Incorrect Pll Frequencies; Vctcxo Troubleshooting - Nokia 6275 Rf Description And Troubleshooting

Nokia Customer Care

Incorrect PLL Frequencies

Following are some possible causes for incorrect PLL frequencies:
• Power supplies to PLL portion
• Control line to VCO
• Loop filter or resonator components missing or incorrectly installed
• 19.2MHz reference clock missing or low
• Component failure (PLL IC, Rx Front-End IC, Tx IC, VCO, or VCTCXO)

VCTCXO Troubleshooting

• VCTCXO frequency is 19.2MHz. Without 19.2MHz, the mobile terminal does not
power up. This signal goes to the N7100, N7000, D2800, and the UHF PLL. Check
the test points in
• Check for the presence of the signal at the following points:
• F_REF_TX, clock reference to TX RFIC, should be ~ -9 dBm
• F_REF_RX, clock reference to RX RFIC, should be ~ -9 dBm
• CLK19M2_TIKU, clock reference for BB, should be ~ -9 dBm and ~2 dB less
in the other side of R7206
• If there is no VCTCXO signal at any of these points, check the voltage at VR3. The
main supply line for VCTCXO should be 2.8VDC.
• The AFC voltage should be between 1 and 3 Volts and should be adjustable with
the AFC slider on the RF PDM Control in Phoenix.
• If the AFC voltage is missing, check the UEMEK.
Issue 1 - September 2006
Figure 31: Phone Control dialog box
Figure 32 for the presence of the 19.2MHz signal.
Company Confidential
6275/6275i (RM-154)
RF Description and Troubleshooting
Page 37