Let me talk about it: I am not professionally repairing LCD TV. I mainly repair the inverter, servo drive industrial machine, because there is a friend who is engaged in appliance repair, so he often has him to make LCD TV switch power board and control board. Let me help him repair, oh~~ I am generally helpful. Universal Back Sticker, Back Film, TPU Back Sticker, Back Skin Sticker, PVC Back Sticker, Back Skin,Custom Phone Sticke,Custom Phone Skin,Phone Back Sticker Shenzhen Jianjiantong Technology Co., Ltd. , https://www.jonsun-sz.com ! Hereby write and write the maintenance experience, share with you~~
When he sent it, there was no whole machine. Just give me a power board. He said that when he just opened it, there were a lot of small strong (蟑螂) power board boards that were all burned by voltage. I said this. It’s too big, I ran to the TV set, maybe the weather is cold~ I need a warm place~~哎~ He said that the power board is partially short-circuited, the FET is short-circuited, and he changed the burnt parts himself. Go to the machine test, can boot, the indicator light is on, but the backlight is not bright, he has not got the result for a long time~ So let me help~~ I took a look at the chip resistor after burning. Such a small component, and then measured whether there is a short circuit (prepare to do the work first) to determine no problem, power on, must first touch the hot components first ~ the power board is using FAN7930 power chip After confirming that no components are hot, short-circuit +5vb and PON, forced boot, the output voltage +12V+5V is no problem~ The voltage is normal, it is estimated that the high-voltage output voltage is not, and the voltage of the high-voltage output is 0V. , I found the power board circuit diagram online. FAN7930 6 feet (GND) and 8 feet (VCC) are 0V, INV is 2V, and found the data of 7930 chip, I think VCC should have more than 10 V voltage is normal, look at the circuit diagram is to find that the high voltage circuit should There are also starting conditions ~ Is there a switch that is not turned on, follow the circuit, and check the information, it is really necessary to put the +5VSB PONBK/on three feet together, it seems that I just started short-circuit forced boot ~ But the high voltage part is not open, the high voltage circuit has signal feedback and other circuits do not work, then the three legs are shorted together, the high voltage output circuit, no voltage is 0V, maintenance is in trouble, is it shorted wrong, or the circuit Still have problems! (It is not a professional LCD TV, so all aspects of experience and information are limited) I turned around and looked at the circuit diagram. I found that the FAN7930VCC pin was directly connected to the LEDVCC after passing through the triode. I immediately measured the VCC voltage to 9V. I just started the VCC without voltage. Now it is 9V, and immediately disconnects BK/ON, VCC. It is 0V, the original short circuit is correct, the high voltage circuit has been turned on, but why is the high voltage still no output? Also think about the 7930 VCC pin output should be more than 10 V, is it that the 9V excitation voltage is not enough, resulting in the triode is not conducting, the circuit does not work? ? ? Immediately let friends buy FAN7930, installed the amount of VCC voltage is 15V, psychological stealth, turn the amount of high-voltage output voltage, 100V, the end of the repair! The friend took it back to the machine and showed normal, no problems!