3–8
FM30/100/250 User's Manual
PA DC Volts—Supply voltage of the RF power amplifier.
PA DC Amps—Transistor drain current for the RF power amplifier.
PA DC Temperature—Temperature of the RF power amplifier heatsink in degrees C.
Supply DC Volts—Unregulated DC voltage at the input of the voltage regulators.
For battery operation, this reading is the battery voltage minus a diode drop.
Voltmeter—Reads the voltage at a test point located on the front edge of the mother-
board. A test lead connected to this point can be used for making voltage measure-
ments in the transmitter. The test point is intended as a servicing aid; an alternative
to an external test meter. Remember that the accuracy is only as good as the refer-
ence voltage used by the metering circuit. Servicing a fault affected by the refer-
ence 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 numerically 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 absence 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 50° C (122° F) for the FM30 and
70° C (158° F)for the FM100 and FM250.
At about 55° C (131°F) for the FM30 or 72°C (162° F) for the FM100 and FM250,
ALC voltage begins to decrease, reducing the PA supply voltage to prevent a further
increase in temperature. By 60° C (140° F) for the FM30 and 75° C (167° F) for the
FM100 and FM250, the PA will be fully cut off. The heatsink fan (models FM100
and FM250 only) is proportionally controlled to hold the heatsink at 35
°
C (95° F).
Above this temperature, the fan runs at full speed.
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