C8 is impossible to charge wW

The under-voltage indicator light of the Chunlan cabinet-type air conditioner turns on after power-on, and neither the indoor nor outdoor units can work.

Maintenance process: First, check that the power supply is normal. Then, measure the voltages at pins 6 and 7 of IC, which are also normal. Next, check that pins 1 and 2 of IC1 are both at low level, indicating that the detection window of the voltage comparator is normal. From the circuit principle, it is known that when the under-voltage light is on, relay J must be activated. Then check the voltages at pins 10 and 11 of IC and across C8, and find that there is already a voltage charged across C8. When pins 1 and 2 of IC are at low level, C8 cannot be charged. After removing V4 for inspection, it is found that its c and e terminals are breakdown. The fault is eliminated by replacing it with an 8050 or 9013 transistor.

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