Ericsson GF 768 Troubleshooting Manual page 47

4/00021-2/FEA 209 544/6 C
• If the VDSP voltage is too low, replace N701 (class A, fig. 9.6). The N701 circuit can only be replaced at 2/
ROA 119 3283/7 R2A boards. At the other boards the circuit is placed under the DSP shielding (E203). If
that's the case, send the phone to the next level.
• 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.
Measure the voltage at both sides of R601 and at D600 pin 70 (~5V, fig. 9.4 and 9.2, you follow the PHFI signal).
Measure the voltage at both sides of R605 and at D600 pin 67 (~5V, fig. 9.5 and 9.2, you follow the EXTAUDI
signal).
• If the voltage at only one side of R601 or R605 is too low, replace the corresponding resistor (fig. 9.4 and 9.5,
both of class A).
• If the voltage is too low at both sides of R601 or R605, check the VSIMPAD voltage at marked sides of R635
and R636 (~5V, fig. 9.4, R636 is mounted as in fig. 9.5 at 2/ROA 117 3748 boards).
• If the voltage isn't there, check the resistance from the marked side of R635 or R636 to N705 pin 3 (~0
ohms, fig. 9.5, 9.4, 9.2).
• If the resistance is too high there's a foil damage and the phone is to be discarded.
• If the resistance is correct, go to 7.3.
• If the VSIMPAD voltage is correct, measure the resistances of R635 and R636 (~22 kohms, fig. 9.4 or 9.5).
• If any of the resistances are incorrect, replace the corresponding resistor.
• Measure the resistance from X602 pad 5 to ground (>100 kohms, fig. 9.8). Make sure there's no dirt or oxide
between the components below the dome foil (the components in fig. 9.5).
• If the resistance is too low, wash carefully and measure again.
• If the resistance still is too low, remove R601 (class A, fig. 9.4) and measure again.
Fig. 9.7
Fig. 9.8
Troubleshooting guide
47