27" Admiral--Color/Degauss problem

[YamahaFreak]

My 27-inch Admiral set (1990's black, not 1950's wood) has some sort of problem with the colors being off, as if a magnet was placed near the screen. Degaussing the set has no effect; the colors are always in the same places and patterns. I have even tried disconnecting the degauss coil (thick black cable running around the back of the CRT) to no avail. I'm beginning to think I may have a bent shadow mask or something?

Here's a photo of the screen, which here, should be ALL blue:

http://www.wolfness.com/up/files/Funky%20Colors.jpg

[Eric H]

That sure looks like a bent shadow mask.
One other possibility, have you checked the yoke to make sure it hasn't shifted or come loose from the tube?

[radiotvnut]

Yep, bent shadow mask or misaligned yoke. Has the set been dropped during it's lifetime?

[YamahaFreak]

Originally Posted by radiotvnut

Yep, bent shadow mask or misaligned yoke. Has the set been dropped during it's lifetime?

I would not know, as I got it secondhand (trash find)

I imagine a bent shadow mask is terminal, unless I magically find a replacement CRT. Is there any way to tell by looking at the tube if the shadow mask is bent? How can I tell if the yoke has shifted, unless it's always loose in such a case?

[freakaftr8]

See where he green is on the top right? Look at the upper middle where the blue turns to green. It looks as if the shadow mask got damaged and tweaked there and warped out of shape. I'm placing bets that the CRT is done.

How's the plastic trimming? Damaged or distorted in any way?

[YamahaFreak]

Originally Posted by freakaftr8

See where he green is on the top right? Look at the upper middle where the blue turns to green. It looks as if the shadow mask got damaged and tweaked there and warped out of shape. I'm placing bets that the CRT is done.

How's the plastic trimming? Damaged or distorted in any way?

I can't see any visible damage by just looking at that area of the screen. However, the top of the plastic housing right above the area in question is badly scraped and slightly cracked, as if the set was on a shelf and fell forward onto the top of its cabinet, hitting a rough surface like concrete. If this is the case, I'm really surprised the CRT didn't break!

[zenith2134]

Sadly this seems to be very typical case of what happens to a dropped crt monitor.

Without the shadow mask in its proper position and shape, purity (and convergence) will never be correct. this isn't the type of thing that degaussing will improve, as you have experienced. New crt is rarely worth the money. Wonder how it happened anyway.

[YamahaFreak]

Originally Posted by zenith2134

Sadly this seems to be very typical case of what happens to a dropped crt monitor.

Without the shadow mask in its proper position and shape, purity (and convergence) will never be correct. this isn't the type of thing that degaussing will improve, as you have experienced. New crt is rarely worth the money. Wonder how it happened anyway.

As I suspected, it's terminal; no way to repair it aside from replacing the CRT. I suppose it's not all bad, though; it's like having some kind of benign tumor--it'll always be there, but it doesn't really get in the way of life. As for how it happened, it's anyone's guess, though if I had to guess, I'd say it happened during a move, as from the marks, it looks like it fell onto a sidewalk or driveway.

Next up: Either a 19" Mitsubishi that keeps turning itself off, or a 25" Magnavox that has issues with dark scenes.

[radiotvnut]

The only reasonable way to fix this is to find a junk TV with a good CRT. As long as the mounting ears are the same and the yoke will properly fit on the neck, it should work. Over the years, I've replaced many bad CRT's with a tube from a junk set and the tube usually didn't have the same number as the original; but, it still worked. Or, just locate another good TV. If you were here, I'd let you have a nice 27" RCA CTC177 real cheap. There was a time when such a set would have brought at least $100; but, everyone now thinks they must have a flatscreen, which makes '90's era TV's very hard to get rid of.

The ones that really irritate me are the TV's that come in with a cracked chassis. Once I'm done repairing 20 broken traces on the PC board, the set will work; but, I discover that the shadow mask is damaged. I finally got to the point where I won't try to fix a badly cracked PC board unless I have another chassis that I can connect to the CRT to make sure it's good.

More times than not, if a TV is dropped, either the shadow mask will be damaged or the CRT neck will snap off.