Ericsson GF 768 Troubleshooting Manual page 49

4/00021-2/FEA 209 544/6 C
circuit board (fig. 9.4).
Check the solderings of N800 (fig. 9.2).
Give the board power and start it up by pressing the On/Off key without the system cable connected.
Measure the voltage at the marked side of R825 (~3.1V, fig. 9.4).
• If there isn't any voltage or if it is incorrect, check the VANA voltage at the marked side of R830 (fig. 9.4).
• If the VANA voltage is incorrect, go to chapter 6.
• If VANA is correct, check the resistances of R830 (~470 ohms), R825 (3.3 kohms) and C835 (>1 kohms,
all of class A and in fig. 9.4).
• If there's correct voltage at R825, check the resistance of C810 (>10 kohms), C812 (>100 kohms), R802 (~3.9
kohms) and R805 (~15 kohms, all of class A and in fig. 9.3). At 2/ROA 117 3748 boards the R802 is a 10
kohms resistor and the R805 is a 5.6 kohms resistor.
If the fault remains, send the phone to the next level.
9.6 Handsfree speaker out of order.
The fault occurs when there's an interrupt in the audio path from the N800 to the handsfree speaker (connected
through the system connector). The audio path is shown in fig. 9.10.
Open the phone and check for water damages, especially around the system connector pads (X602, fig. 9.8) 1, 2
and 4.
Measure the resistance of C850 and C851 (both >100 kohms, of class A and in fig. 9.4).
Make sure all the components in fig. 9.10 (R803, R804 and C813) are mounted at the circuit board (fig. 9.4).
Check the solderings of N800 (fig. 9.2).
Measure the resistances of R803 (~100 ohms), R804 (~100 kohms) and C813 (>100 kohms, all of class A and in
fig. 9.4).
Measure the resistance from the marked side of C813 to pad 1 of X602 (~0 ohms, fig. 9.3 and 9.8).
• If the resistance is too high there's a foil damage and the phone is to be discarded.
If the fault remains, send the phone to the next level.
9.7 Both the microphone and the speaker of the handsfree out of order.
Open the phone and check for water damages, especially in the marked area in fig. 9.8 above the system connector
pads.
Wash the marked area using alcohol and a brush.
Measure the resistance from X602 pad 3 to the unmarked side of R635 (~0 ohms, fig. 9.8 and 9.5).
Measure the resistance from X602 pad 2 to the unmarked side of R636 (~0 ohms, fig. 9.8 and 9.5/9.4).
• If any of the resistances are incorrect there's a foil damage and the phone is to be discarded.
Measure the resistances of R601 and R605 (table 9.1, class A, fig. 9.4 and 9.5).
If all the resistances are correct, check the solderings of N800 and D600 (fig. 9.2).
If the fault remains, send the phone to the next level.
Fig. 9.10
Troubleshooting guide
49