5.15 Fgu Failure - Motorola APX 1000 Detailed Service Manual

Troubleshooting Charts: FGU Failure

5.15 FGU Failure

FGU Failure
Tx Injection /Rx
LO low power?
No
Yes
Correct Tx/Rx
No fault found.
frequency?
No
VCO Failure
Yes
Remove VCO shield
(SH11).
Yes
Tx?
No
Yes
No Check power at
input of U738 pin 1
Yes
Is power
>-20dBm?
No
No
1.5Vdc at L739?
Yes
Yes
< 0.5Vdc at pin 3
of Q745?
No
Yes
Is power at C740
>-20dBm?
No Check 1.5Vdc
1.5Vdc at L759?
supply.
Yes
Yes < 1.5Vdc at pin 2
< 0.5Vdc at pin3
of Q767? of Q785?
No
Check logic in PA
section.
Check parts around
Is power at C817 Yes
Q774. If OK, replace
>-20dBm?
Q774.
No
2.5Vdc at U738 No
Remove FGU shield
logic pin? (SH5).
2.5Vdc at U738 No
logic pin?
Yes
Check parts around
U738. If OK, replace
U738.
Check 1.5Vdc
supply.
Check parts around
Q745. If OK, replace
Q745.
Check parts around
Q756. If OK, replace
Q756.
No
< 0.5Vdc at pin 6
of Q785?
Yes
No
Check parts around
Q785. If OK, replace
Q785.
Replace U702.
5-45
Check parts around
Yes
Q767. If OK, replace
Q767.