Tait TM8100 mobiles Service Manual page 172

Figure 7.2 Important components of the power-supply circuitry (top side),
including 9V regulator IC601
3V3 test point
Task 2 —
Check 3.3V Supply
172 Power Supply Fault Finding
Q600
If the inputs at pin 5 and pin 7 of IC602 in the SMPS circuitry are correct,
but the radio fails to power up, then the 3.3V DC supply needs to be
investigated.
1. First determine as follows if a fault on the digital board is affecting the
supply or preventing the radio from powering up: While keeping the
/ key depressed, measure the supply at the 3
ON OFF
the corner of the digital board (see
when there is no fault.
3V3 test point: 3.3 ± 0.1 V DC
If the voltage is correct, the digital board is faulty; replace the board
and go to "Final Tasks" on page
to Step 2.
LK8 (R786)
LK7 (R787)
3 test point near
V
Figure 7.2). The voltage is 3.3V
163. If the voltage is not correct, go
TM8100/TM8200 Service Manual
© Tait Electronics Limited November 2007