Synthesizer Troubleshooting - Nokia 6275 Rf Description And Troubleshooting

Nokia Customer Care

Synthesizer Troubleshooting

Faulty synthesizers can cause both Rx and Tx failures during tuning, in addition to the
VCTCXO tuning. However, first check for the presence of various LO signals and their
proper levels. If everything fails, it may be necessary to check the reference clock
(19.2MHz) which is needed for the mobile terminal to power up. The 19.2MHz signal is
also important because the D2800 is sensitive enough to pick up a very weak 19.2MHz
clock, resulting in intermittent problems such as a constant mobile terminal reset.
Following are the synthesizers used in the mobile terminal:
• Dual-band UHF (1009.62MHz for channel 384 in Cell and AMPS bands, and
2088.1MHz for channel 600 in PCS band) with a separate LMX2310 PLL IC
• Rx VHF (256.2MHz for Cell, AMPS, and PCS) with PLL inside the Rx Front-End IC
• Tx UHF (3296.16MHz~3395.88 for Cell and AMPS, 3700~3819.9MHz for PCS)
with PLL inside the Tx IC
Issue 1 - September 2006
RF Description and Troubleshooting
Company Confidential
6275/6275i (RM-154)
Page 33