AR 10036390, Operating And Service Manual

Page: 52 / 56

Model 800A3B
Rev D 36
4.2.1 General - Reading faults
The Model 800A3B incorporates relatively simple fault detection circuitry, which makes use of the digital
display panel to alert the user or technician which component(s) need service. Use of these indications can
usually expedite troubleshooting of the amplifier. Most faults can be immediately determined down to the
assembly level. If a reset is still indicated, turn off the RF power signal to the input of the amplifier, read and
record the fault indication displayed on the digital control panel for later reference. Then, use the RESET
function to see if the fault clears. If the fault clears, slowly bring the amplifier’s drive level back up and
ensure that recommended RF power levels are not exceeded. If the fault indication is no longer visible, the
fault may have been brought about by a temporary transient condition, component thermal condition or
excessive RF drive to the amplifier’s input. If the fault does not clear with the RF drive off, some other
problem exists in the amplifier.
When multiple faults have occurred they all may be read by scrolling. To scroll through multiple faults, press
the ALC key.
4.2.2 Power Supply Faults
Indication – PS3 or PS4
The main power supply has failed to produce DC voltage within the design range of the power supply. The
main power supplies are located on the bottom shelf of the amplifier.
4.2.3 Thermal Faults
Only RF module thermal faults are detected. See section 4.3.
4.2.4 ALC Fault
Indication – ALC
As stated previously, the power limit controls could not limit either the forward or reverse power to the preset
threshold. This can be a transient type of problem, if the fault can be cleared. If the fault cannot be cleared
with no RF input drive power, then there is a malfunction in the ALC board or associated circuit.
4.2.5 RF Module Faults
Any RF module fault will trigger amplifier shut down, including main power supplies. There are three
possible module faults – Over-current, Under-current and Thermal. Module faults are displayed as OC , UC or
TH , where OC =Over-Current, UC =Under-Current and TH =Thermal.
Thermal faults usually indicate ambient temperature is too high, there is inadequate air-flow through the
module heat sinks or there is a problem with the sensor in the module.
Over-current faults usually indicate there is a short circuit that would not clear on the module printed wiring
or component, or the module current limit is not adjusted correctly. Under-current faults usually indicate that
one of the output devices is defective and/or not drawing enough current.