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Customer Care Europe, Middle East & Africa
SCCE Training Group
If 897.6 MHz TX-spectrum at L514 is ok, check same signal at C605. Amplitude normaly is around –3 dBm.
If no spectrum is measurable or amplitude is too low, check solderings of balun T504 and filter Z503.
Check if attenuation of filter Z503 is ? 2.7 dBm, also check if TX-buffer V601 works:
Voltage at collector of V601 is 2.4 Vpp while voltage at base is 0.8 Vpp. Change V601/602 if necessary.
If 897.6 MHz at C605 is ok, check TX-spectrum at L515 pin 1, +5 dBm up to +33 dBm.
If amplitude of spectrum at L515 pin 1 is not measurable or too low, check signals for power amplifier N502:
Check VBATT 4 VDC at C570/572.
-
Check Vapc at C565, which varies between 1.2 Vpp and 1.7 Vpp depending on TX-power level:
-
Figure 12-12
If these values are ok but amplitude of TX-spectrum at L515 pin 1 is too low, change the power amplifier N502.
If also the power amplifier works well, check TX-spectrum at J502 (antenna pad): amplitude varies depending on choosen
TX-power level between +5 dBm and +33 dBm.
If amplitude is too low, check mechanical appearance and solderings of coupler L515.
But it is more likely that the diplexer Z502 is responsible for this fault:
Check TXVGSM 2.5 Vpp at both sides of L509, which sets the diplexer into TX-mode.
Especially check the ceramic bottom plate of the diplexer if broken. This often happens if phone has been
.
dropped
No or too low TX power GSM 1800
Use WinTesla to set phone in following mode:
Initialize/ Product/ Band/ PCN/ Testing/ RF Controls/ active unit TX Ch.700
To find a fault in GSM 1800 TX mode you can proceed almost the same way as described for GSM 900:
Check 26 MHz reference oscillator at C546, -10 dBm, frequency deviation < 100 Hz
Check TXI/Q signals at R541/548. If not ok, check signals for COBBA N100 (VBB 2.8 VDC at C119, VCOBBA 2.8 VDC at C116/117,
VREF 1.5 VDC at C109 and COBBACLK at J317). Change COBBA if necessary.
Check 1747.8 MHz at L512. If not ok, check signals for HAGAR N500 (VTCXO 2.7 VDC at C506/518, VCHP 4.7 VDC at C505,
VSYNTE 2.7 VDC at C501/502/504, VRXRF 2.8 VDC at C500/503, VREF_2 1.35 VDC at C535/536, RXREF 1.2 VDC at C529,
furthermore SCLK/SENA at R301, SDATA at R300, TXC at C542, TXP at J503, HAGARRESET at C540 and signal of
SHF- oscillator at T502 = 3495.6 MHz).
Check 1747.8 MHz at C566. If not ok, check/change T503.
Check 1747.8 MHz at L515 pin 3. If not ok, check/change R542/N502
Check 1747.8 MHz at J502. If not ok, check L515 in & out, check also signal at Z502 in & out and TXVDCS 2.5 Vpp squarewave
at L508 ( sets Z502 to TX-mode ).
© NMP 2002
CONFIDENTIAL
NHM—2/5/6
3410
Date 20.11.2002
Checked by:
Customer Care E&A
37 (44)
Repairhints
Version 4.0 Approved
Approved by:
SCCE Training Group
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