Skyworth LCD TV 42K08RD irregular black screen fault repair example - appliance repair - Huaqiang electronic network

MOS Power IC Full Range

Electronic Scale Crystal Oscillator 3.2*2.5mm 3225 16M (16.000MHZ) 12PF 10PPM 20PPM 30PPM

Inductance

Brand AVX TPSE226M035R0125 Low Impedance Tantalum Capacitor AVX 22

SMD Aluminum Electrolytic Capacitor

Recently, I worked on a Skyworth 42K08RD LCD TV that had a strange issue. The TV would boot up with normal sound and image, but after about ten minutes, the screen would go black. I opened the cover to check the power supply voltages—12V, 24V, and 5V were all within normal range. The backlight control voltage was also stable at 5V. The power supply board was a two-in-one design for the backlight, model 168P-P42ALM-00.

After some analysis, I suspected the problem might be with the backlight signal board. I checked the components on the signal board and found that the integrated circuit OZ9926AGN was acting strangely. Looking up the datasheet, I noticed that pin 17, which is responsible for detecting the 12V power supply voltage, was only reading around 2V instead of the expected 3.5V. This indicated a possible issue with the external capacitor C4 connected to that pin.

I removed the capacitor and tested it, and it showed signs of leakage. Replacing it fixed the problem, and the TV returned to normal operation. It's always surprising how a single faulty component can cause such an intermittent failure. The repair process involved careful testing and component replacement, which highlights the importance of thorough diagnostics in electronics repair.