WOT: Rear projection tv help, Mitsubishi 50" Options

[Sparky]

I've got this older 50" Mitsu that is suddenly acting up. When powered up the display hourglasses then it powers down after about 2-3minutes. Then will not power up again until cold. I think I've narrowed it down to either crt coolant leaking from the green crt causing some arcing in the yoke or something in the primary geometry circuit. Anyone know how to remove the crt's in a Mitsu? I think I can reseal it and re-shellac the yoke. I don't feel like spending the cash to replace the tv and the service company I called blew me off today.

Thanks!
Mike D.

[Verruckt]

I have the same exact old tv. If you check out on the web, there is apparently a solder connection that cracks from heat over time. It's a fairly cheap fix. Just call your local tv guys, they will know all about it. It's a common thing with these older Mitsubishis i guess. (IMG:http://www.914world.com/bbs2/html/emoticons/unsure.gif)

[TonyAKAVW]

Sounds a lot like a cold solder joint to me or some copmonent going bad that is heat related.


About a year ago I found this big RP crt TV sitting on the sidewalk in front of someone's house. I knocked on their door and asked if it was junk. They said something about the image becoming narrow and thought it was a bad CRT. They figured it was a few hundred bucks to have it fixed, so it was up for grabs.

I took it home and figured it was something in the horizontal sweep control. I bought the service manual for the TV for $35 and that included the full schematics. I traced it down to a cold solder joint on a three terminal voltage regulator which I reflowed.

There's a great forum for TV repair and I suggest you pose your question there. There seem to be a lot of techs on there who know a lot about these things..

http://www.network54.com/Forum/185128


If you do a search for your make and model of TV I'm sure you can find a place that will sell you one cheap.


-Tony

edit: I'm sure you are already aware of this based on what you had in your post... but I'll say it anyway....
beware of the high voltages in these things. The capacitors in the power supplies store a gigantic charge and at high voltage. Chances are they have bleeder resistors but always treat them as if they don't. the power supplies in these can easily exceed 30kV and a lethal.

[Rider914]

Check your caps - Get some freeze spray and chill each capacitor when in fail mode. I think you will find a few that are bad.

[Jeffs9146]

[QUOTE]there is apparently a solder connection that cracks from heat over time. It's a fairly cheap fix.[QUOTE]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)

I had a sony that did something like that once! The repair guy wanted $700 plus labor to fix it so I opened it up and figured I couldn't make it worse! I flowed all of the joints that looked old or funny and put it back together!!

It still works 5 years later!!

Good Luck! You have nothing to loose by trying it yourself!

Jeff

[bd1308]

caps are the biggest killer with computer motherboards too---most of the time if you find your system locking up randomly, it's the caps....

my dad had a motherboard that all of a sudden died, and every cap on the voltage control side of the motherboard was blown..

[914GT]

Hopefully it's not a shorted winding in the yoke. That would hose the geometry then eventually overheat and shut down due to the abnormally high currents. As mentioned above, electrolytic caps often do cause problems especially with DC supply circuits. A close inspection sometimes shows the tops of the cans bulging when they've gone bad. The result is a lot of ripple/noise on whatever voltage they are supposed to filter.

[Rand]

Install a Pertronix. And check the longs for rust.
(IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif)

Oh man Britt, you scare me. Messing with caps on a computer mother board? Careful, you may end up with a spark plug (er, I mean DIMM) melting or something.
(IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

If it's out of warranty, touching up the solder joints (just re-melting is usually enough) is safe if you're careful, and sounds like it just may be the fix on this.

[bd1308]

scared? Ha, I laugh in the face of danger

--Simba, The Lion King


I may nil to nothing about 914s, but I've building computers for a LONG time....

which reminds me, Matt how's your computer coming?