General frame to frame a line fault output IC, the power supply circuit, an oscillator called damage is common. This machine is powered by a normal investigation , ic601 53 feet oscillation waveform output is normal , IC451 also working point of the foot with an external signal injection IC451 1 foot grating appeared , so the focus of suspicion interface circuit IC401 failure problem , check the frame waveform really 17 feet no output , input is normal , and check their peripheral bus voltage operating point of each foot and no abnormalities, failure seems to be very clear , IC401 damaged, but replaced the IC401 fault persists, maintenance deadlocked.9Vwservice manual download site
       After careful examination blueprint analysis IC401, feel the impact of the internal frame signal at IC401 -off only bus actions, and subsequently review the bus voltage is normal , with an oscilloscope to see , even without waveforms along the check to the computer block IC1101 of 37.38 feet no wave , does not block the work of the computer ? carefully check IC1101 working conditions, found 25 feet RESET voltage of 0.5 volts, this pin is disconnected peripheral resistance as measured on the ground of its 3 ohms , significantly short circuit !

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