On Thursday, March 5, 2015 at 10:20:11 AM UTC-5, DaveC wrote:
Samsung HLS5087W rear projection TV, 50-inch, vintage 2006. This is one of
the "tabletop" rear projection models (about 14" deep) not one of the huge
particle-board cubes.

After being on for as little as 3 minutes or as long as 30 minutes it will
just turn off. No error code (no blinking LEDs) is displayed. It's like I
pressed the Power button. When I try to restart the TV it may or may not
start right away; it may take a few tries. (See startup attempt, below.)

It's not the remote--removing the remote's batteries, the problem still
happens.

The service manual lists 3 reasons for turning off:

1. Rear lamp door is opened. I checked the continuity of the rear door switch
(OK) and even bypassed the switch by soldering a jumper across the switch
terminals. No joy.

2. Temperature reaches 203 deg (F). The fans are operating normally so
there's no way this can heat up--randomly--to 203 in as little as 3 minutes.
I've blown the dust from inside so it's not that.

3. Lamp fails to turn on 4 times. This isn't the failure mode--the lamp is on
when the TV just turns off. And failure to turn on the lamp gives a failure
LED blink code, which I don't see.

An additional symptom: after turning off, when I press the Power switch I
hear the color wheel start up (it's a dull hum, constant speed) and
immediately there's an additional buzzing a slight variable pitch to it,
higher, less than 1khz(?). I don't think it's electronic like an arc or
transformer but like another motor.

What's causing this TV to turn off?

Thanks.

Shut down is a real pain in the ass. How does the picture look just before shut down? I'm not an expert but I have worked on some of theses. I don't think it's a door problem because it seems unlikely that it would take three minutes to sense this. I don't know about the other noise but I think that if it was related to the color wheel you would notice that in the picture. I would suspect something getting too hot somewhere. With the back off try a 20 inch box fan blowing into the set and see if that may increase the time before shut down. If it does after that you'll have to get a can of cold spray and hope to get lucky. Lenny