Fault Indicators - Crown FM30 User 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 motherboard.
A test lead connected to this point can be used for making voltage measurements 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 reference voltage used by the
metering circuit. 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 nu-
merically 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 pre-
set limit.
PA Temp—PA heatsink temperature has reached 50° C (122° F) for the FM30 and 80° C
(176° F) for the FM150 and FM300.
At about 55° C (131°F) for the FM30 or 82°C (180° F) for the FM150 and FM300, ALC volt-
age begins to decrease, reducing the PA supply voltage to prevent a further increase in
temperature. By 60° C (140° F) for the FM50 and 85° C (185° F) for the FM150 and FM300,
the PA will be fully cut off. The heatsink fan (models FM150°and FM300 only) is proportion-
ally controlled to hold the heatsink at 35 C (95° F). Above this temperature, the fan runs at
full speed.
3-8 FM30/FM150/FM300 User's Manual