Motorola 880 Service Manual page 58

Dual Band 880/890 (DCS/GSM)
#11 NPU Repair Procedure
Radio is resetting.
If the radio executes external device communication and then powers itself down
very shortly after attempting power up, it is resetting. A reset can be caused by a
fault on either U703, U500, or U701.
• Check that U703, U500, or U701 are not physically damaged, have no dry joints,
and are positioned correctly. If none of the mentioned problems are apparent.
• Ensure that the watchdog pull up pads R904 are shorted together, and monitor
U703, U500, or U701 to see if any become warmer than the other components.
Should any of the mentioned components become warmer— replace it.
If the above information does not pin point a specific component, replace the
following components in the order shown:
1st - Replace U500
2nd - Replace U703
• Check the PCB after each component change, to verify whether or not the fault has
been eliminated.
If after replacing the two components the fault is still apparent return PCB to a
Motorola Hi Tech Center.
50 68P09403A50 12/9/97