Ericsson GF 768 Troubleshooting Manual page 11

4/00021-2/FEA 209 544/6 C
• If the voltage is missing at one or more of the resistors, measure the resistance from marked side of C600 to
the marked side of the resistor (~0 ohms). If the resistance is too high there's a foil damage and the phone is to
be discarded.
Measure the voltage at the opposite side of the resistance (~3.2V).
• If the voltage is too low at one or more of the resistors, check the resistance of the corresponding resistor (all
of them 100 kohms and class A). If the resistances are correct, check the solderings at D600 pads 120, 122-
128 and 1. If the solderings are correct, replace D600 (class B, fig. 2.1).
If the voltages are correct at both sides of R630-R634 but the keyboard doesn't work, check the solderings at
D600 pads 120, 122-128 and 1. If the solderings are correct, replace D600 (class B, fig. 2.1). If it doesn't help,
remove the dome foil again. Check for voltage (~3.2V) at marked sides of the key pads in the row of the non-func-
tional keys (fig. 2.6). Observe that there is VBATT voltage (~4.8V) at the marked side of the "No"-key. If the
VBATT voltage at the "No" key is missing there's a foil damage and the phone is to be discarded.
Fig. 2.5
Troubleshooting guide
11