Synthesizer Troubleshooting - Nokia 6235 Troubleshooting Manual

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IMPORTANT: You must check for both conditions before replacing the chip. If you
have no LO signal, refer to
significant supply voltage drop on one of the supply pins, then replace the N7160.
Condition: Local Mode, Set
Rx Only in RF Main Mode
Good mobile terminal
No UHF LO signal present
Pin 13 shorted

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 processor 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 N7100 IC
• Tx UHF (3296.16MHz~3395.88 for Cell and AMPS, 3700~3819.9MHz for PCS)
with PLL inside the N7000 IC
Issue 1 04/2005
"UHF Synthesizer
Table 6: N7160 Conditions and Supply Currents
©2005 Nokia Corporation
6235/6235i/6236i (RM-60)
RF Description and Troubleshooting
Troubleshooting" on page 52. If you have a
Supply Current
(From Power Supply)
100mA
254mA
255mA
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