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IBM XT display (IBM 5151/5151002) How to open?

MBaNL

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Joined
Aug 20, 2011
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40
I just picked up a IBM XT along with the monitor that is sold as "dead". If I plug the power in it is complete silence (I expect a high tone from a CRT).

I already have all the screws out of the bottom but there are two "things" at the top I can't get off... It's so fragile I first want to here from an expert what to do in my quest of "opening the 5151".
 

Maverick1978

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Mar 29, 2010
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I've never opened one up, so can't help you with that, but if you need schematics, you can find them here.

Don't expect much on the site yet (I dont even have the page built to access those schematics yet), but it's slowly coming along...
 
Last edited:

per

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Jan 21, 2008
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The 5151 doesn't generate sync by itself, so you will have to run it connected to a MDA or compatible video card to test the picture.

Aside from that, the 5151 is one of the simplest monitor designed for PC usage. It practically consists of four sections: The powersupply, the video signal processing section, the sync signal processing section, and the CRT driver with the CRT itself. The processing sections are mostly just amplifiers used to mix the video signals and prepare the signals for the CRT driver cirquit.

You can open the monitor by unscrewing the two screws facing forwards at the base of the monitor, and the two hidden screws under the plastic plugs on top of the monitor. I used a small flat-headed screwdrive for removing the plastic plugs, which shouldn't be too hard; they're not that fragile.
 

MBaNL

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Aug 20, 2011
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@per, So I should more think in the way of a dead videocard?

What does a 5151 when you power it with a external cable? (so no video connection at all) Will the screen go on and be green?
 

nestor

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What does a 5151 when you power it with a external cable? (so no video connection at all) Will the screen go on and be green?

With power connected and no video cable connected, the IBM 5151 does not power up
 

MBaNL

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Aug 20, 2011
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Just found out that the power supply is the main (hopefully the only) problem with my XT... The last owner as well I thought the machine was O.K. because it makes sound. After I opened the case it was only the power supply fan that was spinning and trough the "fan-grille" (I hope that's the correct translation) I saw it was a 230V fan...

I will try to take the power supply apart and hope for a quick diagnose... Is it a know problem with the IBM XT power supply?
 

Great Hierophant

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Mar 22, 2006
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If you connect the monitor directly to the power outlet or strip, it will seem as if it is off. It will "turn on" when it receives a video signal and work fine.

There are two tabs on top of the 5151 case. These need to be removed in order for you to get at the screws. You will probably break them by doing so.
 

MBaNL

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Joined
Aug 20, 2011
Messages
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@modem7, I actually have a XT type power supply and just tested it and the XT starts up and is working perfectly! Only problem is that the power supply I fitted at the moment is from a old big-tower server thing and is to high for the XT.

I visually inspected the original power supply and could'nt find anything... I hope I can trace the problem (the fuse is O.K.) but I'm thinking about breaking down the power supply and fitting another one inside of it. I hate to step away from it's originality but for now it's the only way the bring life back in the XT.
 

modem7

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May 29, 2006
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A common repair technique used on switch mode power supplies that have no visible faulty component/s, is to replace the aluminium electrolytic capacitors in batches.

A friend and I have encountered moisture getting into glass-encapsulated switching diodes. That was where it was obvious that the computer had been stored in moist conditions, e.g. back yard shed.

Just in case you are unaware, the large capacitors in the power supply can hold significant charge well after the power supply is disconnected from the mains.
 

MBaNL

Member
Joined
Aug 20, 2011
Messages
40
@modem7, I know the facts about elco's... my study was about electronics.
About the way it was stored... I have no information on that but since the state of the housing is in very good condition (only dirty but not rusty) I don't think it was stored in moist conditions.
But I will see what I can do with the power supply, anyway thanks for the tips!
 
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