Ericsson PF 768 Troubleshooting Instructions page 35

PF768, Standard Electrical Repairs
Fig. 6.4
• If the input voltage is too low or missing, check the VDIG (~3.2V) feed voltage
at C600 (fig. 6.4).
* If the VDIG voltage is too low, measure the resistance from it to ground.
* If the resistance is more than 500 ohms, replace N702 (class A, fig. 6.4).
* If it's less, send the phone to the next level.
* If the VDIG voltage is correct, measure the resistance of R706 (class A,
~4.7 ohms, fig. 6.4).
* If the resistance is correct, check the resistance from the marked side of
R706 to the marked side of C600 (~0 ohms) and from the unmarked side
of R706 to pin 2 of N705 (~0 ohms).
* If any of the resistances are too high there's a foil damage and the
phone is to be discarded.
• If the input voltage is correct, measure the output voltage (VSIMPAD, ~5V) at
N705 pin 3 (class A, fig. 6.4).
* If it's incorrect, replace N705.
* If the output voltage is correct there can be a foil damage somewhere
between N705 pin 3 and R724 or between N705 pin 3 and V700 pin 2 (fig.
6.2 and 6.4). If there's a foil damaged the phone is to be discarded.
6.4 VSIMPAD voltage is correct.
Open the phone and check for liquid damages.
Clean the SIM pads using alcohol and a brush.
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