LCD TV turns off after 5 minutes?

I think the LCD is “toast”. Expensive to fix, maybe but not sure. The electronics could be bad or the LCD panel itself. If there is sound it most probably is panel or the video driver circuit.

I had a Samsung that did that too. I did a search for the particular model and discovered I was not alone. There was a fix but it was so complicated and labor intensive it was not worth it. I threw it out and made a promise to avoid Samsung for my next purchase.

Did the sound quit also? Does it turn off after 5 minutes, even if you are changing channels?

It could be a thousand things… but remember it’s turning itself off as a safety precaution.
There’s no simple solution unless you are an experience technician.

(*Have you though of telling the little guy inside the TV to cut it out ;-)

Might not be a safety precaution, it might be mistakenly going into a sleep mode ?
It could also be the power supply failing. That might not be so hard to fix/replace.

Both sound and video go out. Power related. Any thoughts? Specifically a troubleshoot method

I’ll first assume you have explored any sleep mode settings that might be available, and disabled them or set them for a long period.

Open it up. Check connections on the power supply and output voltages on the power supply.

Run it until it goes dark again and re-check those voltages.
If they are the same as before (i.e. non-zero) then it’s not the power supply.
If some of the power levels have flatlined then that’s your culprit.

The fact that the power light stays on is weird and suggests that if it is a problem in the power supply it’s only partially fried. But that is entirely possible as it probably puts out multiple voltages independently.

Since the sound goes out too, that suggests it’s not just the power to the backlight (cold-cathode flourescent tubes probably have their own distinct part of the power supply output).

There could be a lose connection between the input and all the video and audio output sections. Are there alternative inputs you can put the signal into?
Can you try another source (e.g. a laptop? old VCR? stand-alone DVD player?) and see if it behaves the same or differently ?