Motorola StarTAC 160 Service Manual page 45

StarTAC 160 (GSM)
#5 NPU Repair Procedure
The +2.75V dc supply is missing at one or more of pins 33, 34, 42 and 124 of U701.
Pins 33, 34, 42, and 124 are each fed via pull up resistors R702, R706, R701, and R702
respectively.
• Check that all the pull up resistors are present, not physically damaged and that
there are no dry joints on either the resistors or U701.
If after replacing the above components the fault is not eliminated, return the PCB to
a Motorola Hi Tech Center.
#6 NPU Repair Procedure
The reset line at pin 30 of U900 does not go high to +2.75V dc.
• Check that U900 is not physically damaged, has no dry joints, and is positioned
correctly. If none of the mentioned problems are apparent replace U900.
If replacing U900 the fault is still apparent return PCB to a Motorola Hi Tech Center.
#7 NPU Repair Procedure
The watchdog line at pin 31 of U900 does not go high to +2.75V dc.
The watchdog line is pulled high by U701 when it receives and executes the initial
blocks of software from the PROM's U702 and U705. If there is a problem with either
U701, U702, U704, or U705 the watchdog will not be pulled high. This will cause
U900 to power down the +2.75V regulator's and halt the power up process.
• Check the CE lines at U701, U804, U702, and U705 for activity.
• If there is no activity, proceed to NPU repair procedure 8.
• If above activity is present, check for activity at pin 42 and 43 of U704.
• If there is no activity, proceed to NPU repair procedure 9.
• If above activity is present, check the OE+ line at pin 1 of U705 for activity.
• If there is no activity, proceed to NPU repair procedure 10.
If the above procedures don't eliminate the fault, return the PCB to a Motorola Hi
Tech Center.
38 Issue 1.0 2/6/98