High power—Fault finding and adjustments
238 NGT Transceiver System Technical Service Manual
Internal fault indicators
Internal faults of the power amplifier can be further diagnosed using the LED indicators
on the Control PCB inside the power amplifier. The meanings of the LED indicators are
provided in Table 16.
Table 16: Meaning of internal LED indicators on the Control PCB
Indicator Cause Action
LO GAIN Overall amplifier gain
too low
Check that the splitter and combiner are
working correctly
PSU FAULT Insufficient voltage at
the Power
Amplifier PCBs
Check that there is 70 V DC at DC input to
Power Supply PCB
Check that there is at least 33 V DC at DC
input to the Power Amplifier PCBs
Low bias supply Check that there is 5 V at 5V_BIAS pin of
the Power Amplifier PCBs
ALC
OVERVOLTAGE
Amplifier ALC output
not under control of
the NGT
Check the continuity of the ALC control
line between the amplifier and the NGT
COMBINER
UNBAL
2- or 4-way Combiner
PCBs giving unequal
power
Check the amplifier power supplies and
connections
Check each amplifier output individually
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