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Use oscillograph check the power supply voltage 4.9V G800 Lo normal. Check the G800 1 foot (PLL error voltage control feet) none, pulse appears suspect N505 if modules have a cold solder joint or damage, welding N505 fault remains. N505 removed, reballing back into the phone again, boot a network number and the signal bars, and troubleshooting.wTbservice manual download site
Summary: failure due to N505 PLL phase detector failed to enter work, G800 can't get correct voltage phase-locked control, fail to produce the required local oscillator frequency signals, using oscilloscope measurement of phase-locking error voltage to determine fault location.
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