Nokia 6680 RM-36 Service Manual page 282

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• GSM1800/GSM1900:
Connect the RF probe to C7577 or C7575. The level should be about the same on both capacitors.
-
Check output level with at least the maximum (0) and the minimum (15) power levels.
Maximum power level – Output level should be about -25...-35 dBm
-
Minimum power level – Output level should be about -55...-65 dBm
-
• Check if output levels of Vinku are as expected.
• NOTE!
this means that Vinku ASIC (N7501) is faulty or the ASIC is badly soldered. Of course SAW-filter
Z7504 or balun T7502 can be also faulty/badly soldered and causing short-circuit, but probability
to this is quite low. For example: VINKU is transmitting too low power in EGSM900-band but TX-
power is ok in other GSM-bands. Then it's almost clear that VINKU (N7501) is faulty or badly
soldered and the component should be replaced.
3.1.2.1.1 RF operating voltage VBAT_ASIC ok?
• See section
3.1.2.1.2 Are Vinku (N7501) regulator voltages VREG1, VREG2 ok?
• GSM transmitter has to be active before VREG1 and VREG2 voltages can be measured. Procedure is
explained in section "Transmitter troubleshooting".
• Measurements can be done with an oscilloscope and a probe.
VREG1: Connect the probe to C7543
•
• VREG2: Connect the probe to C7548 (or C7547)
• VREG1 and VREG2 voltage levels should be 2.65 – 2.86 V. Typical value is 2.7 V.
3.1.2.1.2.1 Vinku (N7501) RB_EXT voltage ok?
GSM transmitter has to be active before Vinku's RB_EXT voltage can be measured. Procedure is
•
explained in section "Transmitter troubleshooting".
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to R7521.
• RB_EXT voltage should be 1.325 – 1.375 V.
3.1.2.1.2.1.1 VREFRF01-voltage ok?
• Measurement can be done with an oscilloscope and a probe.
• Connect the probe to R7503.
• VREFRF01 voltage should be 1.325 – 1.375 V. Typical value is 1.35 V.
A-36
If VINKU ASIC is transmitting wrong TX power just in one or two GSM-bands, typically
"RF operating voltage VBAT_ASIC ok?"
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Appendix A: RF Troubleshooting