Ericsson T28S Troubleshooting Manual page 6

Trouble Shooting Guide, Standard
Check the solder joints at N200, Z200 and Z201.
Measure the resistance at R220, R221, R222 and R223, (all 0 Ohm).
Replace if incorrect.
Measure the resistance over L200 and L201, (0 Ohm).
Replace if incorrect.
Check that C312 is correctly soldered.
Try to get SERV again with the settings mentioned above.
If the phone gets SERV, go to section 2.3.
If the phone still not get SERV, the fault probably is within the LO part or there are too large
losses in the signal path. It is also possible that the feed voltages are incorrect.
Open the phone.
Power up the board and start it by pressing the On/Off key.
Measure the VRAD voltage at C501, at the pin close to N700 (3.80 V).
If the voltage is incorrect, send the unit on according to the local company directives.
Measure the V380B voltage at C500, at the pin close to C421/C424 (3.80 V).
If the voltage is incorrect, send the unit on according to the local company directives.
Measure the VVCO voltage at pin 5 of N502 (3.80 V).
If the voltage is correct, measure the resistance over R362 (18 kohms) and R363 (100 ohms).
Replace if incorrect.
If both the resistances are correct, go to section 2.2.1.
If the voltage at pin 5 of N502 is incorrect, measure the voltage at pin 1 of N502. It shall be
more than 4.10 V.
If the voltage is correct, replace N502.
If the voltage at pin 1 of N502 is incorrect measure the resistance over R503 (0 ohm), L500 (0
ohm), C503 (> 100 kohms) and C502 (> 100 kohms).
Replace if incorrect.
If all the resistances are correct and the voltage at pin 1 of N502 is 3.70 V replace V500.
If the fault remains, send the unit on according to the local the company directives.
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