 30 dBc typical
PRIMARY POWER: 190-265 VAC, 50/60 Hz, single
phase, 3 kVA maximum
CONNECTORS:
RF input
RF output
Type K female on rear panel
Type WR–28 waveguide
flange on rear panel
RF output sample ports Type K female on rear panel
GPIB IEEE-488 on rear panel
Interlock DB-15 (f) on rear panel
Video BNC female on rear panel
COOLING: Forced air (self contained fans), air entry
and exit in rear.
WEIGHT: 91 kg (200 lbs)
SIZE: 50.3 x 43 x 81 cm (19.8 x 17 x 32 in)
EXPORT CLASSIFICATION: EAR99
Page 2
Specifications
200T26z5G40A
 M1 through M5
 200 Watts CW
 26z5GHz–40GHz
EPackage Alternatives. May select an alternative
from the following [E1C or (E1C and E2S)
and/or E3H]:
E1C Cabinet: Without outer enclosure, size 49 x
40 (9U) x 76 cm, 19 x 15.75 (9U) x 30 in.,
Subtract approximately 14 kg, 30 lbs, for
removal of outer enclosure.
E2S Slides: slides installed, add approximately 5
lbs, 2 kg.
E3H Handles: Front handles installed.
Model Configurations
Model number example: Model 200T26z5G40AM2
would have option E3H front handles installed.
To order AR Products, call 215.723.8181. For an applications engineer call:800.933.8181. Direct to Service call: 215.723.0275 or
email: [email protected] For Faxing Orders:866.859.0582 (Orders Only Please) [e-mail]
Approved for public release by AR RF/Microwave Instrumentation 032315
Model Number Features
200T26z5G40A Base model
M1 E1C
M2 E3H
M3 E1C & E3H
M4 E1C & E2S
M5 E1C & E2S & E3H

Rev – 5
2. THEORY OF OPERATION
2.1 DESIGN OF THE AMPLIFIER
The TWT amplifier consists of four principal subsystems. Two of these subsystems, the microwave power
assembly and the TWT power supplies are discussed in sections 2.2 and 2.3, respectively.
The other two subsystems are the microprocessor control system and the TWTA packaging. These both
consist of a number of subassemblies. See the build tree in section 5.1 for further information about how the
parts lists are structured.
The heart of the microprocessor control system is the control head assembly, which consists of the CPU
board, the HPA display board, and the data link board. The microprocessor control system supervises the
power supply, provides metering display, processes operator front panel inputs, and enables communication
with a host computer over the IEEE-488 interface.
The control head is provided with its own power supply and, other than thru the IEEE-488 interface bus, is
electrically isolated from the amplifier. Communication with the amplifier is via fiber optic links to the HPA
interface assembly.
The TWTA packaging consists of two cabinet assemblies secured as one. The cooling system utilizes two 60
Hz fans to cool the HV power supplies and a pair of hi speed 400Hz fans to cool the TWTs.
2.2 DESCRIPTION OF THE RF ASSEMBLY
The TWTA consists of two stages of RF amplification. The first stage is a solid-state preamp assembly with
adjustable gain followed by the last stage using a pair of power combined traveling-wave tubes.
The Type K RF input connector is located on the rear panel, or optionally on the front panel depending on
configuration. The RF input is fed through an input isolator to the input connector on the solid-state preamp.
The solid-state preamp's output drives into a magic tee/splitter assembly that incorporates phase shifters to
permit adjustment for optimized phase matching. The two outputs drive the RF input of each TWT. The RF
output of each TWT is through a waveguide flange. Each output passes through a reverse directional coupler
used to monitor for high reflected power due to excessive load VSWR and/or internal RF component failure.
High reflected power will cause a fault and take the unit out of Operate mode.
The output power of both two couplers is combined at a magic tee assembly before being directed through a
dual directional coupler. The output coupler provides forward and reverse samples for both monitoring and
protection. The reflected port on this directional coupler is routed to a detector diode. The detector output is
used for reverse power measurement on the HPA interface board. A sample of the reverse power is optionally
located on the front or rear panels.
The forward port of the directional coupler is split with a 10 dB coupler. One output is connected to a
detector diode. The output of the detector diode is used on the HPA interface board to measure forward
power. The other output is connected to the RF sample port on the rear panel or, optionally, on the front
panel depending on configuration. The coupler waveguide terminates in a WR-42 waveguide flange in the
18G26 and WR-28 waveguide flange in the 26G40 that protrudes through the rear panel of the TWTA.

Models 200T18G26z5A/200T26z5G40A
Amplifier gain is determined by a single solid-state preamp (SSPA), which has a voltage-controlled
attenuator. The control head determines the output of a digital-to-analog converter (DAC) on the HPA
interface board. The output of the DAC controls the SSPA attenuator.
2.3 DESCRIPTION OF THE POWER SUPPLY
The two TWT power supplies are of modular construction. The low voltage power supply modules provide
low voltage power for logic and control of all power supply assemblies. In addition these modules provide
DC power for the HPA interface. Control logic and TWT protection circuits are contained in the HPA Logic
and Control Assemblies.
Each high voltage power supply consists of the following: the Power Factor Correction module converts line
voltage to DC for the high voltage switching supply. Switching transistors, controlled by the Pulse Width
Modulation (PWM) Board, are on the Power Board Assembly. The high voltage transformer and rectifiers
are contained in the High Voltage Diode/Cap Assembly. The high voltage DC is filtered in the HV Filter
Assemblies. The same Focus Electrode Modulator is used on both the 18G26 and the 26G40 models.
Low voltage interconnects between the power supply modules are through a motherboard. It is installed in a
finned heat sink assembly to which the modules are bolted. Incoming cabinet air-cools the heat sink.

Rev – 7
3. OPERATION
3.1 WARNINGS AND CAUTIONS
Throughout this manual, the symbol:
WARNING:
Indicates that a hazard exists that may result in personal injury or loss of life.
CAUTION:
Indicates that failure to follow procedures may result in damage to the
equipment.
WARNING: DANGER - High Voltage Present:
Electrical equipment in this TWTA generates and stores high-voltage
energy that can result in fatal electrocution. Do not operate the TWTA
with covers or the front panel removed.
Only technicians thoroughly familiar with the high-voltages present in
microwave tube amplifiers must perform Service work in general, and
with this equipment in particular.
Never handle the TWT leads or the high-voltage connectors unless the
unit has been unplugged and it has been positively established that the
high-voltage filter capacitors have been discharged to a known safe level.
WARNING: Safety Ground
Improper grounding of this equipment can result in electric shock. The
TWTA must be operated only with a line cord with a safety ground wire.
It is the user's responsibility to ascertain that the power connector is
properly wired and that the power outlet is grounded.
WARNING: Explosive Atmosphere
To avoid explosion, never operate this TWTA in an explosive atmosphere.
This equipment is not certified for operation in an explosive atmosphere.
3.2 INSTALLATION
3.2.1 Unpacking
Upon receiving the TWTA, unpack the unit and inspect it for obvious signs of external damage. If damage is
observed, notify the carrier and contact an authorized service representative.
Save and store the shipping container in case the unit needs to be returned in the future for calibration or
repair.

Models 200T18G26z5A/200T26z5G40A
Rev – 8
3.2.2 Mounting
The TWTA may be operated as a standalone bench top unit or it may be installed in a 19" rack.
If rack mounting is desired, first remove the amplifier from the cabinet, then install the amplifier in the rack.
CAUTION:
Due to the weight of the unit, the removal of the amplifier from the
cabinet or rack is a two-person operation.
Before removal disconnect power, RF, and any other interface connectors. On the rear of the unit, remove the
six screws used to connect brackets to amplifier. On the front of the unit, remove the four screws holding
each the front panel to the cabinet. Carefully slide the amplifier out of the front of the cabinet.
CAUTION:
Never rack mount the TWTA using the front panel alone. The chassis is
likely to be damaged unless its weight is supported. Bottom support rails
must be provided in a rack mount configuration.
See Figure 3-1 for the locations of threaded holes on the bottom half of the TWTA chassis, which may be
used for supplementary support of the TWTA.
Figure 3-1. Rack Mounting Configuration
If bottom supports are used for rack mount installation of multiple units, the amplifiers should be separated
vertically by at least 1 3/4 inches. This will allow room for necessary support rails and facilitate installation
and removal of the units.

Models 200T18G26z5A/200T26z5G40A
Rev – 9
3.2.3 Cooling Requirements
The TWTA is provided with two cooling fans. It is important that air movement around the rear of the unit
be unobstructed.
CAUTION:
For either bench or rack mounting, do not position the TWTA in such a
way that the air intakes or outlets are blocked, or that the exhaust flows
are directed into the intakes. See Paragraph 3.5 for location of air intakes
and air outlets. If the unit is rack mounted, make sure that the intake air
is 45°C or below. If necessary, fabricate short ducts to direct the hot
exhaust air out of the rack enclosure. Great care must be taken to
minimize any flow restrictions. Avoid mounting heat-producing
equipment in the same rack, especially below the TWTA. Failure to
provide adequate cooling can result in the unit's shutting down from over
temperature conditions.
The TWTA dissipates approximately 1500 watts when in the operate mode.
3.2.4 AC Line Power Connections
The AC line power connection to the TWTA is made at the AC inlet J1, which is a female IEC-320 16A
connector. The power inlet receptacle is provided with a clamp that can be used to secure the mating plug
from accidental withdrawal. A line cord with AC plug suitable for the type of AC outlet used and consistent
with local electrical codes must be used to mate with J1. Minimum wire size recommended for the line cord
is 1.5 mm² (16 AWG).
Units are provided with an un-terminated 3-wire cord. To use this line cord it should be terminated with a
suitable plug to a 190 to 260 VAC 50-60 Hz. single-phase source as follows:
Color Function
International Harmonized North American
Brown Black Line
Blue White Neutral
Yellow/Green Green Safety Ground
CAUTION:
Connect plug to J1 and secure plug with bracket only when no AC is
supplied to the cord.
3.2.5 RF Output Connections
The RF output connection is a WR-42 waveguide flat flange in the 200T18G26z5A. The RF output
connection is a WR-28 waveguide flat flange in the 200T26z5G40A. Output flange alignment is critical for
proper operation. Align the two flanges and secure the mating waveguide while maintaining flange
alignment.

Models 200T18G26z5A/200T26z5G40A
Rev – 10
CAUTION:
Never operate the TWTA without a matched output load rated for at
least 300 watts, continuous. Full reflected power may irreparably
damage the TWT. Even with no drive, “looping” oscillation can result in
RF output high enough to damage the tube if it is operated without a
load. The VSWR detection, isolator and foldback circuit is provided to
protect the tube from progressive failure or mismatch of the output load;
it should not be relied on for protection from the absence of a load.
If an external isolator is installed at the output of the TWTA, either the isolator should have a load capable of
dissipating the full output of the TWTA or the isolator load should be provided with a temperature sensing
switch. The temperature switch should be normally closed, self-resetting, and with a temperature rating such
that there is no possibility of damaging the load by overheating before the switch opens. The TWTA may be
interlocked with the switch by connecting it between pins 3 and 4 of the external interlock connector (J2). If
no external isolator is used, install a jumper between pins 3 and 4. See section 3.2.6, External Interlock
Connector, below.
3.2.6 External Interlock Connector
The TWTA is provided with an external interlock capability via a 15-pin female D-sub connector, J2. To
enable the high voltage power supply, it is necessary to provide continuity between J2 pins 3 and 4. If the
amplifier shuts down because the interlock was opened, it will be necessary to reset the system to return to
standby (see System shutdown screen in Section 3.4). There is an internal jumper between J2 pins 1 and 2; a
continuity check through these pins can be used to verify the presence of the amplifier in the instrumentation
system. Users may adopt this interlock feature to disable the RF output for either equipment protection or as
a backup for personnel protection.
Pin Title Function
1 INTERNAL JUMPER Internal jumper from pin 1 to pin 2
2. INTERNAL JUMPER Internal jumper from pin 1 to pin 2
3. EXTERNAL INTERLOCK
SUPPLY
Disables High Voltage power supply in continuity is opened from pin 3 to pin 4.
4.
EXTERNAL INTERLOCK
RETURN
Disables High Voltage power supply in continuity is opened from pin 3 to pin 4.
5-9. NOT USED
10. INHIBIT SUPPLY Disables RF power output if continuity is opened from pin 10 to pin 15.
11-14 NOT USD
15 INHINIT RETURN Disables RF power output if continuity is opened from pin 10 to pin 15.
CAUTION:
Do not rely on the external interlock for personnel protection. The intent
of the external interlock feature is to disable the RF output for equipment
protection. Use proper operating and safety procedures to insure that
power is removed for personnel safety.
3.2.7 External IEEE-488 Connector
The TWTA is provided with a standard IEEE-488 connector on the rear panel. If the TWTA is mounted in a
bench-top cabinet, the mating connector should be a straight-entry cable type, not a side-entry type.