Xiahua plasma TV PS-42K8 soundless maintenance example - appliance repair - Huaqiang electronic network

Fault phenomenon: There is sound, no grating.
Overhaul: Check that the output voltage of each power supply board has no Vs voltage, and the other voltages are basically normal. Disconnect the Y board, and the Z board still has no Vs voltage output. Initially detected Y, Z board no obvious failure. Determine the power board is faulty. There was no obvious short circuit in the test power board, and the road was opened. No signs of burning and burning were found by visual inspection. Repair welding (large area) power board test machine, grating appears, want to further detect the relevant voltage when the black screen, or there is no Vs voltage, indicating that there is a bad contact! Focus on checking the PFC voltage - 380V is normal, check the Vs drive IC203 (IR2109) 1 pin voltage -14V. Relatively low, the power supply is supplied by IC202--KA7815, repair welding IC202, IC203 test machine grating appears. But the time is not long and the screen is black again. It is suspected that the filter capacitors C222 and C223 associated with the KA7815 are unstable due to high temperature, so the two capacitors are replaced again, but the test machine is still black. Check IC203 (IR2109) voltage 1 pin 14V, 2, 3 feet no driving voltage, 4 feet grounding, 5 feet 13V, 6 feet 10V, 7 feet 12V, 8 feet 16V, (data shows 8 feet 24V or so, normal measured voltage 75V ) Suspected that the drive unit CN8100 is defective. Because the board can't be repaired if it is not removed.
Carefully remove the driver plate carefully repair welding, test machine - repeated test machine grating has been normal.
It is worth reminding that the board is a double-sided circuit board disassembly must be careful, if it is not good, it will remove the plug hole, which will cause more trouble.