GH688,GA628, Standard Electrical Repairs
4/00021-2/FEA 209 544/1.G 10 (112)
Fig. 2.5
Measure the DC voltage at pin 1 and 2 of G350. The voltage at pin 1 (control volt-
age) should always vary between ~0.8V - ~2.8V (usually starts at ~1.7V). The volt-
age at pin 2 (feed voltage) also varies but usually starts at ~3.3V (fig. 2.3).
• If the feed voltage is incorrect (usually no voltage at all), check the soldering at
D600 pin 102 (fig. 2.1).
* If the soldering isn’t faulty, send the phone to the next level.
• If the control voltage is incorrect (usually ~0V or ~3.6V), check if C370 (class
B) and R357 (class B) are mounted (both of them in fig. 2.3).
* If that is the case, replace N350 (class B, fig. 2.3).
* If that doesn’t help, replace G350 (class B, fig. 2.3).
Measure the resistance of C540, C541, C542, C543, C544 and C545 (all of them
class B, >200 kohms, fig. 2.3)
Check the solderings at C826 (fig. 2.4), Z201, Z500, Z501 and Z502 (fig. 2.3).
If the problem isn’t solved, send the phone to the next level.
2.2 Connect a call at powerlevel 5 using an
instrument with –68.5dBm signal strength.
• If it works, proceed to section 2.3.
• If it doesn’t work, open the phone and check for liquid damage. Make sure the
ground foil around the antenna connector isn’t dirty.
Check the antenna connector, X401 (class A, fig. 2.2), and make sure that it isn’t
damaged or dirty (glue, varnish, oxide…) and that the solderings aren’t faulty.
Replace the back cover and try again.
• If it doesn’t work it most likely means that the problem is Tx-related.
Check if C300, C403, L300, V300, V301 or V302 (all class A, fig. 2.6) are burnt.
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