Codan NGT 2010 RF Technical & Service Manual page 551

Fault finding the power amplifiers (3061/3062)
The power amplifiers have front panel LED indicators, which latch on in the event of a
fault; this latch clears when the fault is resolved and the NGT is switched off then on
again. The meanings of the LED indicators are provided in
Table 15: Meaning of LED indicators on the front panel of the power amplifier
Indicator
Over Temp No
High
VSWR
No power
bar graph
Fault
NOTE
NGT Transceiver System Technical Service Manual
Latching Likely cause
Heatsink temperature
over 70°C (158°F)
Yes Transmitter load
VSWR exceeds
approximately 3:1 on
a particular frequency
No Power amplifier
disabled
Power amplifier fault
detected
Yes Power supply fault
The type of fault indicated by the Fault LED can be individually
identified on separate LEDs on the Control PCB, which is located beneath
the top cover of the amplifier.
The power supply fault state may be due to external causes.
High power—Fault finding and adjustments
Table 15.
Action
Check that ambient room
temperature is below 45°C (113°F)
Check that airflow is unobstructed
and that power amplifier fans are
free to turn
Fault will clear when amplifier
returns to correct operating
temperature
Check antenna VSWR at full power
on the affected frequency
If the high VSWR fault occurs on all
frequencies, this indicates an internal
fault in the power amplifier
Check that power amplifier is
enabled at handset
Check that other amplifier fault
indicators are not lit
Check that power supply unit switch
is illuminated
The fault may also be due to:
• low gain of the amplifier
• ALC overvoltage
• combiner unbalance
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