TV Screen Shrinking Vertically to 1 line

[tesco]

Something's been up with my TV for a while now but it's getting worse and worse to almost unusable.:cry:

What was originally happening is that the TV screen starts to pull up at the bottom showing just a black border at the bottom, and having shrunken picture between the point it went up to and the center of the screen (hard to explain really without seeing it do it).
- Hitting the tv a few times would fix this usually
- It could come back once in a while while watching or not do it at all some times
- It doesn't happen once the TV has been one for a while which might mean it's something to do with heat


Now what's happening which is even worse is that after the tv has been on for about 5 the entire screen will randomly shrink to just 1 line. Sometimes hitting the tv will fix it, today i've had no luck with that and am stuck with the 1 line after the tv has 'warmed up' for 2 mins. :cry:

I searched google and found this:

I don't have a diagram on this set, but from the symptom that you describe, you have a problem in the "vertical circuit". This circuit is what spreads the picture from top to bottom. Usually the first thing that fails, are the vertical filter capacitors. They will cause the picture to pull down at the top, up from the bottom, or both. They will also cause the vertical ic to over heat and possibly short. If it shorts, you will have a line across the screen.
I don't really understand it though...does anyone think I could repair this?:unsure:

Pic:
2038

[Seedler]

Get a new LCD HDTV.:)

[tesco]

I found some instructions for atleast removing the vertical circuit/coil/whatever it is but involves dicharging the crt/caps.
How is that done? I don't really think i'd be up to that task, but depends what the steps are. :P

[Virtualbody1234]

That involves high voltage. Not recommended for most home users.

Be very careful if you decide to proceed further.



Also check to see if your TV has a 'Service mode' switch. If its contacts are dirty you could have the symptoms you describe.

[zaphodiv]

The fact that hitting it may may it work suggests there is a reasonable chance it is a dry joint on the circuit board. If you can get it sufficiently apart to get at the bottom of the board without wreaking it or breaking the tube and seriously injuring yourself then going over any dodgy looking joint with a soldering iron may fix it.

If it's twenty years old and the board has brown flux on it a can of coldklene or some methalated spirits may be usefull.

There is usually an encapsulated black thing on the main board with a think red wire going to a terminal under a rubber cover on the tube that has a zillion volts on it. I recommend not touching it and leaving the set unplugged for a few hours before you open it up. I'v read that the proper way to discharge it is with a wand with an insulated handle and a tip connected to ground through a few megaohms of resistance. If it's fully charged you can get a spark a couple of inchs long off that terminal so putting your fingers near it is not a good idea.

I have some permanent scars from being careless with high voltages.

New TV's are so cheap that you can't make money repairing TV's these days so I havn't done much with them.

[TheDave]

:dabs:

just turn your TV on when it's unplugged, then leave it a few hours just to be safe

[tesco]

The dry/cold joint is what I thought too.
I read up on how to discharge it and don't really feel safe doing that so I thinkk i'll just put up with this until I get a new tv. :(

[harrycary]

You won't be able to fix this yourself. If it's less then 10 years old, take it to a shop for repair. It shouldn't be more than $100US unless there is major component failure.

Since the symptom changes when rapping the side of the set the likelyhood of failed cold soldered joints is probably it.

While repairing bad soldered connections is fairly easy, finding them is the hard part. They don't always appear to be bad and use of a meter is often required.

So, since there are literally hundreds of them, good luck with that.

And, this doesn't address the safety issue. The CRT can stay charged with thousands of volts well after you've unplugged it.

my .02¢. [and 7 years in the repair business] worth.

[Chewie]

Years ago a neighbour of mine needed to discharge a CRT.
In the stairwell of the block of flats we were living in, I watched, transfixed, as he tied one end of a piece of wire to a metal railing and the other to a large screwdriver, then eased the screwdriver under the cap on the CRT.
He's now a pretty successful systems developer, despite what looked like a death wish.

[tesco]

Years ago a neighbour of mine needed to discharge a CRT.
In the stairwell of the block of flats we were living in, I watched, transfixed, as he tied one end of a piece of wire to a metal railing and the other to a large screwdriver, then eased the screwdriver under the cap on the CRT.
He's now a pretty successful systems developer, despite what looked like a death wish.
Why would he do it to the railing.:blink:

[lynx]

Years ago a neighbour of mine needed to discharge a CRT.
In the stairwell of the block of flats we were living in, I watched, transfixed, as he tied one end of a piece of wire to a metal railing and the other to a large screwdriver, then eased the screwdriver under the cap on the CRT.
He's now a pretty successful systems developer, despite what looked like a death wish.
Why would he do it to the railing.:blink:So he wouldn't fall down the stairs when he got a shock from the CRT. :rolleyes:

[Chewie]

Years ago a neighbour of mine needed to discharge a CRT.
In the stairwell of the block of flats we were living in, I watched, transfixed, as he tied one end of a piece of wire to a metal railing and the other to a large screwdriver, then eased the screwdriver under the cap on the CRT.
He's now a pretty successful systems developer, despite what looked like a death wish.
Why would he do it to the railing.:blink:
To discharge the CRT through them, via the screwdriver and (electrical) wire.