PDA

View Full Version : Found an IBM 5151 monitor outside this morning.



digger
April 23rd, 2010, 01:55 PM
This morning, when I left my apartment to go to work, I noticed some computer stuff dumped outside by the trash. The old matrix printer and clone VGA monitor didn't interest me, but the IBM 5151 monitor did!

Unfortunately, a copper scavenger had gotten to the poor thing before I did, and its cables were cut off. The brutes! :( Also, there appeared to be a fairly large nasty crack at the bottom, close to were the cables came out of the case. I'm not sure if the same person who cut off the cables was responsible for that, since there seemed no point in breaking it open there, as you can see in the pictures attached below.

Apart from the damage at the bottom, it seemed in pretty good condition. I haven't made pictures of the front yet, but the screen seemed undamaged when I saw it briefly. At first I hesitated a bit and started walking away, since it was damaged, but then I realized that these things are quite the collectors items these days, and are increasing in value. Besides, I suspect that some of you would never have forgiven me, had I left this potentially valuable find with the trash. So I took it in my arms and stored it in my in-door bike shed, where it's now sitting dry, safe, and behind lock and key.

Of course, now comes the question: what changes do you think I have in successfully repairing this monitor? Since that inconsiderate short-term thinking copper collector had cut the cord so closely to the case, I will have to open it up and solder the stumps off and solder a new 220V cable and a cable with a 9-pin D-sub connector back on the board inside. I guess it would have been the best option regardless, since patching up a shortened cable would have looked ugly.

Also, according to the Wikipedia page on the IBM 5151 monitor (http://en.wikipedia.org/wiki/IBM_5151), it might also be a good idea to check if the TFB648 needs to be replaced as well, since I'll probably have to open the monitor anyway.

Finally, what would the best way be to fix the crack in the plastic case? I know that it can't be made as new again, but what would the best method of restoration be? The right kind of glue, perhaps? Or is there perhaps a some more elegant alternative that would mask it somehow?

For the fun and sense of getting something working again alone it might be worth it, not to mention the educational aspect. Any pitfalls I need to be aware of?

modem7
April 23rd, 2010, 03:03 PM
From your photo, it certainly looks like the case damage was done by the copper scavenger. It looks as though, to get as much cable as possible, they've pulled on the cables with great force with the aim of breaking the case to expose the part of the cables inside the case.

Obviously, you are not going to be aware of the extent of the physical damage until you open up the unit.


Also, according to the Wikipedia page on the IBM 5151 monitor (http://en.wikipedia.org/wiki/IBM_5151), it might also be a good idea to check if the TFB648 needs to be replaced as well, since I'll probably have to open the monitor anyway.
Unless there is a visual indication of failure of the flyback transformer, a multimeter should reveal any open winding. Beyond that, tools such as a low-ohms meter, ring tester, HV probe might be required to diagnose a faulty flyback transformer.
Of course, if you replace the missing cables and find that the unit doesn't work, you could always just replace the transformer, but they are expensive. Better to investigate other possibilities first.

modem7
April 23rd, 2010, 03:19 PM
There is a SAMS COMPUTERFACTS for the 5151 at http://www.ibm5150.net/repair_center.html
That includes disassembly instructions and other information.

You may already know this. In any case, it serves as a warning for others. Powering up the 5151 whilst it's cover is off presents a safety risk, and should be avoided if possible. Also, after powering off the 5151, there may be voltage present for a while.

digger
April 23rd, 2010, 05:28 PM
Thanks for the info and advice, modem7! If they had indeed been pulling that hard on the cables, who knows how much damage they may have done inside. On the other hand, the fact that they still didn't manage to rip the cables out, but had to resort to cutting them after all is testament to the build quality of the equipment in those days. :)

I don't think I'll be getting around to tinkering with the screen soon, but I'll keep it safely stored for now. Meanwhile, if any of you have any additional advice on repairing this model, please share them here. Thanks.

Hyperfrog
April 23rd, 2010, 10:50 PM
Finally, what would the best way be to fix the crack in the plastic case? I know that it can't be made as new again, but what would the best method of restoration be? The right kind of glue, perhaps? Or is there perhaps a some more elegant alternative that would mask it somehow?

I think I would use 5-minute epoxy glue. It will be apparent, but only if you look at the bottom of the unit.

Chuck(G)
April 24th, 2010, 07:07 AM
On plastic (particularly ABS) cases, I use methylene chloride, a solvent cement. It's available from some hobby supply stores and commercial plastics places. It works by temporarily dissolving the plastic so that the resulting joint is as strong as the surrounding material. Epoxy, cyanoacrylate, and other "glues" tend not to adhere very well.

Another alternative is ABS plumbing cement. It's generally black and pretty heavy-bodied, so it's not cosmetic. But if you make your repair on the inside, using some fiberglass mesh to strengthen the joint, the repair can be strong and permanent.