Motorola 880 Service Manual page 54

Dual Band 880/890 (DCS/GSM)
#1 NPU Repair Procedure
No +6.5V dc battery supply voltage present at pin 40 of U900.
• Check the PCB battery contact assembly for dry joints to the PCB, or broken
contacts. Resolder any dry joints, or replace the battery contact assembly if any of
the contacts are broken.
• Check the PCB external connector J600 socket on or around pin 2 for dry joints to
the PCB or broken contacts.
• Check for +6.5Vdc at pin 40, U900 both with battery and external power. If no B+
with battery check Q906. If no B+ with external power, check CR903.
If replacing the above components does not eliminate the fault, return the PCB to a
Motorola Hi Tech Center.
#2 NPU Repair Procedure
No regulated +2.75V dc voltage present at U900 pins 22 and 28.
The components that will most likely affect the regulated +2.75V supply are the B+
supply, and U900. Check that B+ related components are not physically damaged,
have no dry joints, and are positioned correctly.
If none of the above mentioned problems are apparent, you can either take measure-
ments on the defective PCB to decipher which component(s) you feel should be
replaced, or replace the following components in the order shown:
1st - Replace L902, L903, C916
2nd - Replace U900
• Check the PCB after each component change to verify fault elimination.
If replacing the above components does not eliminate the fault, return the PCB to a
Motorola Hi Tech Center.
46 68P09403A50 12/9/97