What's the opposite of pin-cushioning; what causes second problem?

Question 1: On a tv screen, what is the opposite of pin-cushioning called?

Question 2: I have a 12 inch Sony color tv, with turret tuning and a separate UHF turret tuner, with detents. I guess it's about 25 years old.

I've been using it for about 2 months and, mayb surprisingly, the opposite of pin-cushioning (OPC) doesn't bother me. I only notice it rarely, when there are some vertical lines near the edges of the screen, or at the end of a movie when the credits crawl by.

A couple days ago, within a day or less, two vertical lines appeared, about 1.5 inches from the left edge, about a quarter inch from each other, each about 2 or 3 mm. wide, the right one from the top of the screen to the bottom, the left one from the top of the screen 9/10ths of the way to the bottom, sometimes only to 2/3rds. The lines flare out at the top and bottom, I presume because of OPC.

The tv hasn't been dropped or shaken or even lifted at all in the last month.

This isn't a case of the picture folding over. The rest of the picture is fine.

I thought it was dirt on the screen, somehow, but it's inside the glass. It's visible when a tv show is on, when there is no signal to the tv, and not visible when the tv is off.

I don't have much expectation of fixing this, but I would like to know what it is, how it can happen.

Reply to
mm
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Barrel distortion. For the obvious reason... There may be a 'pin amp' or 'pincushion' marked control that you can tweak (but this would be a remove-the-case-back kind of job).

That's usually where 'ghosting' shows up; there's a strong timing signal on analog TV just to the left of the picture, and if you have a delayed ghost of the timing signal, there will be a (usually dark) bar in that position. Ghosting has this symptom ONLY on analog transmissions, though. Is your set on analog cable?

A second possibility is that the 'screen' adjustment is out of whack (this usually lowers the contrast on the full display); if you have a gray-bars test pattern (some DVDs come with such on 'em) it will fail to have a good 'black' until the screen is readjusted. Screen readjust is very commonly required with age, and either an insulated screwdriver into the marked hole, or a remove-the-back-and-tweak adjustment is likely to be available.

Reply to
whit3rd

In the UK, we always called it "barrel distortion"

What we used to call "striations" maybe ? Caused by velocity modulation of the scanning beam, and was often due to the damping resistor across the H - linearity coil either burning out, or running so hot that it crystalised its solder joints. Without this resistor in place and working, the lin coil 'rings' a couple of times after the 'shock' of flyback, and produces a couple of vertical lines similar to what you describe, in about that sort of position.

Arfa

Reply to
Arfa Daily

Thanks. I'll look if I ever take the back off this one.

Well, no it's not on analog cable but it's on analog output from the DVDR with OTA reception. Is one different from the other?

No my Philips DVDR with harddrive has a lot of good features, but it's missing a lot of features also.

I do have a dot generator in the basement, but i'll never get around to this. Like I said, I just wanted to know how it could happen.

Thanks

Reply to
mm

And here to it seems. Now I can tell all my friends I have barrel distortion. They may not care, but I will enjoy saying it. At least to one or two people.

Even when there is oonly two vertical lines? Oh, yeah, that's exactly what you say below.

That sounds right. Ringing, and right after it gets zapped back to the left side.

This is close that it's probably enough to fix it. And I might be able to find the H-linearity coil without buying an expensive set of notes, so maybe if this gets worse, I'll save the tv instead of throwing it away.

Do you want at the proper value for the damping resistor? If it's been running hot, I probably can't tell.

Reply to
mm

Both terms are used in photography. Zoom lenses tend to have one form of distortion at the long end, the other at the short end.

Reply to
William Sommerwerck

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