PA DC Volts—Supply voltage of the RF power amplifier.
PA DC Amps—Transistor drain current for the RF power amplifier.
PA Temperature—Temperature of the RF power amplifier heatsink in degrees C.
Driver Supply Volts—Regulated 24 volt DC supply for the RF driver amplifier.
Voltmeter—Reads the voltage at a test point located on the front edge of the motherboard. A
test lead connected to this point can be used for making voltage measurements in the transmit-
ter. The test point is intended as a servicing aid; an alternative to an external test meter. Re-
member that the accuracy is only as good as the reference voltage used by the metering cir-
cuit. Servicing a fault affected by the reference affects the Voltmeter reading. The metering
scale is 0 to 199.9 volts.
In the translator configuration, you can read a relative indication of RF signal strength numeri-
cally in the Voltmeter setting.
3.9 Fault Indicators
Faults are indicated by a blinking red light as follows:
SWR—Load VSWR exceeds 1.5:1. ALC voltage is reduced to limit the reflected RF power.
Lock—Frequency synthesizer phase-lock loop is unlocked. This indicator normally blinks for
about five seconds at power turn-on. Whenever this light is blinking, supply voltages will be
inhibited for the RF driver stage as well as for the RF power amplifier.
Input—The automatic carrier-off circuit is enabled (see sections 2.11 and 2.12) and the ab-
sence of a program input signal has exceeded the preset time. (The circuit treats white or pink
noise as an absence of a program.)
PA DC—Power supply current for the RF power output amplifier is at the preset limit. ALC
voltage has been reduced, reducing the PA supply voltage to hold supply current to the preset
limit.
PA Temp—PA heatsink temperature has reached 93° C (199° F).
At about 97°C (207° F), ALC voltage begins to decrease, reducing the PA supply voltage to
prevent a further increase in temperature. By 105° C (221° F) the PA will be at the minimum
output level, of approximately 190 Watts.
3-8 FM600 User’s Manual
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