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Troubleshooting
PAMS Technical Documentation
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Fault finding chart for GSM1800 transmitter
TXIQ signals look the same in EGSM and GSM1800.
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There is only one PLL synthesizer generating frequencies for both Rx and Tx in both bands (EGSM
and GSM1800). VCO frequency is divided by 2 or by 4 in HAGAR depending on which band is active.
Measure TX
power on "ANT"
Power > 27.5
dBm in 50 ohm
Measure TX
power on "Pout".
Power ~7 dBm in
500 ohm
Measure TX
power on "Pin".
Power ~-17 dBm
in 500 ohm
No
Measure TX
power unbal
T503. Power ~18
dBm in 500 ohm
With Osc check:
VTX = 2.7V +
discretes around
T503
Check POGO
pins, C593, L510
Yes
Measure TX power
on DCS_Tx. Power
~7 dBm in 500 ohm
With Osc on
RXTX switch
check: Vc1 =
2.7V, Vc2 = 0V
Yes
Check L515
(Coupler)
Check RXTX
switch
Yes
Check Hagar +
Serial bus
With Osc on PA
check:
Vpctrl GSM1800.
Vpctrl ~ 1.5Vpp
Yes
Check PA N502
Yes
No
No
Yes
No
No
No
Check R542,
R539, R543,
C566/Z504
Yes
No
With Osc check
TXC (see figure
?)
With Osc check
"Vpctrl" = "TXC"?
Yes
No
Check V503 +
discretes around
No
No