Broadcast Electronics FM-5T, User Manual

Page: 159 / 191

2-5
WARNING: DISCONNECT POWER PRIOR TO SERVICING
CAUTION
CAUTION
THE OVERLOAD THRESHOLD LEVEL ADJUSTMENTS
DETERMINE WHEN THE TRANSMITTER INITIATES
ACTION. IF A CONTROL IS INCORRECTLY ADJUSTED
THE CONTROLLER MAY NOT SENSE THE FAULT AND
DAMAGE TO THE TRANSMITTER MAY RESULT.
2-28. Procedure. To adjust the threshold level of the plate overload circuit, proceed as follows:
2-29. Apply power and operate the transmitter within specifications at the rated RF output into
a proper 50 Ohm load. Record the OUTPUT LOADING control cyclometer indication
.
2-30. Refer to Figure 2-1 and select PLATE OVERLOAD as follows:
1. Operate customer adjustment function switch SW1 to position 5.
2. Depress and hold customer adjustment up/down switch S2 in the up position
to raise the threshold.
2-31. Operate the APC ON switch/indicator to extinguish the switch/indicator.
2-32. Operate the OUTPUT LOADING control clockwise and the RAISE switch/indicator to
detune the transmitter until plate current is increased by 0.2 Amperes as indicated on the
PLATE CURRENT meter.
2-33. Refer to Figure 2-1 and use up/down switch S2 to lower the plate overload threshold until
the PLATE OVERLOAD indicator and the OVERLOAD RESET switch/indicator illumi
nate and the transmitter cycles off.
2-34. Depress the HIGH VOLTAGE OFF switch then depress and hold the LOWER switch/in
dicator for approximately four seconds.
2-35. Depress the OVERLOAD RESET and the HIGH VOLTAGE ON switch/indicators.
2-36. Observe the PLATE CURRENT meter and operate the RAISE switch/indicator until the
transmitter deenergizes. Correct adjustment is obtained when the transmitter deenergizes
and plate current is 0.2 amperes above normal. Repeat the procedure if required.
2-37. Depress the HIGH VOLTAGE OFF switch and OVERLOAD RESET switch/indicator.
2-38. Restore the OUTPUT LOADING control to the cyclometer indication recorded in the pre
ceding text and operate the APC ON switch/indicator to illuminate the switch/indicator.
2-39.
SCREEN OVERLOAD ADJUSTMENT.
The screen overload control can be adjusted from
100 mA to 190 mA. The factory default is 145 mA. To adjust the SCREEN overload
threshold, proceed as follows.
2-40. Required Equipment. The following equipment is required to adjust the screen overload
threshold.
A. Insulated adjustment tool, flat-tip (BE P/N 407-0083).
CAUTION
CAUTION
THE OVERLOAD THRESHOLD LEVEL ADJUSTMENTS
DETERMINE WHEN THE TRANSMITTER INITIATES
ACTION. IF A CONTROL IS INCORRECTLY ADJUSTED
THE CONTROLLER MAY NOT SENSE THE FAULT AND
DAMAGE TO THE TRANSMITTER MAY RESULT.
2-41. Procedure. To adjust the threshold level of the screen overload circuit, proceed as follows: