Nokia Customer Care
Appendix A: RF Troubleshooting
A-36
Company Confidential
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2005 Nokia. All rights reserved
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GSM1800/GSM1900:
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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.
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Maximum power level – Output level should be about -25…-35 dBm
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Minimum power level – Output level should be about -55…-65 dBm
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Check if output levels of Vinku are as expected.
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NOTE!
If VINKU ASIC is transmitting wrong TX power just in one or two GSM-bands, typically
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?
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See section
“RF operating voltage VBAT_ASIC ok?”
3.1.2.1.2 Are Vinku (N7501) regulator voltages VREG1, VREG2 ok?
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GSM transmitter has to be active before VREG1 and VREG2 voltages can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
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Measurements can be done with an oscilloscope and a probe.
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VREG1: Connect the probe to C7543
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VREG2: Connect the probe to C7548 (or C7547)
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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?
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GSM transmitter has to be active before Vinku’s RB_EXT voltage can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to R7521.
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RB_EXT voltage should be 1.325 – 1.375 V.
3.1.2.1.2.1.1 VREFRF01-voltage ok?
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Measurement can be done with an oscilloscope and a probe.
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Connect the probe to R7503.
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VREFRF01 voltage should be 1.325 – 1.375 V. Typical value is 1.35 V.
