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have a bizarre issue on my T3200SX display

soviet9922

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Hello, some days ago i got a T3200SX is in very nice shape and the previous owner seem to have restored it because the bios is swap for a custom one have a 20GB one.
He installed also a sound blaster 16 pnp and have dos running, the system have 9 megs of ram.
The display is a plasma orange one, seem to have no bad lines but there's an issue i never seen before in other computer monitors.

Will try to explain it.

The computer display fine but for example if i run a bright program that uses the full display, the screen will show up ok but slowly in a few seconds the contrast will lower and all intermediate amber tones between black and a darkamber tone will fade. Leaving only a single darkamber and total black. For example in dos EDIT program all highlighted text options in the menus will disappear and only i get the black part of the text and the orange background.

If then i exit the program and go back to the dos prompt then run another program the issue will show up in the same manner will start fine and fade in a few seconds to this.

Maybe someone experienced on this model may know what this could be?.

:confused:
 

Trixter

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It sounds like there's a voltage problem driving the display. Some capacitors might be going bad and should be replaced.

Be very careful with that plasma display -- there is no way to repair them.
 

Shadow Lord

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It sounds like there's a voltage problem driving the display. Some capacitors might be going bad and should be replaced.

Be very careful with that plasma display -- there is no way to repair them.

What he said. Mine has the same issue. For some reason edit seems to be a big culprit. You have a few options:

1. Try and fix the controller
2. Replace the controller
3. Set the video to mono mode in BIOS. You lose access to that portion of memory for moving programs to (using a meme manager) but the programs like edit behave better
4. Use mode.com (e.g. MODE BW80) - although I have found this not to work very well
 

soviet9922

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OK i have dissasembled the whole thing and got the display hooked to the psu the HV leads coming from the screen show 170v DC and according to the service manual this never should be lower than 200v so theres something wrong on the psu for sure.
The other low voltages 5v 12v -12v -5v are ok.
Now it's a shame the service manual only talk about replacing the psu and never about how to fix it, the psu also have several adjustment pots on it.
At least from a visual inspection none of the caps seem to be in bad shape i suppose i will raplace all of them.
 

Shadow Lord

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directly from the psu, measured it having the display connected and not the result is the same.

Well that is good news. PSUs are easier to repair then most other stuff. Out of curiosity does your brightness wheel work well i.e. do you get a large range of dark to brightness?
 

SpidersWeb

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I can't help, but I think the failure of the plasma power supply may be somewhat common.
I had a T3200SX with a dead display, I ended up parting it out because another forum member had one which wouldn't start - so I sent him my PSU - fixed this machine but then his screen didn't work.

Will be keen to find out if you find the fault.
 

Shadow Lord

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I can't help, but I think the failure of the plasma power supply may be somewhat common.
I had a T3200SX with a dead display, I ended up parting it out because another forum member had one which wouldn't start - so I sent him my PSU - fixed this machine but then his screen didn't work.

Will be keen to find out if you find the fault.

SpidersWeb,

Did yoursome have any extra ram? If so do you still have it? I have been looking for 4MB (2 x 2MB) stocks to max mine out. Thanks.
 

soviet9922

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Well that is good news. PSUs are easier to repair then most other stuff. Out of curiosity does your brightness wheel work well i.e. do you get a large range of dark to brightness?

Yes the brightness wheel have a good range, but the brightness never was very high never seen one of this in the past so initially i was like "the display is old and used, or this things never have to much brightness on the start" but now seeing the low HV is on the PSU everything seems to point to the same issue.
 

Shadow Lord

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Yes the brightness wheel have a good range, but the brightness never was very high never seen one of this in the past so initially i was like "the display is old and used, or this things never have to much brightness on the start" but now seeing the low HV is on the PSU everything seems to point to the same issue.

My problem is the other way around. Brightness is pretty good but it really does not get very dim (I will post some pictures later). I have a few of these machines around that I have scavenged parts from to make one great one sans the display issues) and even on the one with the "best" screen the range is still seems limited. I am wondering if this is by design or of the pots is dirty. Unfortunately to get to it is not easy and requires a very complete disassembly.

Was that the only cap that was leaking? It would be interesting to see if a simple cap replacement will fix he issue.
 

Chuck(G)

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Sometimes, the front (or rear or side) panel brightness control is just a vernier (i.e. secondary) control, with the main setting on the monitor PCB. The general idea is to give a reasonable user-adjustable range without allowing the user to be stupid.
 

soviet9922

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ok have replaced all the caps on my psu (i let the big ones in the input they are ok) but the bottom of the psu was soaking wet in electrolyte, I'm not sure how the psu can keep working like this.

But the problem is not fix now i have nice 205v DC on my HV lines to the display but the when i power up the computer everything is bright and dandy good contrast but after a few seconds the problem will show up again.

After having my multimeter connected to the display i can see that the voltage never drops now from the 205v so this is fix but was not the issue.

Using the computer if i disconnect the hv line that power the plasma screen, having the laptop turn on and reconnect i will got some seconds of nice brightness and contrast but then it will lower and the issue show up.

I'm sure that the problem is located on the plasma screen controller board, will try the shotgun approach and start replacing stuff on it to check if i can find the culprit.
 

SpidersWeb

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The controller board is quite large and does have caps on it. It was a long time ago I opened mine, but I remember being surprised (although probably shouldn't have been).

ShadowLord - no spare RAM sorry, they always turn up here with base configurations only, so the two sticks in that T3200SX are my only spares / add-ons.
 

Shadow Lord

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ShadowLord - no spare RAM sorry, they always turn up here with base configurations only, so the two sticks in that T3200SX are my only spares / add-ons.

Sorry, not following you: I thought you were parting out your system. But are you now saying you are keeping the ram incase you get another T3200SX?
 

Shadow Lord

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I'm sure that the problem is located on the plasma screen controller board, will try the shotgun approach and start replacing stuff on it to check if i can find the culprit.

Well again if it is just caps easy fix but if it is more complicated then who knows... Did these plasma screens have a failure rate in the screen itself?
 

soviet9922

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Ok, fully recapped the controller board on the plasma display i was unable to source locally axial capacitors so i used normal ones.

Now good news :D at least for me this fixed the issue straight away, now the display works perfectly.
So if anyone have this issue just a simple recap could get the damn thing working again, also if you already don't have done it recapping the PSU is a must it was also in terrible shape.









 
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