Ericsson GF 768 Troubleshooting Manual page 21

4/00021-2/FEA 209 544/6 C
4.3 The phone doesn't start when charger is inserted.
Open the phone and check for water damage, especially at the system connector. The phone is to be discarded if
the gold plating is damaged like in fig. 4.4.
It's usually dirty at the battery contact pads, which is shown in fig. 4.5. The pads are cleaned with a brush and
alcohol.
Measure the resistance from DCIO to VBATT (~390 ohms, fig. 4.5).
• If the resistance is too low, replace V450 (class A, fig. 4.3).
• If the resistance is too high, measure the resistance of R458 (class B, ~0.1 ohms, fig. 4.3) and R455 (class A,
~390 ohms, fig. 4.3).
• If the resistances are correct, measure the resistance from the marked side of R455 to DCIO (~0 ohms, fig.
4.3 and 4.5). If it is too high there's a foil damage and the phone is to be discarded.
Measure the resistance from GND (pad 10) to AGND (pad 4) at the system connector pads (~0 ohms, fig. 4.5). If
the resistance is too high there's a foil damage and the phone is to be discarded.
Give the board power and start it up by grounding N450 pad 6 (fig. 4.3).
• If the phone starts it can't be repaired at this level.
• If the phone doesn't start, replace V450 (class B, fig. 4.3). If that doesn't help, replace V704 (class A, fig. 4.2).
Fig. 4.4
Fig. 4.5
Troubleshooting guide
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