Question

Samsung LCD TV problem

Model# LA40A550 mfg date 2008, The TV works OK when it works. it will start ok for an hour or so, then the screen shuts down with audio.
after the screen turns black it will not turn on by itself. i need to turn it off wait for a while and then again it turns on ok but not for long.
I have looked at it while dark with a flashlight and can see a faint video picture.
I have opened the back and looked at the Caps , they look OK, not swallwon or anything strange, i also checked the connectors and they are all in place. I need some advice what to do next, which and how board to test , as i am trying to fix it by myself due to shortage of funds, cheers.
Thanks for all

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Answer
That's the big clue -> "an hour or so"

Are you keeping the vents clear with canned air every year?

Why I ask is because I find most folk unaware that these devices need a little yearly maintenance.
Bob

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(NT) yep , its clean from dust and well ventilated TV.
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Then it needs service.

And the big clue is that one hour or so. Just like most electronics a part is heat sensitive so your tech would either swap a board or inspect the boards for a heat sink that isn't quite down tight. I've even found heat sinks with no compound on them (or thermal pads.)

What type of service you arrange for varies with your experience and skill. For me, if it's way out of warranty I'm pretty fearless since I design electronics so I'll go in. But most folk are stuck with the call for service.

That canned air? I've found it to pay off even when all I do is pull the cover and blow out the dust bunnies inside.
Bob

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heating problem

Hi,

hanks for the insight. as i opened the unit i did see several heat sinks mainly in the power unit.
But i do not remember any on the inverter board. do you thinks it maybe suffer from overheating too?
At short, which component or board to look for heating problems?

Thank you for all the help.

Doron

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OK, we're going in.

Remember that we don't get access to schematics or service manuals any longer. And even if you did, it would have a flow chart with you replacing boards.

For me, I would have the power removed and never touch anything with a bare finger while holding onto the cold water pipe. In other words I practice the "one armed" repair method so I don't get zapped. This is my only warning and this and any risk is yours to assume.

With that out of the way, I look for any BAD CAPS -> See BAD CAPS on google.com then I look for any heat sink that looks like I can pull off easily. I pop those off and see if the paste was missing or if they use a heat transfer pad and take action accordingly. The pads I'll just give the metal part a quick wipe with a paper towel then reinstall it being sure it's on properly.

For the thermal paste jobs if I see it's all dried up I'll wipe as much off as I can (this does not have to be perfectly clean of old paste) and then apply fresh compound and then button it down again. It must be flush and on proper or you see issues like this.

-> You ask how to find the heat sensitive part. There are two common tech tools to do that. One is the heat gun where you warm up parts and the other is freeze spray to instantly cool a part to see if that one is the one.

This is all stuff you learn in the trades.
Bob

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