32" tube TV distortion

My TV is about 11 years old, it's a 32 inch tube Toshiba. It's a model CF32G50, manufacture date, August 1997, and the chassis number is TAC

9715.

The distortion is sort of like half circles on both sides of the screen, with "rays" that "flutter". The middle of the screen is brighter, but can only really see that if I have a solid light color background, such as a webpage displayed, or a menu for the DVD player.

I could see the pattern at times even when watching regular TV when I first bought it. I called repair out twice after purchase and they couldn't find anything "off", so I had this problem the whole time I had the TV.

Now that I'm using the TV also to display my computer, it's really bringing the defect out, especially on static screens where one color dominates. Very irritating. Not absolutely sure, but I think my TV may have an automatic degausser built in. The TV has never been dropped or damaged, and I've had the TV in about 5 different houses now.

I linked a crude drawing as it's about impossible to take a decent picture of a TV screen, link below.

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Any info helpful if it's something that can be taken care of reasonably easy. Thanks much.

Reply to
dke3591
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This is probably a CRT problem, caused by shipping damage.

My first Toshiba CZ 3299K suffered from really weird distortions, not unlike yours. A reviewer had similar problems with his sample of this set. Toshiba took my set back and refunded the purchase price, but the unit was bisected by a fork lift at Toshiba, and no one ever figured out what the problem was.

I hope someone here has the right answer. If not, put the set in the back of a pickup truck and run it over rough roads. (Seriously.) It couldn't hurt!

Reply to
William Sommerwerck

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Its really hard to tell much from your sketch, but I'd check the degauss posistor - sometimes the internal thermistor pellets crack or shatter causing all kinds of mischief.

The most common type has 2 elements, both PTC thermistors, one is in series with the degauss coil so as it self heats and increases resistance the AC current through the coil decays. The other NTC pellet is directly across the switched AC so it additionally heats the degauss pellet effectively switching it off.

There is another rarer 3 pin type - one of the pellets is NTC and is in series with the AC feed to the bridge rectifier.

Some modern TVs have a similar degauss posistor to monitors - a 2 pin single element PTC controlled by a relay.

Reply to
ian field

You forgot to plagiarise the "face down on a pile of blankets" bit!

Reply to
ian field

Could this guy be describing a moire pattermn?

Bob Hofmann

Reply to
hrhofmann

Could this guy be describing a moire pattermn?

Bob Hofmann

That was my thought, Bob. In which case, it's effect may be able to be mitigated by a very slight tweak of the focus control - literally no more than a couple of degrees of rotation.

Arfa

Reply to
Arfa Daily

Hi, thanks all for replying. It does in a way resemble a moire pattern, but they are like "rays" coming out of those "half-circles", something like a moire, but not exactly the same in my opinion. The pattern seems broken (normal) between the rays, but the rays seem to "wave". However the pattern kind of disturbs the affected areas similar to a moire pattern with a similar shade of obstruction, on a white screen, the screen looks a little grayer under the patterns.

I don't see a focus control on the remote, is it a hidden control, as I want to try that. Thanks.

Reply to
dke3591

Hi, thanks all for replying. It does in a way resemble a moire pattern, but they are like "rays" coming out of those "half-circles", something like a moire, but not exactly the same in my opinion. The pattern seems broken (normal) between the rays, but the rays seem to "wave". However the pattern kind of disturbs the affected areas similar to a moire pattern with a similar shade of obstruction, on a white screen, the screen looks a little grayer under the patterns.

I don't see a focus control on the remote, is it a hidden control, as I want to try that. Thanks.

It will be located on the back of the flyback transformer. This is the (usually) black cylindrical plastic piece that the thick high voltage wire from the CRT bowl goes back to. It is usually located at the back right corner of the chassis as you look into the back. There will normally be two plastic knobs with screwdriver slots, sticking out of one vertical face of the transformer. Often, these will face out towards the back, but sometimes, they face towards the right. One of these controls will normally be 'sealed' with a paint like nail polish, and the word "screen" (or "A1") will be embossed in the plastic by it. DO NOT adjust this one, as it has a profound effect on the operating conditions of the CRT. The other knob should be marked "Focus". You can twiddle that one to your heart's content.

One last thing. Be careful what you are touching in the back, if you are not experienced in this sort of thing. There are some very nasty sources of lightning in there, and they *will* bite you if you provoke them ! Good luck with it. Hope you get somewhere.

PS. Ian's suggestion about the degaussing positor is also a good one. I seem to remember back in the dim distant past, having a similar problem that turned out to be that the degaussing circuit was continuously *very slightly* running due to a faulty posistor. You would need a service shop to sort that one for you, though.

Arfa

Reply to
Arfa Daily

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