No Power - Canon LV-7355J Service Manual

1. TROUBLESHOOTING

1.1 No Power

The possible causes of No Power are listed below. Please check following and refer to
power supply and protection circuits diagram in the figure opposite.
1) Stop the operation of power supply circuit due to detection of abnormality.
Detected the abnormality on the secondary power supply lines.
• Power failure detection diodes detect an abnormal voltage on the power supply.
Check the shortage of secondary circuits, IC, condensers, etc.
Detected the operation stop of cooling fans.
• Power failure detection diodes detect the fan operation stop.
Check Fans FN901, FN902, FN903, FN904, FN905 and FN906.
• Check fan's power supply lines and detection diodes and transistors D69A, D69B,
D69C and Q69A.
Detected the abnormal temperature rise inside the projector.
• Temperature sensor IC detect abnormal temperature.
Check peripheral circuits and sensor IC IC4881 and IC2881.
• Thermal switch (TSW611) detects abnormal temperature.
Check peripheral circuits and TSW611.
TSW611 ............................................... open in normal
TSW611 shorts when the peripheral temperature is over 90˚C.
• Thermal switch (SW902) detects abnormal temperature.
Check peripheral circuits and SW902.
SW902 ................................................. short in normal
SW902 opens when peripheral temperature is over 100˚C.
Detected the abnormality on the lamp ballast unit.
• The lamp ballast unit outputs error signal (LAMP_ERR) to pin 47 of IC801.
LAMP_ERR........................................... High in abnormal
Detected the over load/over voltage on power supply circuit.
• Feedback circuits detect over load or over voltages.
Check PC641, PC642 and peripheral circuits.
Operated the mechanical protect on the Interlock switch (SW904).
• Check lamp cover fixed correctly.
Fuse (F601) open.
4-1
Part 4: Troubleshooting