Motorola APX 7000 Detailed Service Manual page 158

5-54
PA Failure – Page 6 (7/800 ALC)
PA_OFFSET low,
check U1125 pin 1
for approx. 1V, else
replace U1133
Measure TP120
TP120 1.8V?
Yes
Replace U1139 or
associated logic
Replace U1129, U1130
Remove SH5 & measure
PA control voltage at U1001 pin 4
Measure voltage at U1145 pin 1
No
U1145 pin 1
VC_OFFSET low,
remove SH13
2.2V +/- 0.3V?
Yes
U1133 pin 6
about 5V?
No
Yes
U1133 pin 3 4.5V
+/- 0.5?
No
Yes
No
Remove SH9 and
R1181 5V?
measure U1142 pin4
No
Check P101 or VOCON
signal DIG_CTRL_IO49
Measure voltage divider
at power tuning DAC,
Power tuning is low, else
No
replace U1125, else U1137,
U1138.
Measure TP101 voltage
Yes
Remove SH11 & measure
output pin 4 of U1130
Yes
U1130 pin 4 U1127 pin 4
approximately approximately
1.15V?
1.15v?
No
Replace U1127,
Yes
else U1126
U1101 Pin 1
< 1.3V?
No
Transmitter PA overcurrent condition,
else check U1101, R1103.
6
Yes
Replace U1001
TX in Current control mode?
Yes
U1131, pin 4
is 5V?
No
Replace U1132
Yes
U1142 pin 4
Measure thermal cutback circuit
1.15V +/- 0.01V?
output at U1113, U1114, and U1121
No
top of R1121
R1121 around
1.15V +/- 0.015?
Yes
ANA_CTRL_ISET low. Check R1160
No
for wrong value, else check connector
TP101 1.5V?
P101, or MAKO IC on Vocon
Yes
Replace U1142
No
Troubleshooting Charts: PA Failure
TX is in current control mode, else PA is
saturated. Check SAT Reference tuning
per 12M to ensure tuning is not low.
Pin 4 of U1113,
Yes
Replace log amp, U1105,
U1114, & U1121
else U1112, else check
at 0V (logic low)?
R1106 for 17 +/- 1 Ohm
No
Check temp sensor
U1103, else U1148