Uhf Synthesizer Schematic; Uhf Synthesizer Troubleshooting - Nokia 6275 Rf Description And Troubleshooting

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UHF Synthesizer Schematic

UHF PLL IC

UHF Synthesizer Troubleshooting

The UHF LO frequency varies with the channel and can be calculated using the Frequency
Calculator dialog box in the Phoenix RF component. Use the following steps to
troubleshoot the UHF LO frequency.
1. Ensure that the LO is locked. Set a channel and check the output of the UHF LO
at L7201 within a very narrow span of 100KHz. The LO must be virtually
immobile.
2. Measure the nominal UHF LO signal levels (see
test points" on page 38).
3. If you do not see the presence of any LOs, check the DC voltages at the following:
• R7216, VR1A, supply line for UHF PLL IC = 4.7VDC
• R7200, VR4, supply line for VCO IC = 2.7VDC
4. Ensure that the lock voltage at C7217 is between 1V and 3V.
Issue 1 - September 2006
Loop filter
Figure 37: UHF Synthesizer Schematic
Company Confidential
6275/6275i (RM-154)
RF Description and Troubleshooting
Dual-band
UHF VCO
"VCTCXO and UHF Synthesizer
Lock voltage
Page 41