Nokia NPD-1 Series Troubleshooting - Rf page 14

NPD-1
Troubleshooting — RF
measured without taking the phone apart.
The result is a PDM value for the AFC DAC, which must be within +/- 150, which corre-
sponds to 2.2 v on the VCTCXO control pin (pin 1) and the carrier centered within
+/- 100Hz. The VCTCXO must be able to be centered within a certain voltage range in
order to allow for aging of the crystal (the centering voltage slowly drifts over time and
the phone will eventually run out of voltage range if it begins too close to the edge of
the range).
Manual Verification: Using the RF Main Mode window in Phoenix, turn on the PCS trans-
mitter, and set it to channel 600. Do not add any modulation.
Using the RF Tuning window, set mode=RF Tuning and choose this tuning. Look for a
transmitted tone on the spectrum analyzer at 1880 MHz. If no tone is present, proceed
to Troubleshooting section.
Center the carrier to within +/- 100 Hz of 1880 MHz. (If sidetones are present, be careful
to center the carrier and not one of the sidetones, which will probably have a higher
amplitude than the carrier.) The values you enter in the "values" edit box are the AFC val-
ues which control the VCTCXO frequency. Start with a value of 0, then adjust until it is
centered, staying within the limits.
Troubleshooting:
1) If there is no tone, probe pin 3 of G501 for a tone at 19.2 MHz. If this is not present
check power supplies, particularly ensure 2.7v on VCTCXO Vcc pin, pin 4 of G501. Also
check the control pin, pin 1 of G501, for a voltage between 0.4 and 2.7 v. If the voltages
are correct, and soldering of all G501 terminals is correct, replace G501. If 19.2 MHz tone
is present but tone at 1880 MHz is not, troubleshoot PCS TX chain as described in the
Probing Diagrams section.
2) If the carrier is present but the PDM needed to center it is outside of the +/- 150
range, or if it cannot be centered, there is a hardware problem.
3) In the following procedure, performing frequency centering on the RF carrier at
1880 MHz will detect frequency errors due to the VCTCXO and supporting hardware,
which will be the majority of the problems, but will not detect frequency errors due to
the hardware that mixes the VCTCXO tone at 19.2 MHz up to 1880 MHz. In order to
troubleshoot this hardware also, frequency centering should be performed on the
19.2 MHz tone to +/- 19.2 Hz on pin 3 of G501 using a frequency counter, then the VHF
and UHF LOs should be checked. Since this will be time-consuming and will probably
only account for a small percentage of the failures, it is not recommended unless the sit-
uation justifies the time spent. The VHF LO is inside the Robin IC (N601) and trouble-
shooting of the cell UHF LO is according to Table 2.
4) If the carrier can be centered but the PDM is out of range, check the control voltage
on pin 1 of G501. If it is 2.2v, (and pin 4 is at 2.7v, and pin 2 at 0v), then the VCTCXO
(G501) is working correctly but the circuit that delivers the control voltage is not. Check
Page 14
Nokia Corporation
CCS Technical Documentation
Confidential Issue 1 11/2002