5-20 888-2595-001 12/20/11
WARNING: Disconnect primary power prior to servicing.
Section 5 Maintenance and Alignments
ZX Series
Tools required:
Small adjustment screwdriver
STEP 1 Verify current operating mode is FM based on amplifier front panel
STATUS LED display.
STEP 2 Open amplifier front door and locate POWER RAISE pushbutton on
controller board upper edge.
STEP 3 Depress POWER RAISE pushbutton repeatedly until power adjustment
circuit has clearly reached top of its range.
STEP 4 Lower exciter power to half its normal value as a safety precaution.
STEP 5 Locate POWER LIMIT – FM potentiometer on transmitter controller
board upper edge and dial fully clockwise. FORWARD POWER LOW
alarm LED should light, if not already lit before.
STEP 6 Increase exciter power to achieve 103%-105% of desired power level.
STEP 7 Dial POWER LIMIT – FM potentiometer counter-clockwise to lower
power to 100% of desired power level.
STEP 8 Verify FORWARD POWER LOW alarm LED has extinguished on
controller board.
STEP 9 Increase exciter output power 10% beyond previous setting to ensure
transmitter APC has 10% gain reserve margin. Transmitter output
power should not change as exciter power is increased.
STEP 10 Actuate controller board POWER RAISE and LOWER pushbuttons to
verify it is possible to adjust power over a <10% to 100% range.
STEP 11 Note exciter power level on exciter power meter for future reference.
STEP 12 Remove one PA module and adjust APC IDLE potentiometer to return
individual currents of remaining PA modules to pre-fault levels, as
measured with front panel meter PA AMPS position and PA MODULE
CURRENTS pushbuttons.
This adjustment is typically performed at the highest gain channel (only) for fre-
quency-agile N+1 applications.
STEP 13 Re-insert PA module and verify individual PA module currents remain
roughly equal under both pre-fault and post-fault conditions.
STEP 14 Procedure complete.
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