12/20/11
888-2595-001
5-23
WARNING: Disconnect primary power prior to servicing.
Section 5 Maintenance and Alignments
ZX Series
STEP 15
Re-insert PA module and verify individual PA module currents remain
roughly equal under both pre-fault and post-fault conditions.
STEP 16
Procedure complete.
5.4.6
APC Setup for Multiple PA Chassis
This procedure clarifies the setup and alignment of the APC power control for ZX7.5
and higher power models. This alignment procedure is typically performed in the
factory and need not be repeated in the field unless a long term change to the desired
transmitter power level is required. This procedure should only be attempted if all PA
modules operational and with all PA chassis fully warmed up.
The general principles at work are the same as in the alignment of a single-chassis
model, but there is the added element of there being two or more APC circuits operating
in parallel. Each chassis is adjusted one at a time with a procedure that mirrors the
single-chassis case, with the exception that one PA chassis is adjusted for 100% power,
while the other is adjusted for 90% power. This ensures that the transmitter power will
always follow the APC circuit at 100% and behave as if only a single APC loop were
present. The 90% APC circuit remains in reserve and will only become active if the
first APC circuit fails or its chassis (only) is switched off.
STEP 1
Verify all PA modules are operational and transmitter has been operating
at significant power for at least one half hour to reach a thermal steady
state.
STEP 2
Place both PA chassis in REMOTE DISABLED mode via toggle
switches on their respective controller cards.
STEP 3
Switch off lower PA chassis via its front panel OFF button.
STEP 4
Adjust upper PA chassis to ½ of desired total transmitter power level.
(e.g. adjust to 5kW for a desired 10kW total power level) using
appropriate adjustment procedure in Section 5.4.4 or 5.4.5. Limit
exciter power when directed to do so in procedure. Measure power
using PA chassis front panel meter, not system metering assembly
forward meter.
STEP 5
Switch off upper PA chassis and switch on lower PA chassis via their
respective ON and OFF buttons.
STEP 6
Adjust lower PA chassis to 90% of setting for upper PA chassis (e.g.
adjust to 4.5kW instead of 5kW as previously) using appropriate
adjustment procedure in Sections.5.4.4 or 5.4.5. It is not necessary to re-
adjust exciter power when directed to do so in procedure. Measure
Summary of Contents for ZX2500
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