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bjorn_and
September 30th, 2012, 02:16 PM
Hi!

I just got myself an XT-286 with a 5154 monitor. The computer is in almost mint condition, however the monitor is not OK. The image, no matter what video mode, gets compressed and distorted to about the upper one fourth of the display as in the image below (I have tried connecting it to a CGA card, tried different EGA modes etc., same result always.):

10424

I ran the EGA card on a 5153 monitor (after changing DIP-switches) and the card seem to work perfectly OK just to rule that out.

I've been googling and searching this forum, but haven't found a satisfactory solution to the problem. I know a guy who used to repair TV's so my plan is to send it to him, but it would be good to give home some clues for where to start looking. (Actually, I found one poster who had the same problem, but he never got a reply to his post as far as I could see.)

Also, is there anyone who has access to the schematics of this monitor or knows where I can find it? I'm pretty sure it will be needed if I'm going to send it away for repair.

Thanks!
Björn

Stone
September 30th, 2012, 03:00 PM
Just a wild guess but a bad capacitor or two might be the source.

bjorn_and
September 30th, 2012, 09:05 PM
Yes, very probable, but I opened it up and took a look and there were no visual clues of any bad capacitors. They can of course be bad without showing signs of leakage.

I was hoping someone had a more specific idea since it feels the symptoms are rather specific. I'm not sure if what I'm experiencing is what is called "vertical folding"?

There seems to be an IC, TDA 2653 A, which can cause that problem if it breaks. By luck, I found one of those at an electronics part store right where I live. They had only one left and it was just $2 so I bought it just in case that's the problem.

Thanks!
Björn


Just a wild guess but a bad capacitor or two might be the source.

patscc
September 30th, 2012, 09:31 PM
It's a pretty safe bet it's in the vertical section. Take heart, at least you've got horizontal, and even HSync and VSync. For reference, what is it we're looking at on the monitor ?
What do you have in the way of test equipment ?
patscc

bjorn_and
September 30th, 2012, 10:33 PM
Hi!

We're looking at about ten rows of text (output from autoexec.bat). However, even if the screen was filled with 25 lines, it would still fill the same area. The below screen shows Alley Cat (CGA game, but EGA looks the same, video mode doesn't seem to matter at all).

10427

I don't have any test equipment for testing the monitor (oscilloscope etc.) and I'm a bit afraid of working with it due to the high voltages so close by. I rather leave it to someone else, but I was hoping to give this guy I know (or rather my father does) a starting point if someone recognized this particular problem. He's been retired for a while and will probably do it fairly cheap so I want to help him out as much as possible. And since he hasn't been working much with modern equipment (not sure if this counts as modern though), I'm not even sure he can do it at all.

Schematics would be very useful, but I think I've learned that the 5175 (PGA) monitor is virtually the same, and I found some fussy scans of that one. Do you think it will work, or are there actual 5154 schematics available somewhere (or better scans of the 5175)?

I'm not afraid of doing some basic trouble shooting and replacing components but I feel this is far from my expertise.

Thanks!


It's a pretty safe bet it's in the vertical section. Take heart, at least you've got horizontal, and even HSync and VSync. For reference, what is it we're looking at on the monitor ?
What do you have in the way of test equipment ?
patscc

modem7
September 30th, 2012, 11:49 PM
Schematics would be very useful, but I think I've learned that the 5175 (PGA) monitor is virtually the same, and I found some fussy scans of that one. Do you think it will work, or are there actual 5154 schematics available somewhere (or better scans of the 5175)?
The 5154 circuit diagram is known to be in the SAMS Photofact for the 5154.
SAMS still sell that Photofact.
https://www.samswebsite.com/en/photofact/search?s=Search&t=model&o=0&k=5154001&submit=Search

bjorn_and
September 30th, 2012, 11:57 PM
Excellent, thank you very much!

A bit expensive, but if I can't find it for free I'll buy it.

/Björn


The 5154 circuit diagram is known to be in the SAMS Photofact for the 5154.
SAMS still sell that Photofact.
https://www.samswebsite.com/en/photofact/search?s=Search&t=model&o=0&k=5154001&submit=Search

modem7
October 1st, 2012, 12:22 AM
I'm not sure if what I'm experiencing is what is called "vertical folding"?
If what you see is a complete image, but simply reduced in height, then that is partial vertical collapse.
If the vertical collapse is such that there is only a line present, then that would be described as full vertical collapse.
If instead, part of the screen image vertically 'folds back' over itself (overlapping), then that is vertical foldover.


There seems to be an IC, TDA 2653 A, which can cause that problem if it breaks.

I'm not afraid of doing some basic trouble shooting and replacing components but I feel this is far from my expertise.
In my experience, failure of the TDA2653 was the commonest cause of vertical related problems in the 5154.
You could take a chance by simply replacing the TDA2653 now.
If that doesn't fix the problem, you will have lost $2, and quickly ruled out the probable cause of the problem.

bjorn_and
October 1st, 2012, 12:43 AM
OK, then I guess it's a vertical collapse, but I need to look closer. It could be that it folds over on the top, I will look more carefully when I get home.

I don't even know where that IC sits and I haven't got the new one delivered yet but do you think I can replace it without taking the risk of electrocuting myself? (obviously those voltages are not in that area, but if there's little space around it's easy to touch stuff you shouldn't I guess)

The help I get here is great btw :)

Thanks!
Björn


If what you see is a complete image, but simply reduced in height, then that is partial vertical collapse.
If the vertical collapse is such that there is only a line present, then that would be described as full vertical collapse.
If instead, part of the screen image vertically 'folds back' over itself (overlapping), then that is vertical foldover.



In my experience, failure of the TDA2653 was the commonest cause of vertical related problems in the 5154.
You could take a chance by simply replacing the TDA2653 now.
If that doesn't fix the problem, you will have lost $2, and quickly ruled out the probable cause of the problem.

modem7
October 1st, 2012, 01:35 AM
OK, then I guess it's a vertical collapse, but I need to look closer. It could be that it folds over on the top, I will look more carefully when I get home.
Which one is not important.


I don't even know where that IC sits and I haven't got the new one delivered yet but do you think I can replace it without taking the risk of electrocuting myself? (obviously those voltages are not in that area, but if there's little space around it's easy to touch stuff you shouldn't I guess)
Okay. So you are entertaining the idea of doing the replacement yourself.

From memory, you are going to have to dismantle most of the monitor, in order to remove the main circuit board (which has the TDA2653 on it).

Have a read of pages 2 to 5 of the document at http://www.crtsolutions.com/CRTSafety.pdf

So, throughout the procedure, be careful that you do not break the glass neck of the CRT. Play safe by wearing safety glasses.

Remove the power cord from the 5154 a few hours before opening it. Certainly after a few hours, capacitors in the power supply and on the various boards will have discharged. That leaves one big capacitor, the CRT, which holds the 25,000 volts. The proper procedure is to discharge the CRT's anode (even after a few hours) per what is shown in the document I pointed to earlier.

The overall dismantle procedure should be:

1. Remove the power cord from the 5154.
2. Wait a few hours.
3. Open case of 5154.
4. Discharge the CRT's anode, then remove the anode cap from the CRT.
5. Very carefully remove the CRT board from the end of the CRT. Slightly wiggling the board as you pull it off helps.
6. Remove power supply unit (big metal cage).
7. Remove video driver unit (other big metal cage).
8. Remove main circuit board. You will find that some plugs will need to pulled off the board.

The above is possibly reflected in the SAMS Photofact for the 5154.

bjorn_and
October 1st, 2012, 01:56 AM
Very good walk-through, but it sounds a bit too dangerous, I always get a bit nervous around high voltages. I think I'd rather leave it to an expert.

But thank you anyway, the disassembly part could perhaps be useful for the one doing the work!

Btw. there's the TDA2653 and the TDA2653 A. I ordered the "A" version as it seemed to be the one I should be using from other posts, but you refer to TDA2653. Is that the one I should try to find? They seem to differ in packaging at least.

/Björn

Which one is not important.


Okay. So you are entertaining the idea of doing the replacement yourself.

From memory, you are going to have to dismantle most of the monitor, in order to remove the main circuit board (which has the TDA2653 on it).

Have a read of pages 2 to 5 of the document at http://www.crtsolutions.com/CRTSafety.pdf

So, throughout the procedure, be careful that you do not break the glass neck of the CRT. Play safe by wearing safety glasses.

Remove the power cord from the 5154 a few hours before opening it. Certainly after a few hours, capacitors in the power supply and on the various boards will have discharged. That leaves one big capacitor, the CRT, which holds the 25,000 volts. The proper procedure is to discharge the CRT's anode (even after a few hours) per what is shown in the document I pointed to earlier.

The overall dismantle procedure should be:

1. Remove the power cord from the 5154.
2. Wait a few hours.
3. Open case of 5154.
4. Discharge the CRT's anode, then remove the anode cap from the CRT.
5. Very carefully remove the CRT board from the end of the CRT. Slightly wiggling the board as you pull it off helps.
6. Remove power supply unit (big metal cage).
7. Remove video driver unit (other big metal cage).
8. Remove main circuit board. You will find that some plugs will need to pulled off the board.

The above is possibly reflected in the SAMS Photofact for the 5154.

modem7
October 1st, 2012, 02:03 AM
Btw. there's the TDA2653 and the TDA2653 A. I ordered the "A" version as it seemed to be the one I should be using from other posts, but you refer to TDA2653. Is that the one I should try to find? They seem to differ in packaging at least.
My notes indicate TDA2653A.

bjorn_and
October 1st, 2012, 02:11 AM
Thanks!


My notes indicate TDA2653A.

bjorn_and
November 30th, 2013, 12:27 AM
Just wanted to follow up on this one.

Replacing the TDA2653A didn't help, neither did replacing the most suspicious capacitors according to some information I got from various sources. But Replacing all electrolytic capacitors did and now it's fine.

Instead of trying to find out what the problem is, it seems as if the most time and cost efficient thing to do would have been to just do that operation from start. Those capacitors are time bombs anyways. I think that was more or less the first advice I got in this thread.

It would need some color adjustments though, but I can live with that for a while. It's not that bad and I have another 5154 I also got fixed which is almost perfect now.

Björn


Thanks!

modem7
November 30th, 2013, 01:38 AM
Replacing the TDA2653A didn't help, neither did replacing the most suspicious capacitors according to some information I got from various sources. But Replacing all electrolytic capacitors did and now it's fine.

Instead of trying to find out what the problem is, it seems as if the most time and cost efficient thing to do would have been to just do that operation from start. Those capacitors are time bombs anyways. I think that was more or less the first advice I got in this thread.
It can 'luck of the draw'. The post [here (http://www.vintage-computer.com/vcforum/showthread.php?9462-IBM-5154-Troubleshooting&p=84342#post84342)] is a forum member indicating that his 5154 issue was fixed by replacement of the TDA2653A. Good to hear that another 5154 was 'saved'.

bjorn_and
November 30th, 2013, 02:16 PM
Thanks! I guess I'm lucky to now possess two of those in working condition :)

I've read the thread you mention and pretty much anything I could find about broken 5154's.

Replacing that chip was a good advice, but looking back I think the most time efficient thing would have been to not only replace that chip but also all those capacitors at once.

The first guy I gave it to had the monitor for very long, trying to fix it in his spare time. He gave up after a while, I guess he didn't have enough of it (time).

The second one hade a week available between jobs. He spent a few hours actually trying to find the issue but when he didn't succeed doing so in those hours he came to the conclusion that instead of searching and measuring everywhere trying to track down the issue as he was short of time, he figured those capacitors, more than 25 years old and probably not meant to last more than 10, would give up anyway soon so he just replaced them all hoping it would help.

I don't know exactly how long time that took, but it was fairly quick, about two hours. The total cost for parts was about $70.

Having read all the forum threads, repair tips etc. around the web, the problem seem to most often be with a broken cap or the TDA2653 so you might as we'll just replace them all, it's not that many, and save yourself some time. Eventually you will probably have to do it anyways and in the end your monitor is as good as new (if the tube itself is OK!)

If you think it's more fun doing it the "proper" way or have more time than money, then that's probably the better way to do it.

I think $70 was cheap and if I had to pay someone full price for the time spent on it I think what in the end was done would be the fastest option.

I could have done it myself of course but I have a deep respect for those CRT's and I was also afraid of breaking something. I'd rather have experienced people doing this, instead of me likely break the neck of the tube or get electrocuted. Or both.

Björn

Stone
November 30th, 2013, 02:52 PM
I'd rather have experienced people doing this, instead of me likely break the neck of the tube or get electrocuted.Hey, Björn, breaking the neck of the tube is no big deal... but getting electrocuted IS! :-) :-) :-)