Share Konka LED42F2200NF heat machine from time to time flash screen - appliance repair - Huaqiang electronic network
After testing the machine at the customer's home, after more than 20 minutes, the backlight will start to recover for a few seconds and then immediately resume. After a while, the backlight will flash continuously. When the brightness is lowered, the flash will be slower, and the minimum will not be flashed. I suspect the lamp bead problem and the machine pulls home. Mini Inverter,Mini Frequency Inverter,Compact Frequency Inverter,Ac Frequency Drive For Motor Zhejiang Kaimin Electric Co., Ltd. , https://www.ckmineinverter.com
After going home, turn on the power, measure the voltage of the two lamps 169.8V and 170.2V, backlight power supply 70V, and start flashing after about half an hour. When the lights flash frequently, remove the motherboard, use the fan to cool down, then install the boot, it is also flashing, this I believe that it is a problem with the backlight. The backlight of this machine is side-in, at the bottom, how to determine which side of the lamp is broken? I checked it on the Internet, I don’t know if I didn’t check it. The original backlight of this model has a common problem with the flash screen. The reason is that the lamp bead fires on the heat sink. The text says that the backlight IC (OCP8122A) is protected. The lamp beads are not working, but there is no way to protect them. I am too lazy to look for information. When I look closely at the backlight, there is no obvious dark area on the bottom of the screen! At this time, I was blinded. Do you want to dismantle the screen? Let go first.
Plugged in the next day, it took more than two hours to work, I wonder if I can test it unilaterally? I tried the backlights on both sides separately. They all flashed once after a few seconds of booting. After that, they didn’t flash. It’s impossible to have the same fault on both sides of the light bar! Isn't the problem not in the light bar, rethinking the whole test process, only one set of light bars can work, when the light bar is connected to the problem, the brightness will be lowered and it will not flash. Is this atypical load capacity poor? Is it a backlight boost circuit or a power supply? Measured the next 12V, 9V beats, obviously low, shutdown to pull off the backlight, 12V power supply 9.3V, backlight power supply 65V, how do I not pay attention to the power problem at first? Check the power sampling circuit and find that the resistance of the sampling resistor 564 powered by the backlight is only 312k. This should be the problem. For further verification, find a 500k adjustable resistor replacement. When the backlight is powered down to 64V, the backlight starts. Blinking, finally determined the fault point, find a 514 and a 513 chip resistor in series, start 12V power supply 12.2V, backlight power supply 86.8V, test machine no longer splash screen for half a day