User Guide

Nokia Customer Care RF Description and Troubleshooting

6235/6235i/6236i (RM-60)

IMPORTANT: You must check for both conditions before replacing the chip. If you

have no LO signal, refer to "UHF Synthesizer Troubleshooting"onpage52. If you have a

significant supply voltage drop on one of the supply pins, then replace the N7160.

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

Table 6: N7160 Conditions and Supply Currents

Condition: Local Mode, Set

Rx Only in RF Main Mode

Supply Current

(From Power Supply)

Good mobile terminal 100mA

No UHF LO signal present 254mA

Pin 13 shorted 255mA