Preliminary Rf Troubleshooting; Mobile Terminal Cannot Make A Call; Tx Power Low - Nokia 6255 Rf Description And Troubleshooting

6255/6255i/6256/6256i (RM-19)
RF Description and Troubleshooting

Preliminary RF Troubleshooting

The following sections identify steps to troubleshoot some common RF issues.

Mobile Terminal Cannot Make a Call

Verify the following if the mobile terminal cannot make a call:
1. The mobile terminal is in Normal Mode (i.e., the mobile terminal is searching for
a signal, net server is on).
2. The Preferred Roaming List (PRL) is loaded into the mobile terminal.
3. The mobile terminal is tuned and has passed tuning. Read the tuning parameters
using the Read Parameters component in Phoenix. An untuned mobile terminal
has all zeros in the tuning file.
4. The call box channel is set for a channel in PRL.
5. The SID is correct and entered into the mobile terminal.
6. The VCTCXO is centered as described in the "VCTCXO Manual Tuning" section on
page 54.
7. The transmitter and receiver are working properly in Local Mode. See
"Transmitter RF Troubleshooting" on page 11 and "Receiver RF
Troubleshooting" on page 31 for detailed information.

Tx Power Low

Complete the following steps if Tx power is low:
1. Use Phoenix to turn on the transmitter in Local Mode.
2. Perform a visual inspection of the PWB under a microscope to check for the
proper placement, rotation, and soldering of components.
3. Look for the presence of a Tx signal on a spectrum analyzer at the correct
frequency.
• If a signal is present but off-frequency, check the synthesizers for proper
frequency and amplitude. One of the synthesizers may be unlocked or the
VCO has no output signal.
• If a signal is not present or is present but is low in amplitude, check the
probing diagrams to determine where in the chain the fault occurs. (See "Tx
RF Test Points - Bottom Side" on page 28.)
4. Ensure that the power supplies to the Tx have the correct voltage. (See "Tx DC
Test Points - Bottom Side" on page 25)
5. Ensure that the AGC PDMs are set for the desired Tx power and that the AGC
voltages are correct. (See "AMPS Tx Setup" on page 15, "Cell Tx
Setup" on page 18, or "PCS Setup" on page 20.)
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©2005 Nokia Corporation
Nokia Customer Care
Company Confidential Issue 2 05/2005