Ericsson GH 688 - Page 20

GH688,GA628, Standard Electrical Repairs
4/00021-2/FEA 209 544/1.G 20 (112)
3.4.4 The phone works as long as the On/Off-key is
pressed.
GH688
Open the phone and check for liquid damages.
Make sure the system connector pads aren’t burnt.
Insert the board in the fixture. Start it up and keep it going by keeping DCIO high.
Measure the voltage at C692 (~3.1V, fig. 3.2).
• If there is voltage, check the soldering at D600 pin 119.
• If there isn’t voltage, measure the resistance of C692 (class A, >200 kohms).
* If the resistance is correct, measure the input voltage at N706 pin 2
(VBATT) and the output voltage at N706 pin 3 (~3.5V). Make sure that the
regulator has ground at N706 pin 1. There is a foil damage if the ground or
VBATT is missing at N706 and the phone should be discarded.
* If the input voltage and the ground are correct, replace N706 (class A).
* If the output voltage is correct, measure the voltage at the positive side
of the backup capacitor (C720, class A, ~3.1V).
* If there is no voltage, replace V711 (class A).
* If there is voltage, check the resistance from the positive side of C720
(fig. 3.5) to C692 (~0 ohms).
* If the resistance is too high there is a foil damage and the phone
should be discarded.
GA 628
Open the phone and check for liquid damage.
Make sure that the system connector pads aren’t burnt.
Insert the board in the fixture. Start it up and keep it going by keeping DCIO high.
Measure the voltage at C692 (~3.1V, fig. 3.2, the figure shows a GH 688 board but
the capacitor is placed at the same location).
• If there is voltage, check the soldering at D600 pad 119.
• If there is no voltage, measure the resistance of C692 (class A, >200 kohms).
* If the resistance is correct, measure VDIG.
* If the voltage at VDIG is incorrect, see 3.4.1, 3.4.2 or 3.4.3.
* If VDIG is correct, check the resistance from N702 pin5 (fig. 3.2) to
C692 (~0 ohms).