General Instructions For Cellular Rf Troubleshooting - Nokia RM-626 Service Manual

RM-626
Cellular RF troubleshooting

General instructions for cellular RF troubleshooting

Most RF semiconductors are static sensitive
ESD protection must be applied during repair (ground straps and ESD soldering irons).
Measuring equipment
All measurements should be done using:
• An oscilloscope for low frequency and DC measurements. Recommended probe: 10:1, 10 Mohm//8 pF.
• Aeroflex (Willtek) 440x/3100, Rohde & Schwarz CMU-200 or CMW-500 radio communication tester.
Note: A mobile phone WCDMA transmitter should never be tested with full TX power (permitted
only if measurements and tests are performed in an RF-shielded environment). Even low power
WCDMA transmitters may disturb nearby WCDMA networks and cause problems to 3G cellular
communication in a wide area.
Note: All measurements with an RF coupler should be performed in an RF-shielded environment
because nearby base stations can disturb sensitive receiver measurements. If there is no possibility
to use an RF-shielded environment, testing at frequencies of nearby base stations should be avoided.
Note: All communication test set screen dumps are from CMU-200. Other testers are different.
RF auto tune
Cellular RF parameters should always be re-tuned by means of Testing and Tuning Tool if one or more of the
RF components have been changed or memory (D3000) is corrupted.
RF shield cans
Once a peel-off type RF shield can is opened, a repair lid (Nokia code 9501325) should always be installed.
RF shielding does not work at all if RF shield cans are left open.
Level of repair
The scope of this guideline is to verify functionality of the cellular RF block as well as possible without
removing RF shields.
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