When repairing a Samsung UA32C400P, the technician noticed that the boot backlight flashes briefly before the screen goes black, though sound is still present. Upon opening the cover, the backlight was observed to flash occasionally or not at all. The power supply for this model uses a two-in-one board, with the backlight having its own separate power supply. This means a single transformer provides power specifically for the backlight, which is controlled by both the main board and the auxiliary power source. The voltage is first boosted to over 80 volts and then further increased to more than 140 volts. At the moment of power-on, the backlight voltage rises above 100 volts but then gradually drops to zero. Initially, I suspected a faulty backlight protection circuit. After disassembling and testing the backlight, it appeared to be in good condition without the screen. I thought it might be a connection issue. After fixing the plug, the backlight came back on, but it still wasn't bright. Then, I noticed that if the motherboard was disconnected from the side panel, the backlight would turn on, but the screen wouldn’t light up. When the backlight was on, the screen remained dark, and the backlight voltage dropped to zero. That was strange. The 12V to the screen and 5V to the motherboard were supplied by another transformer, and no abnormalities were found on the logic board. After checking the power board without the screen cable connected, I measured the voltage of the backlight power module W6052S. The voltage on pin 2 was 18.9V, which seemed a bit high. This voltage comes from the transformer that supplies power to the motherboard. Further investigation revealed that the ZDS806 regulator in this circuit was open. Testing the diode gear showed an infinite resistance in both forward and reverse directions. I replaced it with a 15V voltage regulator, reconnected the screen cable, and the TV booted up with sound and image. Once the voltage regulator failed, the W6052S supply voltage rose to a critical point. When the logic board was connected, the 12V load increased, causing the W6052S voltage to rise higher than other outputs from the transformer. The voltage reached just the protection threshold, which is why there was no backlight. That’s what was causing the issue! ! !
Diamond Core Drill Brazing Line
Diamond Core Drill Brazing Line,Diamond Core Drill Brazing Machine,Diamond Core Drill Brazing Production Line,Big Segment Grinding Machine
Suzhou Mountain Industrial Control Equipment Co., Ltd , https://www.szmountain.com