Power up test machine, 115V power supply output is about 30V. Disconnect the power load, connected to the main power supply filter capacitors C822 115V system a 60W light bulb, bulb small red, measuring voltage 30V. Light bulb suddenly brighter at the instant shutdown before turning off, indicating the power supply itself is not normal. Repeatedly to boot, found that sometimes works, but often had to wait for almost more than 10 minutes. If you shut down moments before the light bulb was not completely extinguished and boot, work, main power supply adjustable output between the 103~132V.
This machine uses a modified Toshiba X56P switching circuit. Switch V806c is 300V normal logging, but b is +1.2V, and normally should be around -2V, of rectifier circuit and R808 R809 R804, R803 circuit consisting of normal faults should appear in the pulse width adjustment circuit. If switching feedback circuit comprising T803 11~12 winding of a transformer is faulty, the boot will be no voltage output, but the current voltage of 30V, V806 is starting only conduction time or frequency risked. Estimated to be made up of V811, V812 and peripheral components due to pulse-width control circuit is not working properly. Focus on this part of the circuit. Finally, through detailed examination, V812 former repairman replaced the C3807 and original use C1959. After you change into a new one, and troubleshooting. But new C3807 machines, failure to reproduce. Search C3807 has superior parameter C1959. DT9508 digital watch measuring C3807 β value of 1860, C1959 β β β with the value 189,C2500 with value 114,C1815 value is 145.