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Trouble Shooting Guide, Advanced
For GSM 1800:
Give the board power, start the test program and connect the negative -4 V
again.
DC
Start the transmitter in static mode on channel 699.
Measure the voltage at N450 pin 4 VREG +1.7 V
.
DC
If VREG is too low, measure the signal POWLEV +0.9 V
at N450 pin 11.
DC
If the voltage POWLEV is too low, check the soldering at N800 pin 61.
If the soldering is correct, the fault is usually due to N800.
The fault can also be due to D600 or a short circuit in C833 or C853.
If POWLEV is correct the fault is due to a break in R413. It can be verified by measuring the
resistance between pin 17 and 18 at N450 0.1 ohm, or a short circuit of the control voltage
VREG caused by N401.
If VREG is too high, measure the signal TXLOOP_DCS at N202 pin1, 2 ~ -12 dBm.
If TXLOOP_DCS has got the right amplitude, check if there is a HF-signal at N401 pin 10 ~-6
dBm.
If the signal is missing it can depend on R408 or C441.
If the signal has got the right amplitude, the fault depends on N401.
If the amplitude on TXLOOP_DCS is too low, measure the HF- signal at N560 pin 1 ~-12 dBm.
If the signal on N560 has got the right amplitude, the fault probably depends on U204.
If the signal on N560 is missing, measure the feed voltage at N560 pin 6 +3.9 V
.
DC
If the feed voltage is correct, the fault probably depends on N560.
If the feed voltage is incorrect, the fault usually depends on L560, C560 short circuit, V560,
V561 or some of the following voltage are missing, SWDC the same voltage as VBATT,
VVCO +3.8 V
or TXON_DCS +3.7 V
. If TXON_DCS is missing, check D600, D102 and
DC
DC
D105.
If VREG is correct, measure the signal TXLOOP_DCS at N202 pin1, 2 ~ -12 dBm.
If TXLOOP_DCS has got the right amplitude, follow the HF-signal from N401pin18, 19,24 or
25 ~-5 dBm to Z205pin 5 ~-10dBm through V411, V205 and Z204.
If the signal on N401: 18,19,24 and 25 is too low, the fault probably depends on N401.
If the signal is too low at Z205pin 5, is it either attenuated too much somewhere along the path
or there is a fault in the antenna switch, V201 and V206 with the associated components.
If the amplitude on TXLOOP_DCS is too low, the fault can depend on U204, C224 or C225.
3.3
The transmitter does not lock
Give the board power and start the test program.
For GSM 900:
Start the transmitter in static mode on channel 62 and check the transmitters output power and
frequency.
We propose the following settings on the spectrum analyser while measuring:
CF- 902.4 MHz, SPAN- 200 MHz, RBW- 10 kHz, VBW- 10 kHz and Sweep- 30 ms.
Check the frequency of the transmitter 902.4 MHz.
4/00021-3/FEA 209 544/18 B
15(121)
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