Nokia 6680 RM-36 Service Manual page 301

Appendix A: RF Troubleshooting
3.2.2.6.1 VXO-voltage ok? (=Vdig).
• Measurement can be done with an oscilloscope and a probe
• Connect the probe to C7560 (or C7526, C7513)
• VXO-voltage should be about 2.5 V
3.2.2.6.1.1 C7560, C7513, C7526 and C2214 ok?
• Check that components are in place and solder joints are ok
• Disconnect the power supply from the phone and use an ohmmeter to find out if the VXO-line is
short-circuited to the ground. If short-circuit is found replace C7560, C7513, C7526 and C2214. If
replacing does not help then go to the next steps.
3.2.2.6.1.2 Replace Retu
3.2.2.6.1.3 Replace Hinku (N7500) or Vinku (N7501) or VCTCXO (G7501) or all three components
3.2.2.6.2 BB AFC-voltage ok?
Measurement can be done with an oscilloscope and a probe
•
• Connect the probe to R7509 (or C7533)
• AFC-voltage may vary between 0.1 - 2.3 V. Typical value is 1.2 V. Phoenix "RF Controls" tool can be
used to change the AFC value. Voltage level should be about 0.1 V with AFC value -1024 and about
2.3 V with AFC value 1023.
3.2.2.6.2.1 Low pass filter components R7509 and C7533 ok?
Check that components are in place and solder joints are ok
•
• Disconnect the power supply from the phone and check R7509 resistance value with an
ohmmeter.
• Use an ohmmeter to find out also if the AFC-line is short-circuited to the ground. If short-circuit is
found replace C7533. If this does not help then go to the next steps.
3.2.2.6.2.2 VCTCXO ok?
• Remove R7509. If AFC-voltage is correct after removing then replace faulty VCTCXO G7501 and
solder R7509 (new component) back to the PWB
3.2.2.6.2.3 Replace Retu
3.2.2.6.3 Replace VCTCXO G7501
3.2.2.7 Is there RF power in the RX VCO output at all?
• GSM receiver has to be active before RX VCO's output frequency and output level can be measured.
Procedure is explained in section "GSM RX chain activation for manual measurements".
• Measurements can be done with a spectrum analyser and an RF probe. Spectrum analyser centre
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