Is 32" Too Big?

[jmetal88]

This is probably an odd question, but since I insist on keeping a 'modern' CRT TV around for daily viewing (and since I can't afford any kind of HDTV at the moment), I've been on a search for a set with a good picture that isn't too hard to move around. The year before last, I made the mistake of purchasing a Sony KV-32FS120 from a local restaurant for $40. It had a great picture, but the yoke had apparently come loose (of course they didn't have cable hooked up, so all I got to see before I took it home was a screen full of static), and I had to reposition it and re-install the spacers to make the picture look acceptable. But I soon gave the TV away, for multiple reasons. First of all, after I had been using it for a while, I started noticing color purity issues. I adjusted the yoke to sort those out, but couldn't get the problem to completely go away. Second, the thing was just way too hard to move!

So, as soon as I got the opportunity, I purchased another TV set that had the same size tube, but was much easier to move: a Toshiba 32A33 for $30. This one I was not able to test at all, as it was located in a house that was being moved out of, and the electricity had already been turned off. Now this one had the yoke solidly in place, but it was still positioned where there was a slight upward bend in all the horizontal lines, and I noticed that it also seemed to have color purity issues. I was unable to free the purity adjustment rings on the neck of the CRT, so I had to leave them alone, but I was able to free the yoke for adjustment, which didn't really help much at all. In fact, I noticed that when I pulled the yoke back, the 'impure' patches of color were actually the 'opposite' colors of what I see when viewing the TV with the yoke in its normal position. I've tried degaussing the set as well, but it only helps temporarily, and it only helps when I use the degaussing coil 'improperly' (meaning, I try to magnetize the corner of the set with the largest color issue rather than trying to demagnetize the entire set). Another interesting thing is that the picture just seems to be a little dim along the left-hand side of the screen.

So it leaves me wondering, is 32" too big to get decent color purity out of a CRT? Or is it something about these particular sets that was just causing issues from age? I'm tempted to try and find a decent late model 27" CRT soon for comparison.

[dieseljeep]

Stick with a 27" or smaller. One reasonally strong person can generally handle them. The Sony's are a little heavier.
I think those super big sows are handled too roughly. If they're bumped hard or dropped, even a short distance, can cause shadow mask damage.

[Reece]

I have a 36" CRT Toshiba bought new fall of '04, still going strong, perfect pic, no problem ever. It is herniasville getting around but three guys can handle it.

[radiotvnut]

My rule is that if a TV is too big for me to easily carry by myself; then, it's too big for my needs. Those big TV's, especially Sony's, are real monsters and I can see how they could easily be damaged.

[jmetal88]

Yeah, we actually cracked the plastic on the Sony just getting it in to my car, unfortunately. The Toshiba is a lot easier to move around, and I can actually lift it by myself, although I cannot carry it more than a few feet without at least one other person helping me. I was told the Toshiba was being carried back and forth to video gaming conventions all the time, so I wouldn't be surprised if there was some internal damage to the tube, although I don't know what symptoms I would have to look for to confirm this.

EDIT: But yeah, I'm thinking I should definitely look for a 27" set, or maybe even a 23" again. I used to use a basic cheap-o 23" set, and while it had terrible picture geometry, it did have absolutely no color purity issues. I disassembled it to mount the CRT in an arcade cabinet I'm slowly building from scratch, though, and I'd rather use a set with component video inputs for my daily watching.

[Celt]

My 27" JVC is as big and as heavy as I care to ever deal with.

[holmesuser01]

I aquired a 32" Sanyo set that the owner could smack with their hand and make it work.

It is a 2003 unit, and is now the largest CRT set I've ever owned.

All I found wrong was some bad soldering. Fixed that, and replaced several suspect capacitors that were discolored, but still working, and the set has worked fine for me almost 2 years. It's got a good sharp image with good color tracking.

The large SONY's used to about kill me trying to move their large-ness around on the bench.

I'll go to a flat screen kicking and screaming all the way. I'm sticking with technology that I can still repair!!

[joemama99]

The issues you mentioned were most likely the result of shadow mask damage caused by the unit being dropped.The size of the 32 inch and up units make it real likely that they will take a tumble eventually.I have found that if you get the set in the position you want and unplug the degausser,you can adjust the purity problems out of the damaged ones by placing permanent magnets around the crt until the problem is corrected.Moving the set will mess it back up,though,as will letting the degausser run.

[rcaman]

i use a 32" sony lcd for my computer monitor. love it. 32 and 36 inch sets can be way to much to handle i agree

[jmetal88]

Originally Posted by joemama99

The issues you mentioned were most likely the result of shadow mask damage caused by the unit being dropped.The size of the 32 inch and up units make it real likely that they will take a tumble eventually.I have found that if you get the set in the position you want and unplug the degausser,you can adjust the purity problems out of the damaged ones by placing permanent magnets around the crt until the problem is corrected.Moving the set will mess it back up,though,as will letting the degausser run.

I thought about unplugging the degausser, actually. It seems like the problems lessen as I let the set run longer, and I thought the degausser (which runs on each power up) might be 'resetting' the problem. But yeah, the specific problems with this set are a blue upper right-hand corner and a dim (maybe yellowish?) patch that runs up the entire left-hand side. Funny thing is, I've recently noticed a 13" TV that I've had for years that has never been dropped developing the same problem in the upper right-hand corner, and I'm not sure what the deal is, there. Of course, it's a really cheap TV, and I'm not sure it has an internal degausser, so maybe it just needs to be worked over with my handheld coil.

[zeno]

Sounds like doming. More common on cheaper tubes & high brightess
& contrast. Cut this out for you. If you want to know everything
about CRT's click the link...........


What is Doming?
The shadow or slot mask inside the CRT is a thin sheet of steel or InVar positioned a half an inch or so behind the phosphor screen. The flatter the screen, the more susceptible it will be to thermal expansion effects: With individual phosphor dots spaced as as little as .13 mm apart (for a .22 mm dot pitch CRT), it doesn't take much inaccuracy in their position to result in a noticeable effect. (See the section: How to Compute Effective Dot Pitch.) As a result, high resolution CRTs tend to be more susceptible to doming problems.
(Portions from: Jac Jamar ([email protected]).)

Doming is a deformation of the shadow mask or its support structure caused by heating and subsequent expansion in bright (high beam current) areas of the picture. This causes a shift in position of the finely spaced holes or slots in the mask. The result will be color purity problems - discoloration and brightness variations. For a .28 mm dot pitch CRT, a change of only .14 mm in the position of a hole or slot can totally shift the display from one of the primary colors to another.

InVar shadow masks can sustain a significantly higher current density than steel shadow masks (by as much as 3:1) without noticeable problems.

Trinitrons are more resistant to local doming effects as long as the wires are under enough tension. However, expansion of the suspension components can still result in doming with an overall bright picture.

The onset and disappearance of color purity problems will generally lag the cause due to the thermal mass of the affected components. For local heating resulting from picture highlights, this will be only a few seconds since the thermal mass of a small area of the mask is not that great. However, for effects having to do with expeansion of the suspension or support structure, it may take up to 30 minutes to reach equilibrium.

The orientation of the TV or monitor with respect to the earth's magnetic field and even whether the CRT was set up for the Northern or Southern hemispheres may affect the resulting color shift. Thus, the picture may tend toward yellow while the monitor is facing one way and blue when rotated 180 degrees on its base (even if degaussed at each position).

Reducing the brightness/contrast or setting the brightness limiter will prevent doming but may result in an unacceptably dark picture.

Shadow mask doming in itself is not something that becomes defective and has to be repaired. It is a characteristic of the CRT assembly. However, shifts in the position of purity adjustments can results in increased sensitivity to slight doming.



http://www.repairfaq.org/sam/crtfaq.htm

73 Zeno

[Robb]

Any CRT TV bigger than 13" is not worth buying, to me anyways !
Once you hurt your back, you cant go back !

[dieseljeep]

Originally Posted by Robb

Any CRT TV bigger than 13" is not worth buying, to me anyways !
Once you hurt your back, you cant go back !

That's my trouble! I pass up very few 13" or smaller sets, unless I have too many of one kind. Such as Funai's or Sylvania's. No more Funai built VCR combo's. Yuck.
I have a few RCA "prison-visions", with the built-in DTV boards. They also receive the digital signals from cable. I found them to be very reliable.

[jmetal88]

Originally Posted by zeno

Sounds like doming. More common on cheaper tubes & high brightess
& contrast. Cut this out for you. If you want to know everything
about CRT's click the link...........


What is Doming?
The shadow or slot mask inside the CRT is a thin sheet of steel or InVar positioned a half an inch or so behind the phosphor screen. The flatter the screen, the more susceptible it will be to thermal expansion effects: With individual phosphor dots spaced as as little as .13 mm apart (for a .22 mm dot pitch CRT), it doesn't take much inaccuracy in their position to result in a noticeable effect. (See the section: How to Compute Effective Dot Pitch.) As a result, high resolution CRTs tend to be more susceptible to doming problems.
(Portions from: Jac Jamar ([email protected]).)

Doming is a deformation of the shadow mask or its support structure caused by heating and subsequent expansion in bright (high beam current) areas of the picture. This causes a shift in position of the finely spaced holes or slots in the mask. The result will be color purity problems - discoloration and brightness variations. For a .28 mm dot pitch CRT, a change of only .14 mm in the position of a hole or slot can totally shift the display from one of the primary colors to another.

InVar shadow masks can sustain a significantly higher current density than steel shadow masks (by as much as 3:1) without noticeable problems.

Trinitrons are more resistant to local doming effects as long as the wires are under enough tension. However, expansion of the suspension components can still result in doming with an overall bright picture.

The onset and disappearance of color purity problems will generally lag the cause due to the thermal mass of the affected components. For local heating resulting from picture highlights, this will be only a few seconds since the thermal mass of a small area of the mask is not that great. However, for effects having to do with expeansion of the suspension or support structure, it may take up to 30 minutes to reach equilibrium.

The orientation of the TV or monitor with respect to the earth's magnetic field and even whether the CRT was set up for the Northern or Southern hemispheres may affect the resulting color shift. Thus, the picture may tend toward yellow while the monitor is facing one way and blue when rotated 180 degrees on its base (even if degaussed at each position).

Reducing the brightness/contrast or setting the brightness limiter will prevent doming but may result in an unacceptably dark picture.

Shadow mask doming in itself is not something that becomes defective and has to be repaired. It is a characteristic of the CRT assembly. However, shifts in the position of purity adjustments can results in increased sensitivity to slight doming.



http://www.repairfaq.org/sam/crtfaq.htm

73 Zeno

Thank you! That sounds EXACTLY like what I'm seeing! I'm going to hit some thrift stores tomorrow (ones I've known to have multiple TVs at once) and see if I can't find a smaller set with a higher quality tube in it. 13" I think is too small, but I could go between 23" and 27", I think (maybe even 19 if the set looks good enough).

[jmetal88]

Alright, I picked up a 24" flat CRT Toshiba at a thrift store today for $25. The colors are great on this set, but it has some geometry problems (I notice these seem to be more noticeable on the flat CRTs than on the curved CRTs). Third set in, and I have to say it seems impossible to get a used set that's still in awesome shape, haha. I think I'll be able to sort out most of the geometry problems with this set by twisting the yoke around, though. In fact, I just twisted it to the left a little and it's already a lot better. Now I think it just needs the spacers adjusted a bit to get rid of some of the bowing of the picture up and down on the outer edges.