…..The specific procedure is as follows: First connect the mobile phone to the test fixture with an USB data cable. Activate the Phone Tools program and select Non-signaling interface. Then select the channel and power level to be tested, and click Tx Start. The mobile phone is in the transmitting state. Adjust the spectrum analyzer to the relevant channel. Check the output of the RF and confirm whether the output power is normal. If it is normal, it indicates that the RF link is not faulty. In that case, check whether the X101 crystal and the CPU (U101) have a soldering problem or not. Re-soldering or replacement can solve the problem. Calibration failure of GSM and DCS receiving circuit result is usually from faults of the GSM and DCS receiving links. Check whether U101, U102 and U104 (GSM SAW filter) as well as U105 (DCS SAW filter) have bad soldering. Usually the dry soldering problem of the U104 or U105 causes the excessive attenuation of the receiving RF signals. Re-soldering can solve the problem. The calibration failure of GSM and DCS transmitting power results is usually from the dry soldering of U102 and U103. The dry soldering leads to the cut of the transmitting channel or the locking failure of the transmitting RF. Check them and re-solder the places of dry soldering.
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