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Disassemble, powered on after startup, use oscillograph check U501 Lo module 15 foot and found it 13MHz signal amplitude is very small. Check U500 3 feet, have the normal range of 13MHz signal. Refer to figure 4, find 13MHz signal paths, R507 resistance increases. At about 120K, normal values for the 1k, after changing R507, troubleshooting.ngZservice manual download site
Summary: U501 internal PLL circuit failed to join the normal reference frequency signal discriminator cannot be compared, does not properly control the vibration frequency, resulting in cell phone power on no signal.
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