"DaveC" wrote in message
...
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.

Look for bulging capacitors. 2006 was the era of bad caps out of China. If
you have a scope look at the output of all voltage regulators for excessive
ripple.

Rick