NSD–1
Disassembly / Troubleshooting Instructions
PAMS Technical Documentation
Page 20
Issue 2 09/00
Nokia Mobile Phones Ltd.
Trouble Shooting
The VCTCXO reference designator is G501. VR1 is supplies 2.7v to the
VCTCXO (TP101) through R501 and decoupled with C561. The VCTCXO
is controlled by a DC level from the AFC PDM in MAD connected to Pin
132. The PDM is filtered by R114 and C130 in the base band section and
by R504 and C507 in the RF section. Resistors R503 and R538 center
the PDM voltage. Typically a correctly tuned VCTCXO should have
approximately 2 volts on pin 1 (TP100).
Adjustment of the AFC PDM from 0 to 511 should result in a voltage
change on G501 Pin 1 (TP100) between 1.9 and 2.2 volts with a 10KHz
change in the transmitter output frequency in Cel or a 22KHz change in
PCS.
On SSP phones which do not have AMPS, clicking the “PCS AFC Tuning
On” box will disable the CDMA modulation allowing AFC tuning to be per-
formed on the RF carrier feed through.