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

I recently 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 ranges. The backlight control voltage was also stable at 5V. The power supply board was a combined backlight power supply board, model 168P-P42ALM-00. After some analysis, I suspected the problem might be in the backlight signal board. I checked the components on the small signal board and found that the integrated circuit OZ9926AGN was likely the culprit. Consulting the datasheet for the IC, 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 faulty component. Upon inspection, I found that the external capacitor C4 connected to this pin was leaking. I replaced it with a new one, and the TV immediately returned to normal operation. The backlight started working correctly, and the screen no longer turned off after a few minutes. It's a good reminder that even small components like capacitors can cause major issues if they fail.