On Sunday, June 10, 2018 at 1:07:02 PM UTC-5, wrote:
Hi,

This TV, located in the basement, is connected to a power strip with a
switch that "disconnects" everything that is plugged into the power strip..

I normally keep the power strip switch in OFF position. Recently, when
I turned it on (power strip), not long afterwards, the TV started to turn
itself on, then off. Then it repeated that "activity".

John


On Sat, 9 Jun 2018 20:44:42 -0700 (PDT), ...

OK, there are a million things that can turn it off but few that can turn it on. You might have bad little suppression caps or diodes at the keypad on the unit. They get intermittently leaky and can cause this. One way to find out is to power the unit up with the keypad disconnected. If it still comes on by itself it is either noise in the IR receiver or a bad uProcessor.

In many newer sets the keypad and IR receiver are on the same board and disconnecting one also disconnects the other rendering the test only conclusive to prove the uProcessor is good - if the behavior stops, though the caps and diodes may be on the main board in which case it is more logical to eliminate the noisy IR receiver first. To do this you'll have to unsolder it and remove it, and see what happens of course.

An IR receiver causing this is not unheard of but is a bit rare. It depends on how they structured the pulse trains in the system.

Assuming it does not stop without the IR input, you can remove those caps and diodes, lift one end unless they are SMD. When they are removed observe static handling methods, touch the unit before operating anything on it as it will be vulnerable. But if the behavior stops all you need is diodes and caps. Actually though it could be the glue underneath, but to prove it you pretty much ruin the components anyway so, you need them.

Unless the uProcessor is bad. That is pretty much a death knell for those things. It is unlikely you can get one and who knows, it might be BGA which quite frankly is not worth the trouble to change. They give away working TVs on Craigslist. I am only here because I firmly believe that anything that does not go to the dumpster is good for us and good for our country. It is worth a try unless one is too busy.