BIRD Termaline 8920 Series User manual

Termaline®Load Resistor
Series 8920
Operation Manual
©Copyright 2016 by Bird Technologies, Inc.
Instruction Book Part Number 920-8920S Rev. H
Termaline® and Thruline® are Registered Trademarks
of Bird Electronic Corporation

i
Safety Precautions
The following are general safety precautions that are not necessarily related to any specific part or procedure, and
do not necessarily appear elsewhere in this publication. These precautions must be thoroughly understood and
apply to all phases of operation and maintenance.
WARNING
Keep Away From Live Circuits
Operating Personnel must at all times observe general safety precautions. Do not replace
components or make adjustments to the inside of the test equipment with the high
voltage supply turned on. To avoid casualties, always remove power.
WARNING
Shock Hazard
Do not attempt to remove the RF transmission line while RF power is present.
WARNING
Do Not Service Or Adjust Alone
Under no circumstances should any person reach into an enclosure for the purpose of
service or adjustment of equipment except in the presence of someone who is capable of
rendering aid.
WARNING
Safety Earth Ground
An uninterruptible earth safety ground must be supplied from the main power source to
test instruments. Grounding one conductor of a two conductor power cable is not
sufficient protection. Serious injury or death can occur if this grounding is not properly
supplied.
WARNING
Resuscitation
Personnel working with or near high voltages should be familiar with modern methods of
resuscitation.
WARNING
Remove Power
Observe general safety precautions. Do not open the instrument with the power on.

Safety Precautions
ii
Safety Symbols
Note: Calls attention to supplemental information.
Warning Statements
The following safety warnings appear in the text where there is danger to operating and maintenance personnel,
and are repeated here for emphasis.
See page 3, 4, 7, and 10.
See page 5, 7, 8, and 9.
See pages 8 and 10.
See page 8, 10, and 11.
WARNING
Warning notes call attention to a procedure, which if not correctly performed, could result
in personal injury.
CAUTION
Caution notes call attention to a procedure, which if not correctly performed, could result
in damage to the instrument.
This symbol indicates that a shock hazard exists if the precautions in the
instruction manual are not followed.
The caution symbol appears on the equipment indicating there is
important information in the instruction manual regarding that particular
area.
This symbol indicates that the unit radiates heat and should not be
touched while hot.
WARNING
The vent plug must be used at all times when the unit is operating or cooling.
Failure to do so could result in an explosion or severe burns.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF
power is being applied. Leaking RF energy is a potential health hazard.
WARNING
Disconnect the unit from all power sources before servicing.
The unit may be energized from multiple sources.
The potential for electric shock exists.
WARNING
Oil is slippery. If a leak occurs, be careful not to fall.

Termaline® Load Resistor
iii
Caution Statements
The following equipment cautions appear in the text and are repeated here for emphasis.
See page 3.
See page 4.
See page 4.
See page 10.
CAUTION
This load is designed for operation in a horizontal position only, with the vent plug up. Do
not use in any other manner.
CAUTION
Do not contaminate the coolant with pipe sealant.
CAUTION
If installed, connect optional interlock before applying RF power.
CAUTION
Use only Bird coolant, P/N 5-1070, to prevent damage to the load.

Safety Precautions
iv
Safety Statements
USAGE
ANY USE OF THIS INSTRUMENT IN A MANNER NOT SPECIFIED BY THE MANUFACTURER MAY
IMPAIR THE INSTRUMENT’S SAFETY PROTECTION.
USO
EL USO DE ESTE INSTRUMENTO DE MANERA NO ESPECIFICADA POR EL FABRICANTE, PUEDE
ANULAR LA PROTECCIÓN DE SEGURIDAD DEL INSTRUMENTO.
BENUTZUNG
WIRD DAS GERÄT AUF ANDERE WEISE VERWENDET ALS VOM HERSTELLER BESCHRIEBEN,
KANN DIE GERÄTESICHERHEIT BEEINTRÄCHTIGT WERDEN.
UTILISATION
TOUTE UTILISATION DE CET INSTRUMENT QUI N’EST PAS EXPLICITEMENT PRÉVUE PAR LE
FABRICANT PEUT ENDOMMAGER LE DISPOSITIF DE PROTECTION DE L’INSTRUMENT.
IMPIEGO
QUALORA QUESTO STRUMENTO VENISSE UTILIZZATO IN MODO DIVERSO DA COME
SPECIFICATO DAL PRODUTTORE LA PROZIONE DI SICUREZZA POTREBBE VENIRNE
COMPROMESSA.

Termaline® Load Resistor
v
SERVICE
SERVICING INSTRUCTIONS ARE FOR USE BY SERVICE - TRAINED PERSONNEL ONLY. TO AVOID
DANGEROUS ELECTRIC SHOCK, DO NOT PERFORM ANY SERVICING UNLESS QUALIFIED TO DO
SO.
SERVICIO
LAS INSTRUCCIONES DE SERVICIO SON PARA USO EXCLUSIVO DEL PERSONAL DE SERVICIO
CAPACITADO. PARA EVITAR EL PELIGRO DE DESCARGAS ELÉCTRICAS, NO REALICE NINGÚN
SERVICIO A MENOS QUE ESTÉ CAPACITADO PARA HACERIO.
WARTUNG
ANWEISUNGEN FÜR DIE WARTUNG DES GERÄTES GELTEN NUR FÜR GESCHULTES
FACHPERSONAL.
ZUR VERMEIDUNG GEFÄHRLICHE, ELEKTRISCHE SCHOCKS, SIND WARTUNGSARBEITEN
AUSSCHLIEßLICH VON QUALIFIZIERTEM SERVICEPERSONAL DURCHZUFÜHREN.
ENTRENTIEN
L’EMPLOI DES INSTRUCTIONS D’ENTRETIEN DOIT ÊTRE RÉSERVÉ AU PERSONNEL FORMÉ AUX
OPÉRATIONS D’ENTRETIEN. POUR PRÉVENIR UN CHOC ÉLECTRIQUE DANGEREUX, NE PAS
EFFECTUER D’ENTRETIEN SI L’ON N’A PAS ÉTÉ QUALIFIÉ POUR CE FAIRE.
ASSISTENZA TECNICA
LE ISTRUZIONI RELATIVE ALL’ASSISTENZA SONO PREVISTE ESCLUSIVAMENTE PER IL
PERSONALE OPPORTUNAMENTE ADDESTRATO. PER EVITARE PERICOLOSE SCOSSE
ELETTRICHE NON EFFETTUARRE ALCUNA RIPARAZIONE A MENO CHE QUALIFICATI A FARLA.

Safety Precautions
vi
CONNECT INTERLOCK TO TRANSMITTER/GENERATOR/AMPLIFIER BEFORE OPERATING.
BRANCHER LE VERROUILLAGE À L’ÉMETTEUR/GÉNÉRATEUR/AMPLIFICATEUR AVANT EMPLOI.
CONECTE EL INTERBLOQUEO AL TRANSMISOR/GENERADOR/AMPLIFICADOR ANTES DE LA
OPERACION.
VOR INBETRIEBNAHME VERRIEGELUNG AM SENDER/GENERATOR/VERSTÄRKER
ANSCHLIESSEN.
PRIMA DI METTERE IN FUNZIONE L’APPARECCHIO, COLLEGARE IL DISPOSITIVO DI BLOCCO AL
TRASMETTITORE/GENERATORE/AMPLIFICATORE.

Termaline® Load Resistor
vii
About This Manual
This manual covers the operating and maintenance instructions for the following models:
Changes to this Manual
We have made every effort to ensure this manual is accurate. If you discover any errors, or if you have suggestions
for improving this manual, please send your comments to our Solon, Ohio factory. This manual may be periodically
updated. When inquiring about updates to this manual refer to the part number and revision on the title page.
Chapter Layout
Introduction — Describes the features of the Bird Termaline, Semiconductor, RF Load Resistor lists equipment
supplied and optional equipment, and provides power-up instructions.
Theory of Operation — Describes how the Termaline, Semiconductor, RF Load Resistor works and its functions.
Installation — Describes the how to install the Termaline, Semiconductor, RF Load Resistor.
Operation with Blower — Describes procedures require for operating the load resistor equipped with a blower
unit.
Maintenance — Lists routine maintenance tasks as well as troubleshooting for common problems. Specifications
and parts information are also included.
8921 8922 8926 8927
8928 8922D 8926D 8927D

viii
Table of Contents
Safety Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i
Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Warning Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Caution Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Safety Statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
About This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Changes to this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Chapter Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Chapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Items Supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Items Required but not Supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Optional Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 2 Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Coolant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Thermal Interlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Chapter 3 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Unpacking and Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Installing Thermoswitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Interlock Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Connecting RF Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Chapter 4 Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Normal Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Operation Under Abnormal Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Emergency Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Chapter 5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
RF Assembly Resistance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Coolant Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
RF Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Load Resistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Storage and Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Customer Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Available “QC” Type Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Limited Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1
Chapter 1 Introduction
Bird 8920 Series Loads are portable, 50 ohm, coaxial RF transmission line terminations, designed for frequency
ranges of DC – 1 GHz. Bird 8920D Series Loads are identical, except that they are designed for the UHF (470 – 860
MHz) band. They provide accurate, dependable, and low reflection line terminations. Up to 5000 watts of RF power
can be dissipated.
The load has a coolant chamber surrounded by radiator fins. The front and rear fins form mounting flanges which
can be used as supports for freestanding use or as brackets for fixed mounting. A vent plug at the top of the unit
relieves internal pressure from coolant expansion. The load’s simple and rugged design minimizes maintenance
requirements.
Items Supplied
Load Resistor: Pre-filled with coolant at the factory
One Shipping Plug
One Vent Plug
Instruction Manual
Items Required but not Supplied
Coupling Kit: Connects the load to the RF line
Optional Accessories
Interlock Thermoswitch: Automatically shuts off the transmitter to prevent overheating of the load
Figure 1 Bird 8920 Series Outline Drawing

2
Chapter 2 Theory of Operation
Load Resistor
Bird 8920 series loads consist of a thin-film-on-ceramic resistor immersed in a dielectric coolant. The resistor,
individually selected for its accuracy, is enclosed in a special housing. When surrounded by the coolant, this
produces a uniform, practically reflectionless line termination over the specified frequencies.
Coolant
The load is cooled by natural fluid and air convection currents. The coolant, chosen for its dielectric and thermal
characteristics, carries heat from the resistor to the walls of the cooling tank, where radiator fins surrounding the
tank transfer the heat to the air.
When the coolant is heated, thermal expansion causes an increase in the internal pressure. The vent plug relieves
this pressure while protecting the opening from dirt or other contaminants.
Thermal Interlock
Loads can be supplied with an optional passive over-temperature thermoswitch. Normally closed, it opens at the
maximum safe load temperature of 236 °C (457 °F), turning off transmitter power. The interlock system will not
permit use of the transmitter until the load has reached a safe temperature.

3
Chapter 3 Installation
This chapter provides information for on-site requirements, unpacking, inspection, and preparing the load for use.
Unpacking and Inspection
1. Carefully inspect shipping container for signs of damage.
If the shipping container is damaged, do not unpack the unit. Immediately notify the shipping carrier and
Bird Technologies.
If the shipping container is not damaged, unpack the unit. Save shipping materials for repackaging.
2. Inspect unit for visual signs of damage.
Note: If there is damage, immediately notify the shipping carrier and Bird Technologies.
Mounting
Place the load in a dry, dust and vibration free environment. Do not use outdoors or in areas of condensing
humidity. Allow at least 12" (30 cm) of clearance on all sides of the load.
The load is equipped for either portable use or fixed installation. The mounting brackets on the front and rear faces
have four mounting slots arranged in a 412" x 14732" rectangle (114.3 x 361.2 mm). Use a screw with a 38" (9.53
mm) diameter max.
CAUTION
This load is designed for operation in a horizontal position only, with the vent plug up.
Do not use in any other manner.
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do
so could result in an explosion or severe burns.

Installation
4
Setup
Note: Before first using the load, get a resistance baseline for future maintenance. Refer to "RF
Assembly Resistance Test" on page 9 for details.
1. Remove the shipping plug.
2. Install the vent plug. Refer to Figure 1 .
Installing Thermoswitch
Bird 8920 series loads can be equipped with an optional interlock thermoswitch, P/N 8890-008. It is normally
closed, opening at 236 °C (457 °F), with a rating of 10A @ 120 VAC and 5A @ 230 VAC.
1. Stand the unit on its front, supporting it so that the connector is not damaged.
Note: In this position there is no danger of the coolant pouring out through the socket plug hole.
2. Remove the socket plug just above the connector assembly, using a 916" hex wrench.
3. Replace the plug with the thermoswitch.
4. Apply pipe sealing compound, sparingly, to the external threads, only, of the thermoswitch.
5. Check for coolant leaks upon completion.
6. Remove the shipping plug. Install the vent plug.
Interlock Connection
Note: Connect the thermoswitch to the interlock as follows (see Figure 2 ):
1. Unscrew the large knurled ring-nut (A) at the lower end of the coupling jack assembly.
2. Pull it off the thermoswitch jack (B).
3. Unscrew the small knurled cover fitting from the base plug (D) of the connector to release the base.
4. Thread the control switch wires through the clamp (E) with the washers (F) inside and with its threaded fitting
in place.
5. Service the control switch wire with short tips and put spaghetti sleeves over the wire ends if necessary.
6. Securely solder the control switch leads to the lugs (G) of the connector base.
Note: The ring-nut (A) must be in place over the base plug (D) with the knurled end facing out.
7. Screw on the cover ring, then fasten the cable clamp (E) in place and tighten both yoke screws (H).
8. Put the plug back on the thermoswitch and tighten the nut (A).
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do
so could result in an explosion or severe burns.
CAUTION
Do not contaminate the coolant with pipe sealant.
CAUTION
If installed, connect optional interlock before applying RF power.

Termaline® Load Resistor
5
Figure 2 Thermoswitch Assembly
Connecting RF Power
After installing the load, the RF transmission line can be attached using standard coaxial line coupling kits.
“QC” Connector Coupling
Use 50 ohm coaxial cable such as RG-218/U or -220/U (-17A or -19A), appropriate for the frequency and
power level of operation.
Use a cable connector which will mate with the one on the load.
Swivel Flanged Coupling
Note: To couple the swivel flange with a flanged RF transmission line, use an appropriate coupling kit.
1. Insert the center bullet.
2. Push it in until it is fully seated.
3. Connect the coaxial input in a straight line.
4. Push carefully on the center conductor to close.
Note: The swivel flange on the load makes connection independent of the orientation of the fixed
flange on the coaxial input outer conductor.
5. Insert the bolt sets and tighten evenly all around to transmission line manufacturer’s recommended torque.
6. Use all of the bolts.
Figure 3 Swivel Flanged Coupling
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF
power is being applied. Leaking RF energy is a potential health hazard.

Installation
6
Unflanged Coupling
Note: To couple the unflanged connector with an unflanged RF line, use an appropriate coupling kit.
Refer to Figure 4 while following the instructions below:
1. Insert the center bullet and bottom it on the midpoint nibs.
2. Position the outer sleeve, with clamping bands, over the input connector.
3. Set the transmission line snugly against the coupling stops.
4. Position the clamping bands evenly about 3/4” from the ends of the sleeve.
5. Tighten the clamping bands.
Figure 4 Unflanged Coupling

7
Chapter 4 Operating Instructions
Normal Operation
Bird 8920 series loads have no indicators or operating controls. They require no special operating procedures or
surveillance when their performance limits are not exceeded. Follow the instructions for the specific transmitter
equipment.
Operation Under Abnormal Conditions
The load can be subjected to moderate overloads for short periods. If this is likely, make sure the interlock is
properly connected to prevent damage to the load.
Shutdown
These loads are passive devices, so have no way of being turned off. Turn off RF power at the source.
Emergency Shutdown
Turn off RF power at the source.
If the interlock thermoswitch is properly connected, RF power will be automatically turned off when the coolant
temperature reaches an unsafe level.
WARNING
The vent plug must be used at all times when the unit is operating or cooling.
Failure to do so could result in an explosion or severe burns.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF
power is being applied. Leaking RF energy is a potential health hazard.

8
Chapter 5 Maintenance
This chapter covers cleaning, inspection, trouble-shooting, and specifications for the Bird 8920 series loads.
Troubleshooting
The table below contains troubleshooting information for problems which can occur during normal operation. This
manual cannot list all malfunctions that may occur, or their corrective actions. If a problem is not listed or is not
corrected by the listed actions, notify a qualified service center.
Maintenance
Cleaning
The outside surface of the instrument should be wiped free of dust and dirt when necessary. Excessive dust on the
cooling fins will interfere with heat dissipation. Clean the RF connector, both metallic and insulating surfaces, with a
dry, non-residue forming solvent.
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF
power is being applied. Leaking RF energy is a potential health hazard.
WARNING
Disconnect the unit from all power sources before servicing.
The unit may be energized from multiple sources.
The potential for electric shock exists.
WARNING
Oil is slippery. If a leak occurs, be careful not to fall.
Problem Possible Cause Correction
Leaking coolant Loose clamping band Tighten the clamping band
Defective or improperly installed O-
ring
Replace the O-ring
(See
"Load Resistor" on page 11 )
High or low DC resistance Loose RF input connector Tighten connector
Faulty RF input connector Model 8921: Replace connector
(See
"RF Connector" on page 10 )
All other models: Return the unit for service
Faulty resistor Replace the resistor
(See
"Load Resistor" on page 11 )
Overheating radiator RF power too high Lower RF power
Coolant level too low Check the coolant level. Add coolant if necessary
(See
"Coolant Level" on page 10 )
Coolant degraded Replace the coolant
(See
"Coolant Level" on page 10 )
Faulty resistor Replace the resistor
(See
"Load Resistor" on page 11 )
WARNING
Oil is slippery. If a leak occurs, be careful not to fall.

Termaline® Load Resistor
9
Inspection
Inspect the unit every six months. Check for coolant leakage around the clamping band and the thermoswitch. Also
check for corrosion.
RF Assembly Resistance Test
Note: These tests are by no means a necessity to the operation of the load but merely guidelines for
the users information.
Accurate measurement of the DC resistance between the inner and outer conductors of the RF input connector will
provide a good check of the condition of the load resistor.
Checking the DC resistance is simply used to measure a change in the resistance over time. Tracking the DC
resistance should start before the unit is first put into service. Perform the following steps and record the value for
future comparison. The resistor should provide at least 5,000 hours of operation before requiring any additional
service. DC resistance should be measured annually.
Preparation:
Tools: Common hand tools.
Ohmmeter with an accuracy of ± 1% at 50 ohms (or use a resistance bridge).
Use low resistance leads, preferably a short piece of 50 ohm coaxial cable fitted with an appropriate
connector or alligator clips.
Temperature of the load should be stabilized between 20°C to 25°C (68°F to 77°F).
DC Resistance Measurement
Note: It is recommended that this resistance check be performed each time the load is to be used.
1. Turn off RF power and interlock circuitry before making any disconnections.
2. Disconnect the RF coaxial line.
3. Connect the multimeter test leads across the center and outer conductor of the load resistor. See Figure 5 .
4. Record the value of the resistance before the load is put into service. Compare subsequent values with the
latest reading. If the values vary more than 2 ohms this could be an indication of a failing resistive element.
Figure 5 Measuring DC Resistance
WARNING
Never attempt to connect or disconnect RF equipment from the transmission line while RF
power is being applied.
Leaking RF energy is a potential health hazard.

Maintenance
10
Coolant Level
Coolant lifetime will vary greatly depending on operating conditions. For heavy use (full RF power for long times,
high ambient temperature), check the coolant every 500 hours. If the load has only had light duty (fraction of full
power, low ambient temperature), then coolant inspection may only be necessary every 2,000 hours.
Note: Correct any coolant leakage before inspection. (See "Troubleshooting" on page 8 )
1. Remove the load resistor (Refer to “Load Resistor” on page 18).
2. Ensure the coolant should be clear, with a faint yellow tinge, and have a slightly sweet smell.
3. Do the following ff the coolant is black with a burnt or acrid smell:
a. Drain it
b. Add about 6.7 gal (25.2 L) of coolant.
Note: With the load still on end, the coolant level should be 434" (125 mm) below the top surface of
the resistor assembly mounting ring, at ambient temperature.
4. Add coolant if necessary.
Repair
RF Connector
The Model 8921, only, has a special Bird “QC” connector which allows easy changing of the RF connector. This does
not disturb the coolant seal or affect the electrical continuity of the load. To change the connector, proceed as
follows:
1. Remove the four screws at the corners of the RF connector.
2. Pull the connector straight out.
3. Push the new connector in.
4. Ensure that the center pin on the connector is properly seated in the mating socket on the load.
5. Replace the screws.
Note: If not using the connector normally supplied, frequency and power must be limited to the capa-
bilities of the connector.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized
from multiple sources.
The potential for electric shock exists.
WARNING
Oil is slippery. If a leak occurs, be careful not to fall.
CAUTION
Use only Bird coolant, P/N 5-1070, to prevent damage to the load.
WARNING
Disconnect the unit from all power sources before servicing. The unit may be energized
from multiple sources.
The potential for electric shock exists.
WARNING
The vent plug must be used at all times when the unit is operating or cooling. Failure to do
so could result in an
explosion or severe burns.

Termaline® Load Resistor
11
Load Resistor
1. Remove the vent plug.
2. Install the shipping plug.
3. Stand the unit on its back with the connector end up.
Note: Support the unit to prevent damage to the interlock
Note: In this position there is no danger of the coolant pouring out through the resistor hole.
4. Unscrew and remove the clamping band.
5. Lift the load resistor assembly out of the tank.
6. Allow any coolant to drip back into the tank.
Note: The O-Ring should be free of twists and positioned evenly around the flange of the resistor
housing. If it shows signs of deterioration (e.g. is no longer pliable or has surface cracks) replace it.
7. Replace the entire load resistor assembly.
Note: It cannot be further disassembled.
8. Put the clamping band in place and tighten it.
9. Remove the shipping plug. Install the vent plug.
Storage and Shipment
Cover the load before storing to keep out dust and dirt. It is not necessary to install the shipping plug. Store in a dry,
dust-free environment where the ambient temperature will remain between
–40 and +45 °C (–40 to +113 °F).
To ship the load, take the following precautions:
1. Remove the vent plug and replace it with the shipping plug.
2. Wrap the vent plug with padding.
3. Tape it to the side of the load for protection.
Note: With the shipping plug installed, it is not necessary to empty out the coolant.
4. Wrap the connector in padding.
5. Pack and brace the load in a sturdy wooden crate for shipment.
Customer Service
Any maintenance or service procedure beyond the scope of those in this chapter should be referred to a qualified
service center.
If the unit needs to be returned for any reason, request an Return Material Authorization (RMA) through the Bird
Technologies website. All instruments returned must be shipped prepaid and to the attention of the RMA number.
Bird Service Center
30303 Aurora Road
Cleveland (Solon), Ohio 44139-2794
Fax: [phone]
E-mail: [e-mail]
For the location of the Sales Office nearest you, visit our Web site at:
http://www.birdrf.com
WARNING
Oil is slippery. If a leak occurs, be careful not to fall.