Ericsson GF 768 Troubleshooting Manual page 39

4/00021-2/FEA 209 544/6 C
next level.
• If VDIG is correct, measure the resistance of R706 (class A, ~4.7 ohms, fig. 7.4). Note that at the 2/ROA
117 3632/1 boards the resistor is placed as in "AREA B" in fig 7.4.
• If it's correct, measure the resistance from the marked side of R706 to the marked side of C600 (~0
ohms) and from the other side of R706 to N705 pin 2 (~0 ohms).
• If any of them are too high there's a foil damage and the phone is to be discarded.
• If the input voltage at N705 pin 2 is correct, measure the output voltage, VSIMPAD (~5V), at pin 3 of N705
(class A, fig. 7.4).
• If the voltage isn't correct, replace the circuit.
• If the voltage is correct there can be a foil damage between N705 pin 3 and R724 or between N705 pin 3
and V700 pin 1 (fig. 7.2 and 7.4). If there's a foil damage the phone is to be discarded.
7.4 VSIMPAD voltage is correct.
Open the phone and check for water damage. Clean the SIM pads, X600 (fig. 7.3), using alcohol and a brush.
Assemble the phone with a new SIM holder and try again.
If the fault remains, open the phone again.
Measure the resistance of R704 (class A, ~100 kohms, fig. 7.4).
Make sure there are no faulty solderings at D600 pins 72-75 and 64 (fig. 7.3).
Measure the resistance of R600 (class A, ~33 ohms), R627 (class A, ~0 ohms) and R628 (class A, ~100 ohms, all
in fig. 7.4). Note that at 2/ROA 117 3748/2 boards the R628 resistor is placed as in "AREA A" in fig. 7.4.
Measure the resistance from the marked side of R600 to X600 pad 2 (~0 ohms), from the marked side of R627 to
X600 pad 3 (~0 ohms) and from the marked side of R628 to X600 pad 7 (~0 ohms, all in fig. 7.3 and 7.4).
• If any of the resistances are too high there's a foil damage and the phone is to be discarded.
• If the resistances are correct, replace D600 (class B, fig. 7.3).
If the fault remains, send the phone to the next level.
Troubleshooting guide
39