Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
48(78)
The fault is usually due to too low amplification in the power amplifier.
When the amplification is lower then normal, but still high enough for the phone to pass the
Power Level Calibration, the power amplifier is working at its maximum limit.
This can result in over tones in the shape of distortion.
The fault can also be due to noise at one of the feed voltages of the radio or an appearance of
unwanted frequencies (e.g. noise) in the output signal.
Open the phone and check for liquid damage.
Start the phone in the test program.
Start the transmitter of the phone in switched mode, choose highest power level, at channel 37
for EGSM900 or channel 699 for GSM1800.
Use an oscilloscope and measure the modulation signals (MODQN, MODQP, MODIN and
MODIP) from D600. Compare the signals with a reference-board.
The signals MODIP at R515 and MODQN at R512 (should look like Fig. 13.3) and the
frequency is 216 HZ.
Fig. 13.3
The signals MODIN at R514 and MODQP at R513 (should look like Fig. 13.4) and the
frequency is 216 Hz.