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

LED Light-Emitting Diode

A user brought in a Konka LCD TV model LED26F2200CE, stating that it was working fine until they heard a "pop" sound. They mentioned the repair cost was too high and were considering discarding it. After disassembling the unit, I found a 3-in-1 motherboard, which made me think replacing the board wouldn't solve the issue. Upon inspection, I noticed that the peak absorption capacitor CW912 (101P/2KV) in the power supply section had burned out, leaving a black hole. Removing it revealed that the switching transistor VW901 (7N65) was shorted. The Zener diode VDW929 (6.8V), which protects the switch tube from overvoltage, was also damaged. Additionally, the fuse F901 (3.15A/250V) had opened. The gate drive circuit for the switch transistor appeared to be intact. I replaced the faulty components: the peak absorption capacitor, the Zener diode, and the fuse. Then, I checked the power IC’s pins. The voltage on pin 6 fluctuated around 12V, and pin 5 showed about 1V, indicating the power IC was likely functioning properly. After disconnecting the power and discharging the 300V DC capacitor, I installed a new switch transistor (7N65). The TV powered up successfully, and all functions worked as expected. Based on the analysis, it seems the peak absorption capacitor failed due to a voltage spike, causing the Zener diode to break down. The current-limiting resistor (0.3Ω/2W) remained intact, but the switch transistor failed due to the short caused by the Zener diode. This led to the fuse blowing, resulting in no power to the system.