Set Transmitter Power Level (Case 1: Internal Transmitter Apc Control) - Harris ZX2500 Technical Manual

ZX Series
STEP 3
STEP 4
STEP 5
5.4.4 Set Transmitter Power Level (Case 1: internal
transmitter APC control)
Use this procedure when the transmitter power level is being controlled internally via
the IPA module bias voltage. This is typically the case when the ZX amplifier is being
used strictly for FM-only service.
NOTE:
If the type of power control is unknown, check the position of jumper JP3 on the
transmitter controller PC board: position 1-2 is internal control; position 2-3 is
external (exciter) control. In the case of external control, consult the alternate
procedure immediately following this one. The use of external power control is
almost exclusively reserved for use with the FlexStar HDX exciter operating in
HD, FM+HD, or tri-mode operation.
NOTE:
For ZX7.5 and ZX10 model transmitters, please also consult section 5.4.6 for
additional information on how to adjust the APC control circuits in both PA
amplifier chassis.
!
CAUTION:
IMPROPER ADJUSTMENT OF THIS CIRCUIT COULD RESULT IN DAMAGE TO THE
TRANSMITTER. THE TRANSMITTER COMES FROM THE FACTORY WITH THIS
ADJUSTMENT ALREADY PERFORMED. USE THIS PROCEDURE ONLY WHEN IT
BECOMES NECESSARY TO CHANGE PERMANENTLY THE TRANSMITTER OUTPUT
POWER LEVEL FROM THAT ESTABLISHED AT THE TIME OF IN-FACTORY TEST. IF
THE TRANSMITTER IS UNABLE TO REACH FULL POWER, RULE OUT ALL OTHER
CAUSES BEFORE PROCEEDING TO PERFORM THIS ADJUSTMENT.
NOTE:
It is typical for the gain of the PA modules to drop during the first half hour of
operation. This procedure should be performed after the transmitter has reached a
thermal steady state.
12/20/11
WARNING: Disconnect primary power prior to servicing.
If system meter reading is to be calibrated, calibrate reverse reading via
front panel REV trimmer potentiometer on system metering assembly
face to immediate left of meters.
Reverse any steps taken to create temporary high reverse power reading.
Procedure complete.
888-2595-001
Section 5 Maintenance and Alignments
5-19