deskthority

That is so epic I would love to compare it to my fully restored XT to see how much wear from usage has changed the key feel. If you haven't done so already, I would suggest checking the foam layer without taking the assembly apart (degrading type will smear black residue on your finger). Even if it's NIB the foam may need to be changed if it's the crumbly/degrading type. I attached a side by side to show the difference.

That sound makes me giddy. Definitely an epic find. I have one in box that looks absolutely pristine but the foam is like the first one pictured which you can see has no recovery left. Definitely a luck of the draw when it comes to foam.

I wonder what factors determine foam condition, as I have two XT's sourced from the same place, one with near-mint original IBM foam and the other with the gross sticky stuff.

Bass wrote: ↑I wonder what factors determine foam condition, as I have two XT's sourced from the same place, one with near-mint original IBM foam and the other with the gross sticky stuff.

Looking at the two I have side by side. The good/non-degrading foam version still has some thickness compared to the degrading type, which is so thin and rotten it practically falls apart when handling it. No need to change it out right away if you have the crumbly type. I put my restoration off for a year before I had enough time to tackle it.

tron wrote: ↑That is so epic I would love to compare it to my fully restored XT to see how much wear from usage has changed the key feel. If you haven't done so already, I would suggest checking the foam layer without taking the assembly apart (degrading type will smear black residue on your finger). Even if it's NIB the foam may need to be changed if it's the crumbly/degrading type. I attached a side by side to show the difference.

Yes I definitely need to check the foam!

Bass wrote: ↑I wonder what factors determine foam condition, as I have two XT's sourced from the same place, one with near-mint original IBM foam and the other with the gross sticky stuff.

Your audio and video skills are strong! Excellent indeed!

IBM definitely switched foam material used at some point. The degrading foam was probably the earlier variant. IBM refurbs seemed to often be replaced with the non-degrading foam as evidenced by the 3178 model F's I've seen with repair detail stickers inside having the non-degrading foam, whereas those without repair history had the degrading foam still there.

There's a good chance you won't ever need to replace the foam even if it is the degrading type. I think Model F's (if properly taken care of from new) won't need refurbishing for a very long time if ever. Most of the ones we see were exposed to industrial dust/environments as well as stored out in the elements, and seems like most of the time, even the rough looking ones register all keys just fine.