Motorola APX 1000 Detailed Service Manual page 805

Troubleshooting Charts: PA Failure
PA Failure – Page 4 (ALC)
5
Remove SH15 and measure
PA control voltage at
U901 for VHF,
U1601 for UHF1/UHF2 and
U1001 for 700/800 MHz
pin 4
VC_OFFSET low,
remove SH6
Yes
Is U901/U1601/U1001/
Pin 1 about 2.5V?
No
Yes
Is U1202 Pin 5 about
2.3+/-0.2V?
No
Is U1251 Pin 1 Yes
about 2.3+/-0.2V?
No
Is U1282 Pin 6 Yes
about 2.3+/-0.2V?
No
Is U1269 Pin 3 Yes
about 2.3+/-0.2V?
No
Yes
Is U1253 Pin 1
about 2.3+/-0.2V?
No
Is U1201 Pin 1
Yes
about 5V at DAC 4095?
No
Replace U1201
Replace U901/U1601/U1001
Replace U1202
Replace U1251
Replace U1282
Is U1269 Pin 1
ANA_CTRL_ISET
about 5V?
Yes
MAKO Ramp is working fine
Replace U1253
Replace R1244
U1269 is a smaller picker. If Pin 1 measured voltage was
lower than Pin 3, Pin 1 voltage will be picked as V-control
and caused no or low V_control to bias PA, resulting no
or low TX power
5-49