The cause of the fault may be sending bad channel work. The fax machine has a Modem (Modem) test function, can use this function to send the channel. Its operation steps are as follows: according to "FUNCTION" in turn (FUNCTION), "#", "1", "9", "3", "4" button to enter TECH (technology), then press "FUNCTION", "6" button to enter TEST mode, press "YES" to choose the TEST project, chose to "Modem TEST" after TEST (Modem), press "YES" to choose "FSK TEST" (frequency shift keying TEST), then press "YES" to enter FSK (frequency shift keying) signal TEST state. 2Viservice manual download site
 2Viservice manual download site
With the oscilloscope observation on the motherboard connector P2 17 feet signal waveform; If the signal is normal, then FSK signal is normal; Without should inspect and replace the signal system of related components, ensure the normal order of the FSK signal. Observation of integrated circuit U14 again (3), (4), pet-name ruby foot signal waveform; Pet-name ruby feet should be high level, (4) feet for sending graphic signal input, (3) feet for sending graphic signal output option. As pet-name ruby, (4) feet signal are normal, no signal, and (3) feet may be U14 (TC4053BF) internal damage. After replacement of U14 troubleshooting.2Viservice manual download site