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Trouble Shooting Guide, Advanced
The mixers input signal usually is:
947.4 MHz:
~ -56 dBm at N201 pin 5, 6. Follow the signal from the antenna-connection -50 dBm, to the
mixer.
The input signal to the filter Z201 pin 2 should be ~ -51 dBm.
The signal coming out of the filter is balanced Z201 pin 4,6.
The filter attenuates the signal 5-7 dBm in the pass band.
If the input signal to the filter is to low, it usually is Z205, L223 or Z201 that is faulty.
If the filter attenuates the signal too much, it usually is Z201 that is faulty.
772.4 MHz:
~ -7 dBm at N201 pin 17, 18 and ~ -0 dBm at N303 pin 1.
Follow the signal from LO-VCO through the balun U201, where the signal is balanced, to the
mixer.
If the mixers amplifying is to low it is usually the N201 that is faulty.
The 175 MHz-signal is mixed down to 6 MHz in N500.
Measure the signal 6 MHz on Z500 pin 6, 0 dBm, Z500 pin 1, -7 dBm, N500 pin 44, -7 dBm,
N500 pin 40, -5 dBm.
If the signal attenuates too much over Z500 is it probably the filter that is faulty.
If the signal attenuates too much from N500 pin 44 to N500 pin 40 is it probably L505 or C521
alt. C505 or C520 that is faulty.
Check the DC voltage at C530 - C535 +2.1 V
.
DC
If any of them is lower then replace that capacitor.
If the attenuates in the signal path are correct, the fault can depend on noise on some of the feed
voltage or noise on the control voltage to N303.
Noise on the control voltage is mainly due to N301or C318.
The fault can also be due to N800, D600 or N500.
NOTE! If you replace N800 you must perform a "Voltage and current calibration".
All values are approximate, measure the exact values for your equipment on an operating
phone.
19.4 GSM 1800
Open the phone and check for liquid damages.
No further action should be taken for a liquid damaged telephone.
Attach the board to the fixture and start the test program.
Set Radio in RX Static mode on channel 699 Fig.19.3.
Static RX is active after you have clicked on the Apply-button.
4/00021-3/FEA 209 544/18 B
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