Konka LCD TV LED26F2200CE three trouble-free maintenance examples - appliance repair - Huaqiang electronic network

LED light-emitting diode

A customer brought in a Konka LCD TV model LED26F2200CE, which was working normally at first. However, they heard a "pop" sound from the unit and mentioned that the repair cost was higher than the value of the TV, so they were ready to give it up. After disassembling the TV, I found a 3-in-1 motherboard. Replacing the board wouldn't help. Upon inspection, I noticed that the peak absorption capacitor CW912 (101P/2KV) in the power supply section had burned out, creating a black hole. Removing it revealed that the switching transistor VW901 (7N65) was shorted. The Zener diode VDW929 (6.8V), which is connected between the switch tube's S and ground, had also failed. Additionally, the fuse F901 (3.15A/250V) was open. The gate drive circuit for the switch tube appeared to be intact. I replaced the switch transistor, the peak absorption capacitor, the Zener diode, and the fuse. When testing the power IC, the voltage on pin 6 fluctuated around 12V, and pin 5 showed around 1V, suggesting the power IC was functioning properly. After disconnecting the power and discharging the 300V DC, I installed a new 7N65 switch transistor. The TV worked perfectly after that. Based on the analysis, it seems the peak absorption capacitor CW912 failed due to high voltage, which caused the Zener diode VDW929 to break down. The current-limiting resistor (0.3 ohm/2W) remained intact, but the switch transistor VW901 failed as a result of the short circuit through VDW929, leading to the fuse blowing. This resulted in three main failures: the capacitor, the Zener diode, and the switch transistor.