Toshiba T5200: White mark on screen

[Neosodium]

As mentioned in another thread, I recently acquired one of my most sought after machines, the Toshiba T5200. I managed to get it working, but on the screen there is a white mark that looks a little bit like a radial crack.

The screen still functions without any problems, but the mark is visible at all times as it shows up when lit by external light sources and also blocks light output from the screen.

I took the screen casing apart today to see if there was a cover over the actual plasma screen and what I found was a very thick bit of glass stuck down on top of it.

I presume this is to make the screen stronger, preventing it from shattering as easily but the white mark is on the underside of this glass.

Is it possible to carefully prise the glass from the screen with a plastic spudger without breaking it, or would it A: cause the screen to shatter or B: cause the neon gas to vent?

 

[arrow_runner]

I can't say specifically for these older plasma LCDs, but with modern laptop LCDs, it actually is possible to take them apart layer by layer and put them back together. While possible, it's extremely difficult to do without damaging something and you'll run into issues with dust getting trapped between panels.

Also, when my first Compaq Portable arrived with the shattered screen, the front glass came off in chunks. From what I recall, it didn't look like that glass piece did anything other than to protect the LCD behind, but I couldn't tell you if it was originally sealed to hold in the gasses.

I don't know if that helps or not. Hopefully someone knows more about how these are designed. Is the glass 100% sealed to the rest of it?

 

[SpidersWeb]

Generally with imperfections like this it's better to ignore it than to fix, at least until you have a backup plan, or you can make things a lot worse.
Personally I'd wait until you have a spare T5200 screen before you do any work.

 

[Neosodium]

I can't say specifically for these older plasma LCDs, but with modern laptop LCDs, it actually is possible to take them apart layer by layer and put them back together. While possible, it's extremely difficult to do without damaging something and you'll run into issues with dust getting trapped between panels.

Also, when my first Compaq Portable arrived with the shattered screen, the front glass came off in chunks. From what I recall, it didn't look like that glass piece did anything other than to protect the LCD behind, but I couldn't tell you if it was originally sealed to hold in the gasses.

I don't know if that helps or not. Hopefully someone knows more about how these are designed. Is the glass 100% sealed to the rest of it?

It's not a kind of LCD - gas plasma displays work entirely differently; they are like a giant neon glow lamp with thousands of glowing electrodes. Sorry to hear about your Compaq Portable - I have one with a dead motherboard here if you're still looking for a replacement screen.

Generally with imperfections like this it's better to ignore it than to fix, at least until you have a backup plan, or you can make things a lot worse.
Personally I'd wait until you have a spare T5200 screen before you do any work.

If I had a spare screen I would just fit the spare screen do you know anywhere I could get hold of a spare? or is it a case of looking out for beyond-repair T5200 systems with an intact screen on ebay because that will take a long time considering how rare the machine is.

 

[Chuck(G)]

My feeling is that the top glass cover of the plasma display is very, very thin--any attempt to remove the protective glass will likely result in grief. About all that I can think of is to heat the top glass very slowly with a hot air gun and see if the adhesive softens up enough to allow the protective glass to be lifted off. I estimate the chances of this working at less than 1 in 10.

 

[MikeS]

Looks like it might be a bit of mold starting to form, a common problem with old CRTs; surprised to see it on a Toshiba plasma screen.

I can't speak for the 5200 but on the 3100 and 3200 the protective glass is held on with double-sided tape; I have very carefully removed and replaced it on my 3100 but YMMV, do at your own risk, etc., and the usual cautions and disclaimers.

 

[SpidersWeb]

If I had a spare screen I would just fit the spare screen do you know anywhere I could get hold of a spare? or is it a case of looking out for beyond-repair T5200 systems with an intact screen on ebay because that will take a long time considering how rare the machine is.

LOL yes

But I was more meaning that it might not be worth taking any risks with the display (your call though).

The motherboard in my T5200 died, by fluke I found a replacement mainboard on ebay, but I suspect other dead ones (*COUuntestedGH*) must show up on ebay occasionally.

 

[RickNel]

Looks like it might be a bit of mold starting to form, a common problem with old CRTs; surprised to see it on a Toshiba plasma screen.

I also thought of mold (but we spell it mould). That would imply that the relevant layers are not airtight - mould needs carbon dioxide and H2O vapour AFAIK. So separating the layers safely might be possible. Most moulds are killed by UV light. The plasma must be emitting some UV, but I don't know how much. So it could be mould that grew in dark storage conditions but was killed when the display was put back into use. You could experiment non-destructively by exposing the spot to a UV source while masking the rest of the surface, and see if there is any color change. UV should bleach it if it is mould, though would not necessarily reduce the opacity. But if proven to be mould, that might encourage an attempt to separate the layers and clean it out.

I know from sad experience that in separating the layers of a laminated display, it's essential to avoid damaging the fragile switching matrix connections that run along at least two sides of the rectangle with flexible plastic printed traces glued to extremely narrow metal contacts. Breaking a single X or Y connection ruins the entire display.

Rick