Ericsson GF 768 Troubleshooting Manual page 46

Troubleshooting guide
Wash the circuit board if needed using alcohol and a brush.
Assemble the phone and test it as in 9.1.
If the fault remains, open the phone. Give the board power and start it up by pressing the On/Off key without the
system cable connected.
Measure the VDSP (~3.2V) feed voltage. Fig. 9.6 shows the measuring point for VDSP. The figure shows three
possible placements of the VDSP regulator.
At the 2/ROA 119 3283/7 (R2A) and 2/ROA 117 3748 (all revisions) boards the regulator is placed outside the
DSP shielding and the VDSP voltage is easily measured.
At the 2/ROA 119 3283/7 (all R4 revisions) and 2/ROA 117 3632/1 (all revisions) boards the regulator is placed
under the DSP shielding (E203). You have to measure the VDSP voltage very carefully through one of the holes
in the shielding with a thin, preferably isolated, probe as in fig. 9.7.
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Fig. 9.5
Fig. 9.6
4/00021-2/FEA 209 544/6 C