Jun 26, 2023, 1:00 PM
Post #1 of 3
Sharp Aquos LC-52D85UN
I have a really bizarre problem (doesn't everyone on here)? :)
I'm trying to repair a TV that was handed to me for FREE.
It's a Sharp Aquos LC-52D85UN. Here are the symptoms:
The TV turns on perfectly fine, I can switch channels, switch input and all seems well, until it mysteriously turns off. 10 seconds or so later, it turns on by itself. A random amount of time later (seconds), it turns off again, and so it goes.
The original owner got rid of it because of that same issue. I've done a factory reset, and there were no changes in symptoms. I've gone into the service menu, and there don't appear to be any errors detected. I've taken a look at the power supply, and there is no bulging on the electrolytic capacitors (they're all clean). I've looked at the wiring connections, and they all seem to be ok. No discoloration on the board around resistors / diodes / transistors.
No blink codes present.
When the TV comes on, the screen looks good, and I can even go into the demo mode, and it stays displaying it for a bit, before it shuts down on its own again.
I've unplugged the control buttons off the side, to ensure it wasn't a depressed button, and it still turns off on its own.
I'm thinking it's a component in the power supply, or the main board is telling the PS to turn it off for some reason, but if it was the main board, I'd suspect that I'd see some sort of blink code. So I'm focusing on the PS itself, thinking that some component is causing it to abruptly shut off before the main board even has a chance to detect anything / write it to EEPROM.
I did look for a PS online, and even the same TV to do some swapping of boards, to debug that way, but it's nearly impossible to find this stuff (TV is something like 12 years old). The PS board is RDENCA336WJQZ.
There is an IC (TNY264PN), that is responsible it seems (based on the reference sheet), for detecting over current, temperature and a bunch of other things, but I don't have any reference from a good board, so can't confirm the measurements across any of the leads.
I'm a pretty stubborn guy, like the thrill of getting something repaired instead of throwing it out, and I'm good with soldering, but I don't know what to look for in this case. Most of these TVs seem to have the problem of not turning on at all, but I'm yet to see someone complain about the issue I'm seeing.
I found the service manual, but it's useless.
If anyone has any ideas, I'm all ears. Thanks!