HDTV turns off

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DaveC 11 years ago

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:

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.

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.
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.

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captainvideo462009 11 years ago

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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 t hink 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 ti me before shut down. If it does after that you'll have to get a can of cold spray and hope to get lucky. Lenny

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John-Del 11 years ago

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It kind of sounds like a bad lamp. The additional buzz you hear is the bal last trying to strike the lamp. If it buzzes from a cold start and the lam p doesn't strike, it's bad. The problem with troubleshooting this problem is that if the lamp is hot, it won't restrike even if the lamp is good.

In Samsung DLP TVs, the trip voltage to shut down the ballast (and TV) is r oughly 140-141 AC. If the run voltage across the lamp hits this voltage, th e TV will shut down as the lamp is at the end of it's life. Note that if y ou leave your meter across the lamp while the ballast is attempting to stri ke the lamp, you'll destroy your meter, so measuring the voltage must be do ne carefully and only attempted when the lamp is actually lit. Don't defea t the interlock if you intend to look at the lamp running, as the UV will d estroy your retinas. If the run voltage is lower than 130, your lamp is OK, and the TV could be shutting down for a different reason.

In my experience, a lamp that is bad will reach max voltage in less than 5 minutes, so the fact that yours will sometimes run to 30 minutes makes we w onder about the lamp. You defeated the interlock for a test, so my next gu ess if a lamp doesn't fix it is an intermittent speed sensor on the color w heel. If the sensor doesn't report rotation or is gimpy enough to prevent phase lock, the TV will shut down. Unfortunately, Samsungs of this era hav e no error codes to access.

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Rick 11 years ago

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

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HDTV turns off

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