Appendix A: RF Troubleshooting
Nokia Customer Care
Company Confidential
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2005 Nokia. All rights reserved
A-22
3.1.1 Does GSM TX transmit RF-power at all?
•
If TX signal is not found at all use wider span setting and check if the transmitter is
transmitting on wrong frequency. If signal is found to be on wrong frequency or frequency is
not stabile,
see section 3.1.3. "GSM transmitter frequency correct".
3.1.1.1 Is Vinku (N7501) transmitting RF-power at all?
•
GSM transmitter has to be active before Vinku’s output level can be measured. Procedure is
explained in section “Transmitter troubleshooting”.
•
Measurements can be done with a spectrum analyser and an RF probe. RBW and VBW =
1 MHz, Span = 0, sweep time 1 ms. Spectrum analyser centre frequency should be set
according the used TX channel (see section “Frequency mappings”). Notice that GSM
transmission has pulsed nature and power should be measured during TX burst (triggering
needed). Another possibility is to use following settings: RBW = VBW = 1 MHz, Span 200 kHz
and sweep time at least 2.5 seconds.
•
GSM850/EGSM900:
-
Connect the RF probe to Z7504 input. The level should be about the same on both input pins.
Check output level with at least the maximum (5) and the minimum (19) power levels.
-
Maximum power level – Output level should be about -15…-25 dBm
-
Minimum power level – Output level should be about -45…-55 dBm
•
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!
If VINKU output RF-power is totally missing just in one or two GSM-bands, typically
this means that Vinku ASIC (N7501) is faulty or the ASIC is badly soldered. For example: VINKU
is not transmitting at all in GSM850/EGSM900-band but TX-power is ok in other GSM-bands.
Then it’s quite clear that VINKU (N7501) is faulty or badly soldered and the component should
be replaced.
3.1.1.1.1 RF operating voltage VBAT_ASIC?
•
Measurement can be done with an oscilloscope and a probe.
•
Connect the probe to C7503 (or C7501, C7541)
•
VBAT_ASIC voltage level should be 3.05 – 5.4 V. Typical value is 4.0 V.
Summary of Contents for RM-57
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