Is 32" Too Big?

[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.

[Zenith26kc20]

I agree with the 27 inch replies. The tubes are rugged and the sets (except the late model Zeniths and silver gray cased RCA's) last a long time. I have an ancient Sharp 25 inch that plays great yet!

[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).