Broadcast Electronics FM-5T, User Manual

Page: 165 / 191

2-11
WARNING: DISCONNECT POWER PRIOR TO SERVICING
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
2-118. Disconnect the transmitter primary power.
2-119. Remove the test equipment and replace the reflected power directional coupler. Ensure the
reflected power directional coupler arrow is down (
↓
). Ensure cable 131 is re-connected to
the reflected power directional coupler port.
2-120.
AM NOISE TEST RECEPTACLE CALIBRATION.
Potentiometer R27 calibrates the signal
at the AM noise test receptacle. Adjustment is required only if repairs have been made to
the AM noise circuitry. To adjust the control, proceed as follows.
2-121. Required Equipment. The following equipment is required to adjust the AM noise calibra
tion control.
A. 1/16 inch jewelers screw-driver, flat-tip.
B. Digital multimeter (Fluke 77 or equivalent).
2-122. Procedure. To adjust the control, proceed as follows.
2-123. Check and adjust output power meter calibration control R113 before proceeding (refer to
OUTPUT POWER METER CALIBRATION in the preceding text).
2-124. Disconnect the transmitter primary power.
2-125. Connect the multimeter between the center conductor of the AM noise test receptacle and
chassis ground.
2-126. Apply power and operate the transmitter in the local manual mode ( REMOTE DISABLE
illuminated, APC ON extinguished) at the desired 100% RF power output as indicated by
the front panel OUTPUT POWER meter.
2-127. Refer to Figure 2-1 and adjust AM noise calibration control R27 for a 1.09 volt dc indica
tion on the multimeter.
2-128. Disconnect the transmitter primary power.
2-129. Remove the test equipment and return the transmitter to service.
2-130.
IPA FORWARD POWER CALIBRATION.
Potentiometer R95 calibrates the IPA forward
power sample circuit. This circuit is not used in an FM-5T/FM-5TS.
2-131.
CONTROLLER RESET.
The controller is equipped with reset switch SW3. However, the
microcontroller is equipped with a circuit to automatically reset the processor in the event
of a lock-up condition. As a result, the switch will typically not be used.
2-132.
CUSTOMER ADJUSTMENTS - RESET.
The customer adjustments and the 100% power
programming can be reset to the factory defaults if required. The reset operation is re
quired only if the customer adjustments have been mis-adjusted. To reset the controller
programming to the factory defaults, proceed as follows:
1. Depress the HIGH VOLTAGE OFF switch/indicator.
2. Refer to Figure 2-1 and remove the model programming jumpers from model
programming header J8.
3. Refer to Figure 2-1 and re-install the model programming jumpers. Ensure the
jumpers are correctly programmed for the transmitter model.