Nokia RM-57 Service Manual page 243

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Disconnect the power supply from the phone and check R7503 resistance value with an
•
ohmmeter
3.1.1.1.3.1.3.2 Capacitors C7518, C7520 and C7570 working correctly?
• Check that components are in place and solder joints are ok
• Disconnect the power supply from the phone and use an ohmmeter to check that capacitors
are not short-circuited. If short-circuit is found replace capacitors mentioned above. If this
does not help go to the next step.
3.1.1.1.3.1.3.3 Replace Vinku (N7501) or Hinku (N7500) or both
3.1.1.1.3.1.4 Replace Vinku (N7501)
3.1.1.1.3.2 Are capacitors in Vinku (N7501) regulator lines working correctly?
VREG1: C7543
VREG2: C7547, C7548, C7554, C7555, C7553, C7552, C7558 and C7567
• Check that components are in place and solder joints are ok
• Disconnect the power supply from the phone and use an ohmmeter to check that regulator
lines are not short-circuited to the ground. If short-circuit is found replace capacitors
mentioned above. If this does not help go to the next step.
3.1.1.1.3.3 TX VCO (G7502) ok?
3.1.1.1.3.4 Replace Vinku (N7501)
3.1.1.1.4 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
3.1.1.1.4.1 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.
3.1.1.1.4.2 Replace Retu
3.1.1.1.4.3 Replace Hinku (N7500) or Vinku (N7501) or VCTCXO (G7501) or all three components
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Appendix A: RF Troubleshooting
A-25