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Trouble Shooting Guide, Advanced
Change CF on the spectrum analyser to the calculated, by using the formula above.
Frequency for TXIF_GSM, the frequency of the transmitter usually ends up on ~890 MHz when
the synth does not lock on, that gives a frequency for TXIF_GSM at ~117 MHz and SPAN to 10
MHz.
Measure the amplitude for TXIF_GSM at N201 pin 13, 14 ~ -2 dBm.
If the amplitude is too low, it usually is due to N201.
If the amplitude is correct, follow the signal from N201 pin 13, 14 to N500 pin 10,11 through
R211, R212, C508, C509, C506 and C507.
If TXIF has got the right amplitude on N500, the fault can be due to N500, N570, N800, D600
or the components on the output N500 pin 12.
All values are approximate, measure the exact values for your equipment with an
approved phone.
For GSM 1800:
Start the transmitter in static mode on channel 699.
We propose the following settings on the spectrum analyser while measuring:
CF- 1747.6 MHz, SPAN- 200 MHz, RBW- 10kHz, VBW- 10 kHz and Sweep- 30ms.
Measure the amplitude and the frequency on the signals TXLOOP_DCS on N202 pin 1, 2 -11
dBm, the frequency should be 1747.6 MHz when the synth is locked on.
If the TXLOOP-signal is too low, the fault can be due to too large moderation in U204, C224 or
C225. The fault can also be due to N560 ~12 dBm, or its feed voltages.
If the level of the TXLOOP-signal is correct, check the amplitude on the signals LOINA and
LOINB on N202 pin 13, 14 ~ -10 dBm.
If the amplitudes on LOINA and LOINB are too low, the fault usually depends on U203 or the
components that belongs to it.
If the amplitudes on TXLOOP, LOINA and LOINB are correct, calculate the frequency on
TXIF_DCS by subtracting LOIN from TXIN.
On an approved phone it should be as follow:
TXIN 1747.6 MHz - LOIN 1669.6 MHz =TXIF_DCS 78 MHz
Change CF on the spectrum analyser to the calculated, by using the formula above.
Change Frequency for TXIF_DCS and SPAN to 10 MHz.
Measure the amplitude for TXIF_DCS on N202 pin 19, 20 ~ -20 dBm.
If the amplitude is too low, it is usually due to N202.
If the amplitude is correct, follow the signal from N202 pin 19, 20 to N500 pin 10,11 through
R576, R577, C506 and C507.
If TXIF has got the right amplitude on N500, the fault can be due to N500, N570, N800, D600
or the components on the output N500 pin 12.
All values are approximate, measure the exact values for your equipment with an
approved phone.
4/00021-3/FEA 209 544/18 B
18(121)
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