Ericsson GF 768 Troubleshooting Manual page 44

Troubleshooting guide
If the fault remains, send the phone to the next level.
9.3 Microphone out of order.
Open the phone and check for water damages.
Wash the system and microphone connector pads if needed.
Most of the microphone faults are mechanical.
Makes sure that R816 (class A), C816 (class A) and C820 (class A) are mounted at the circuit board (fig. 9.3). The
components easily fall off when removing the system connector.
Make sure the sound channel gasket is properly mounted and free from dust.
Replace the system connector and microphone with a pair you know works. Test the phone again.
• If the fault remains, measure the resistance of C850 and C851 (both >100 kohms, class A, fig. 9.4). Measure
the resistance of R816 (~470 ohms, fig. 9.3, class A), R817 (~1 kohms, class A, fig. 9.4) and R819 (~1 kohms,
class A, fig. 9.4). Check the solderings of N800 (fig. 9.2).
• If the fault really is electrical and the above mentioned components aren't faulty, replace C818 and C819
(fig. 9.4, class A).
If the fault remains, send the phone to the next level.
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Fig. 9.2
Fig. 9.3
4/00021-2/FEA 209 544/6 C