Nokia 6680 RM-36 Service Manual page 300

Nokia Customer Care
3.2.2.3.4 Replace Hinku (N7500)
3.2.2.4 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
3.2.2.4.1 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.
3.2.2.4.2 Replace Retu
3.2.2.4.3 Replace Hinku (N7500) or Vinku (N7501) or VCTCXO (G7501) or all three components
3.2.2.5 VCP1-voltage ok?
• GSM receiver has to be active before VCP1 voltage can be measured. Procedure is explained in
section "GSM RX chain activation for manual measurements".
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to C7507.
• VCP1 voltage should be about 4.75 V.
3.2.2.5.1 C7507 and C2222 working properly?
• Check that the components are in place and solder joints are ok
• Disconnect the power supply from the phone and use an ohmmeter to check that C507 and C2222
are not short-circuited.
3.2.2.5.2 Retu ok?
3.2.2.5.3 Hinku (N7500) ok?
3.2.2.6 VCTCXO frequency and output level correct?
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to C7529 (or C7582)
• The frequency of the VCTCXO should be quite exactly 38.4 MHz and level about 0.5 - 0.9 Vpp.
Example of the correct VCTCXO output signal is presented in figure
1.24
A-54
V)".
Copyright © 2005 Nokia. All rights reserved
Company Confidential
Appendix A: RF Troubleshooting
6.5.1 "VCTCXO Output (DC Offset