Common faults on the 6200,8200,8400

-The phone gets warm / intermittant power up. 
 Chip XC94Ann (U430) IF AMP has blown. (RF path) 

-SIM card sticks, when removed card shows sigh of heat dammage
 U430 you can fry an egg on that sod.

-Wont log onto network
 Hey...its that damm U430 again

-Loggs onto network but wont make calls
 Insulating peice of foam rubber 10 mm long & 4 mm thick ,near the antena
 is actually conductive, shorting the output from the PA stage
 (MOSFETS) - Bad design.

-7500 powers down when you make a call.

 The screw that is used to hold the phone together, has clipped a
 capicitor (C359) which is connected to the PA control ic (U305)
 This controls the gain of the PA stage (Power Amp). The cap is part of
 the feedback loop to regulate output power. No cap, PA goes overboard
 on the O/P power, this is detected by the PA control ic (U305) and it
 sends a signal called SAT_DECT to the modem (U500). this then sends a
 powed down command to U701 and the radio switches itself off.

 On power and placed in test mode 7100# reports 03 or 04 indicating
 that the Modem (U500) is faulty, it not faulty.

The 5200 and 7200 often suffer from dry joints on the firmware PROM's