Repair Changhong LCD TV 3D42A3700iD three failure-free one case - Home Appliances
On March 2nd, a customer came to the store and called Xiaofu to repair a TV. After visiting the user's home, I saw a PDP TV mounted on the wall — a Changhong 3D42A3700iD. The issue was that it suddenly went dark, with no backlight. It had been broken since last year but hadn’t been fixed yet. After disassembling and doing a quick test, I found that the fuse was intact, and there was 300V voltage, but it couldn’t be released. I checked the first few components and they all looked normal. I wanted to take the power board home for further testing, but I was worried about other potential issues. After discussing with the user, we agreed that I would take the TV home for three days and return it. The price was orange green brown (a local term for a negotiated price), and the user agreed.
During my hands-on inspection of the power supply board [PSPF251502A], I noticed that the first pin of the ICB801SD was blown. One foot of the CB801 capacitor was rusted and broken, and the QQ806 transistor had three pins rusted and broken. I removed the IC [3BR2565JF] and measured it, finding a short circuit, so I scrapped it. Then I tested the QQ806 [STD5915] and found the pins were open, meaning no continuity. The back of the board had some traces of stripping and mildew. I cleaned the board using water, removed the paint, and used a TB tool to check the board. The new 100V part wasn't worth shipping, so I decided to buy a total of 14 yuan for the power supply ICs and planned to fix it myself.
I started by searching for the STD5915 transistor on the old board, but couldn’t find it. I checked online forums but didn’t find any alternatives. Eventually, I found some information on Marco Polo and learned that D13007 could be a suitable replacement. I looked through several power boards and found only 13001 and 13003 models. Later, I went to a town in Nikko and searched for a D13007. I compared the pin order of the TO-92 package and the original one. I noticed that the casing was connected to the C terminal. I drilled a hole in the heat sink of the power IC, applied silicone grease, and fixed the component with cloud-like material. I then used a thin wire to connect it back to its original position.
The CB801 capacitor was a 222/800V polyester type, and one of its pins was broken. I replaced it with a 472/2kV ceramic capacitor. After completing this part, I let it rest for three days. When I received the TV back, I installed the new 3BR2565JF IC with silicone grease, turned it on, and it worked — 5V output was stable. When I pressed the power button, the screen lit up normally, with no snowflakes. I tried playing a DVD, and the picture was clear. The user said “orange green brown†again, and I offered a one-year warranty. 😊
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