EGA Monitor repair

Discussion about old graphics cards, monitors and video related things.

EGA Monitor repair

Postby Predator99 » 2017-12-09 @ 15:02

Dear all,

I am happy to still own the Monitor of my very first Computer. Its a Thomson 4570 EGA Monitor from around 1987.
I also have its Manual and the wiring diagrams.

After a storage period of more than 10 years I tried to power it on again about one year ago. First it displayed a good picture. After about 20 seconds a buzzing sound occured and lot of dust came out of the Monitor. I took a picture of it. I turned of the power (and as far as I remember the picture was still there while doing so...). The room smelled for several days.
IMG-20170101-WA0004-r.jpg


I opened the monitor but found nothing suspicious. Then I brought it back in the storage room.

Now I like to get it running again. I dont know anything about monitors and I am quite afraid because of the high voltages. I think its very different from repairing a Computer.

My idea would be to remove the cover, power it on (outside...) and see where the smoke comes from.

Good idea? Or am I going to damage even more?

In the red glue around the CRT there are several cracks. Is this a critical issue or is it OK?

I think its difficult to find a local dealer who is able to repair an EGA monitor...I think its differnt from a TV.

Hope somebody can give me some advice? Any idea where the smoke could come from?

Thanks! :cool:
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DSC_0075_3.JPG

DSC_0060_3.JPG

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Re: EGA Monitor repair

Postby keropi » 2017-12-09 @ 15:25

A capacitor that died can produce both smoke and smell - check for anything burned out - usual suspects are in the PSU area, look at the polypropylene caps as these are always certain to fail after all these years. Maybe it's even a resistor, diode or some transistor - you really need to check for burn damage and take it from there.
My Hyundai EGA monitor also did almost the same thing: powered up and then smell+smoke - it was a polypropylene cap on the PSU that exploded but it was just a filtering cap and the monitor worked OK even without it (I did replace it the next day)
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Re: EGA Monitor repair

Postby Imperious » 2017-12-10 @ 03:59

That part You are talking about with the crack in it is the deflection coil (coils) and that will have absolutely nothing to do with the problem at all.
If You can remember what the smell was like it could help. For instance a sweet kind of smell usually means the Flyback transformer has died.
The big green part is the flyback and if that is the problem then You may as well check the monitor in the Bin, as parts would be almost impossible to
source nowdays.
Other types of smells could indicate capacitor or resistor blown, and in that case You should be able to see a blown part somewhere on the main board.
The fact that You said a lot of dust came out indicates a flyback problem, unless it was smoke, which indicates capacitor or resistor.

Be careful with this if You turn it on as there could be up to 25000 volts in the crt, but if the flyback is dead then likely zero volts.
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-10 @ 16:07

Thanks both for your hints! I inspected the boards, but I noticed nothing unusual. Expected to see some dark traces on a larger area. But I didnt dare to disassemble all boards for inspection.

Smell..it was not sweet. Also not like burnt plastic. More like burnt electronic, dont know how to describe it.
Dust..smoke..you can see it on the 1st photo.

Keropis explanation seems to apply for my monitor as well. As said, I remember it was still working after that explosion.

I will open that monitor again when I have more time, maybe around xmas. I will then post more photos and hope you can support me in case I dont find anything...thanks! :cool:
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Re: EGA Monitor repair

Postby keropi » 2017-12-10 @ 16:23

Have a more detailed look at the psu area/board then - you won't see anything burned if an old polyester cap exploded - you will find it's pieces scattered and half of it soldered LOL
Just replace with a new cap and call it a day - if the monitor still works then most likely the cap was a filtering one.
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Re: EGA Monitor repair

Postby CkRtech » 2017-12-12 @ 22:29

Hey Predator99 - Keep us updated on your progress on this when you pick the project back up. Nice to see monitor work on vogons.
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-26 @ 10:10

Hello again,

made some progress :cool:

I first spotted this area with a blackened resistor. It covered entirely with glue...difficult to do anything here:
IMG_0035r.jpg


Then I removed the controller board and spotted this one here...!
IMG_0051r.jpg

Indeed, that must me the cause of the smoke. Seems to be the same problem as this one
https://www.radiomuseum.org/forum/telefunken_palcolor_3300_defekte_stoerschutzkondensatoren.html?language_id=5

But before I can continue I need to remove that board. There are 2 connectors I am little afraid of touching...:

a) This one is at the top of the tube which looks quite fragile. Any precautions to take before handling this..?
IMG_0063r.jpg


b) This one is on the tube itself:
IMG_0046r.jpg

How is this called? Is there any video explaining how to detach this? But for this one, maybe the cable is long enough to keep it connected...

Thanks for all advice! :cool:
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Re: EGA Monitor repair

Postby derSammler » 2017-12-26 @ 10:23

Any precautions to take before handling this..?

Yes, that's the anode and actually the place where the high voltage resists. Do not even think about touching it without discharging the tube first. This is very dangerous, especially since this is a monitor from 1987 with no bleeder - meaning the high voltage can stay for weeks or even months.
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-26 @ 10:32

Puh, thanks for telling that..!

Just taken a look, the photos from my 1st post were taken 01/2017. And since then the monitor was in a storage room without connecting it to a power supply.
Still any danger? Thats almost one year ago..?
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-26 @ 11:28

So I decided to desolder without removing the whole board. Just opened the lockers and pushed it forward 1 cm.

I removed both, think these are the correct replacements
https://www.reichelt.de/Funkentstoer-Ko ... -X2%2B100n


DSC_6555r.jpg
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Re: EGA Monitor repair

Postby derSammler » 2017-12-26 @ 13:43

Yes, those seem to fit. (are you from Germany, btw?)

They are not needed for the monitor to work, however. You could also just leave them out.
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Re: EGA Monitor repair

Postby keropi » 2017-12-26 @ 14:16

they are X2 filter caps - they help with power-line noise - you can operate the monitor without them until replacements arrive like derSammler mentions
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-26 @ 14:45

Yes, also Germany ;-)

I will wait until they arrive and close the case...hopefully forever...! No fun for me dealing with a CRT...always scared to damage the monitor or to damage myself ;-)

The monitor has also another issue with the power button. It is in "on" position and does not move anymore. I think the reason is the spring...:

DSC_6556r.jpg

But I decided to leave it as it is:
- I cannot reach the second screw without disassembling the board
- its unlikely I managed to repair it or to find an exact replacement
Works also with an external power switch.
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Re: EGA Monitor repair

Postby Predator99 » 2017-12-28 @ 15:21

S-U-C-C-E-S-S :cool: :cool: :cool: :cool: :cool:

Replacment WIMAs arrived today..installed at once...
DSC_6572.JPG


..and tested :cool:


Seems to be running...will report again in some hours...dont trust this yet ;-)

DSC_6580.JPG
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