Hope this is the right place to ask. IBM 5251Beamspring Question

[clickboyclick]

(Photos coming soon) I am currently restoring a 5251. Everything is going good ordered things I need replace broken switch and convert to USB. Very little corrosion good condition other than the normal rubber rot from the contamination shield and foam rot that holds the switches in place.

In all my googleing I have not found what to do about the rubber mat underneath the pcp board. In lots of photos and videos I looked up, I see that they are black which I can only assume is not original. Mine is clear and sticky and oily from degeneration. To be clear the mat I am talking about separates the pcp and metal from touching. Also I am not sure how to separate the board from the metal because how sticky it is.

I am worried I will break it if pull it off. How should I remove it and what should I replace it with? Also I bought this https://www.amazon.com/gp/product/B009ETBPXE to replace the foam that has rot that holds the switches in place. Is this good? Do you think a Non-Stick Silicone Mat cut into shape would work good between the pcp and metal?

[codemonkeymike]

2mm Art foam seems to be the standard for replacing the degrading foam, don't get too exotic with different materials unless you want to be a guinea pig. I get mine from Michaels (there all around the US). The answer to should you pull it off and replace it is, probably. If its falling apart and sticky then yes for sure. Removing the oily mess is a different story, I used a spackle to scrape it off then some acetone to remove the remaining goop. I'd recommend you check out the workshop section, or search for "beamspring restoration" there are some really great ones that people have done here.

Most recent post on the use of art foam for beamspring restoration:
photos-f62/ibm-3277-conversion-t18164.h ... am#p399286
workshop-f7/restoring-an-ibm-5251-beams ... am#p375233

[orihalcon]

I usually just wash and reuse the PCB insulation mat (that's what I've decided to call it today) though you could just as easily replace it. They can be black, clear, or even white from the factory, and I'd say clear is the most common. I'm sure you could replace with art foam if you wanted. It's really more of a rubber mat though, so if you were going for something more original, cutting a custom sheet of something like gasket rubber would probably be a little closer. If you are worried about degradation causing any damage to materials, you could always make one extra layer of plastic wrap above and below it and that shouldn't allow any further degradation products to get on anything else once you have it washed off. There probably isn't a wrong way to do it, and you probably aren't seeing much on replacement because most simply reuse

[codemonkeymike]

I must have mis read the post, the clear mat does not need to be replaced. It should be silicone, mine just needed to be cleaned with soapy water.

[clickboyclick]

I usually just wash and reuse the PCB insulation mat (that's what I've decided to call it today) though you could just as easily replace it. They can be black, clear, or even white from the factory, and I'd say clear is the most common. I'm sure you could replace with art foam if you wanted. It's really more of a rubber mat though, so if you were going for something more original, cutting a custom sheet of something like gasket rubber would probably be a little closer. If you are worried about degradation causing any damage to materials, you could always make one extra layer of plastic wrap above and below it and that shouldn't allow any further degradation products to get on anything else once you have it washed off. There probably isn't a wrong way to do it, and you probably aren't seeing much on replacement because most simply reuse

Yeah I am gonna have to replace it. I tried cleaning it with soap and water and it looked great. But 24hr later the mat smelt like chlorine and was oily again. The oil on skin after touching left residue that stung. Gross had to clean up area and wash hands. I put it in a bag.
After cleaning

24 hr later

I traced it on paper and took measurements. I need to find a rubber mat 20x20 inch (so i can cut into shape) thats .035 inch or 0.889 mm. Something tells me that mat use to be closer to 1 mm thick and shrunk over time.

[codemonkeymike]

I would say that even if it is oily and smells like decomposing plastic that you should still use it. My beamsprings mat was also slick and smelled of decomposing plastic but works just fine.

[clickboyclick]

I would say that even if it is oily and smells like decomposing plastic that you should still use it. My beamsprings mat was also slick and smelled of decomposing plastic but works just fine.

Really??? Idk it just seems odd to not replace it. My mat is really gross. I understand keeping it for originality but if it is degrading and smell bad I think it could hurt the board? Your mat is like that?

[codemonkeymike]

I would say that even if it is oily and smells like decomposing plastic that you should still use it. My beamsprings mat was also slick and smelled of decomposing plastic but works just fine.

Really??? Idk it just seems odd to not replace it. My mat is really gross. I understand keeping it for originality but if it is degrading and smell bad I think it could hurt the board? Your mat is like that?

Yes the mat in my beamspring does offgas and smells, as well as feeling slightly oily (possibly not as bad as your keyboards mat). I am not saying this as a "keep it original" kind of thing. I have other reasons. First IBM was good at making things. Second the mat tolerances need to be tight and most likely have to have some sort of insulating properties which may not be emulated by the new material. Third the decomposing plastic or whatever the oil is should not be hurting the PCB just a guess from the fact that all (most?) beamsprings have the same mat in them for the past 30-40 years.

[xxhellfirexx]

Where are both of your beamspring keyboards manufactured? The ones I got are made by CP Clare in Canada and none of the mats are smelly and oily. As for the fear of not replacing the mats because it may cause the keyboard to not work as well, why not test it? Stick a sheet of paper or other thin material between the mat and the PCB and see if the keyboard still functions well.