Glenayre Document Number: 9110.01002
GL-T8541 PA
09/10/99
CHECKOUT AND MAINTENANCE
t8541
p7.
fdk
Copyright © 1997 Glenayre
Page: 7-13
TABLE XX is a chart of symptoms and causes that should aid in the power amplifier
troubleshooting.
Table 7-3 PA Module Faults
Symptom
Problem Area
Item to Replace
No RF output, driver current at (or slightly below)
idle value, all PA currents at Idle value
Bad driver board Q1
Replace PA module
No RF output, low driver current, PA currents at idle
value
Bad driver board Q2
Replace PA module
Low or no RF output, low current for one or all PA
boards
Bad 1 to 3 splitter.
Replace PA module
Driver current normal, high currents on other PAs,
low current on this PA
Bad PA board transistor
Replace PA module
Driver current normal, high currents on other PAs,
zero current on this PA
Both PA transistors bad
Replace PA module
Low RF output, normal driver current, high current
on two of the PAs, low or high current on the
affected PA, possible discoloration of one combiner
board input
One input of 1 to 3 combiner
bad
Replace PA module
Low RF output, normal driver current, low or high
currents for all PAs, possible combiner board
discoloration
Combiner board RF path
problems
Replace PA module
RF output ok, all currents ok, excessive harmonic
content in output.
Combiner board low pass filter
defective
Replace PA module
Transmitter faults, fault indications show: RF output
power too high, PA board currents too high, AGC
voltage too high
Bad forward directional coupler
on combiner board, or bad AGC
circuit on metering board
Replace PA module, if
problem persists replace
metering board
** DSP VDT display shows no reflected power,
even if known mismatch present at PA RF output.
Bad reflected directional
coupler on combiner board, or
bad metering board reflected
power amplifier (U5A)
Replace PA module, if
problem persists replace
metering board
1. No RF output power; VDT display shows: zero
PA current, zero AGC, zero metering board supply
voltages; and LED1 on metering board not lite.
Fuse F5 blown
Replace F5
2. Symptom of problem 1 recurs
Fuse F5 Blown again
Replace metering board
3. Output power low or zero, zero current for one
amplifier board
Blown fuse (F1, F3, F6, or F8)
on metering board
Replace fuse
4. Refer to problem 3, above, same symptoms
Same fuse blown again
Replace the amplifier
board the fuse supplies
power to
5. Refer to problem 4, above, same symptom
Same fuse blown again
Replace metering board
