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Trouble Shooting Guide, Advanced
We propose the following settings on the spectrum analyser while measuring:
CF- 902.4MHz, SPAN- 0 Hz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.
If the output power is correct, the fault was either the back cover or the antenna connection.
If the output power is too low, measure the control voltage POWLEV at N450 pin 11 using an
oscilloscope Fig. 17.1.
Fig. 17.1
If the control voltage is too low, the fault usually is due to N800. It can also be due to D600.
If the control voltage is correct, measure VREG at N450 pin 4 or N401 pin 3 ~3V, the same
frequency.
If VREG is too low, replace N450. If that does not solve the problem, replace N401.
If VREG is correct, measure the signal TXIN at N570 pin 1 ~13 dBm.
If the signal TX is correct at N570, check the output signal from N401 pin 18,19.24 or 25
~22dBm.
If the signal is too low, replace N401.
If it is correct, continue checking the signal against the antenna connection and compare to a
reference board.
If the signal TX is too low at N570 pin 1, measure the feed voltage at N570 pin 6 using an
oscilloscope, ~3.8 V, 215 Hz.
If the feed voltage is correct, replace 570. If that does not solve the problem, replace N401.
If the feed voltage is incorrect, the fault usually is due to anyone of V570, V571 or V572.
For GSM 1800:
Start the transmitter in switch mode at channel 699 with DAC 7 value at "FF".
Check if there is enough output power,28- 32 dBm, at the antenna connector, use the spectrum
analyser.
We propose the following settings on the spectrum analyser while measuring:
CF- 1747.6 MHz, SPAN- 0 Hz, RBW- 300 kHz, VBW- 100 kHz and Sweep- 0.8 ms.
If the output power is correct, the fault was either the back cover or the antenna connection.
4/00021-3/FEA 209 544/18 B
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