AR 10044005, Operating And Service Manual

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Model 5000A225A
Rev B 51
4.4.2 Module Replacement
If, after troubleshooting, it has been determined that one of the Liquid-cooled modules has failed, the
following procedure should be followed if a spare module for the unit is available.
CAUTION:
Power to the unit must be turned off before performing any repair work;
this should be done by unplugging the unit from the line voltage source.
Failure to disconnect the unit from the line voltage source prior to
servicing would present a hazard to service personnel and could result in
damage to the amplifier.
Before pulling out the MPA, MPA-retaining hardware must be removed. Removal from the cabinet requires
the removal of a mechanical stop. Also, cables and connectors must be disconnected. Side panels or the top
panels may need to be removed. Providing that the filler caps for the liquid coolant are left in place, the unit
may be turned on its side or on its top for service.
After cover removal, the signal connector, the two heavy DC power supply connectors and the RF input and
output connectors can be disconnected from the module being serviced. The liquid coolant connectors will not
spill coolant and may be disconnected along with the other connections. Take note of any connector that is
found loose. To remove the module, remove the six screws that hold the module into the frame and gently lift
the module out. The module is relatively heavy with its copper cold plate. Be careful not to damage wires or
RF cables, and not to hold the module by its magnetic cores, during the removal process. Be especially
careful with SMT components that may be location along the edge of the PWB.
A module is installed in the reverse order, making sure that all connections are tight. Use an appropriate open-
end wrench to tighten the SMA RF connector.
4.4.3 Cooling System
The liquid cooling system is a closed system which will operate for years without maintenance. The coolant
level should extend into the coolant reservoir, with the heat exchanger full for optimum cooling. The coolant
is a mixture of 50% Noburst AL propylene-glycol anti-freeze and 50% distilled water. This will provide
protection to 5° F (-15° C) for operation and -20 ° F (-29° C) for storage. Quick-disconnect leak-proof
connectors are incorporated to allow removal of modules and major system components with no leakage of
fluid. If coolant is removed from the system for any reason, the pump should not be activated; damage to the
pump can occur if it is run without fluid.
CAUTION:
EYE AND SKIN IRRITANT
Contains propylene glycol. Do not swallow. Do not allow eye contact or
prolonged skin contact. For additional information, refer to Material
Safety Data Sheet.