Ericsson PF 768 Troubleshooting Instructions page 28

PF768, Standard Electrical Repairs
4.7 Both the microphone and the speaker of
the handsfree out of order.
Open the phone and check for liquid damages, especially at the components in fig.
4.5.
Wash the above mentioned components using alcohol and a brush.
Measure the resistance from X602 pad 3 to the unmarked side of R635 (~0 ohms,
fig. 4.6 and 4.5).
Measure the resistance from X602 pad 2 to the unmarked side of R636 (~0 ohms,
fig. 4.6 and 4.4).
• If any of the resistances are incorrect there's a foil damage and the phone is to be
discarded.
Measure the resistances of R601 and R605 (~1 kohms, class A, fig. 4.3 and 4.5).
If all the resistances are correct, check the solderings of N800 and D600 (fig. 4.3
and 4.2).
If the fault remains, send the phone to the next level.
4.8 The phone sounds strange (the sound is
distorted, scrambled, full of static or
"chopped").
Open the phone and check for liquid damages.
Give the board power and start it up by pressing the On/Off key.
Measure the VDSP feed voltage (~3.2V, fig. 4.3).
• If the VDSP voltage is too low, replace N701 (class A, fig. 4.3).
* If the VDSP voltage still is too low after replacing the N701 circuit there is
probably a short circuit in one of the components fed by the VDSP voltage
regulator. If that's the case, send the phone to the next level.
• If the voltage is correct, check the solderings of N800 and D600 (fig. 4.3 and
4.2).
If the fault remains, send the phone to the next level.
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