lubing breadbin c64 mitsumi switches.

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nerdhouse

06 Nov 2022, 03:23

hey everyone.

i just wanted to throw up a quick post to make a record of our results lubricating the mitsumi switches on our breadbin c64. i looked around and didn't see anyone discussing what lubricants worked well for them so i figured a few people might find this helpful.

our results were surprisingly good considering how crappy the c64 keyboard feels. after lubricating, it's significantly more usable than before. the mushy bottom out feel is still there, but that's unavoidable with this switch design. they are way less scratchy overall though, and the oil on the springs and lubricant on the rattly space bar stabilizer really reduced the unpleasant noise. i'm not sure how well it will hold up, but if they get significantly worse within a few months i will post an update.

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disassembly is a real pain. the caps are really tight on the stems and the springs aren't captive. they will go flying everywhere and are very hard to find. we had a few scares but managed not to lose any somehow. just be careful when you do this. it's a big pain in the butt.

we also had to desolder the latching switch because we wanted to really soak the entire mounting plate in water. this was not a big deal and was dead simple to reattach. the latching switch clicks into the housing from above. don't try to take they key apart while it's clipped into the housing, you need to take it out to disassemble it safely.

we cleaned all of the sliders and springs before lubricating everything. i wasn't sure how the weird rubber bits would hold up if we soaked the entire slider so we cleaned them individually with a rag.

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here's the lubricants that we used:
krytox 205g0 for sliders
krytox 105 oil for the springs
permatex 22058 for the stabilizer

we bag lubed the springs. just tossed them all in a bag, put in about 15 drops of 105 oil, and filled the bag up with air. shook 'em up for a few minutes and they were evenly coated. our stock springs were a looking pretty oxidized, so i imagine coating them with oil will help prevent rust going forward. be careful because the spring for the space bar is heavier than the rest of the springs. it might be hard to pick out if you mix them all up.

we used a small paintbrush to put a thin layer of the 205 on all the sliders. you really don't need much to do the entire keyboard, we used less than 2ml. after putting all the sliders back in from the underside of the plate, we added some 205 to the little grooves that keeps the sliders from rotating. we just stuck the paintbrush in there between the slider and the housing.

for the space bar stabilizer we put healthy dabs of the permatex on the four places that the stabilizer bar interfaces with the key and mounting plate. the stabilizers connect to the mounting plate on two little detachable pieces. we detached them and put some permatex between them and the mounting plate since they are a little loose in there and we didn't want them making a bunch of noise rattling around. i had this permatex lying around from working on some other stuff so we used it instead of the krytox 205 because it's cheaper and we wanted to put a big enough blob of it on the stabilizer that it muted the sound. they are pretty similar in consistency though and you might be able to use one or the other for this entire job.

for the latching switch, it's pretty easy to take apart. the bottom of the housing is clipped in place in two spots and easy to pop open. we used the 205 on the slider. it slides against a folded metal spring and is still a bit scratchy after lubricating it, but is overall a lot better. it's not used much so it's not the end of the world. we probably could have put some lube into the little wire bit that interfaces with the key to get it to latch, but it slipped my mind. it's kind of hard to get at.

and that was it. we reassembled and were all done.

there is only so much you can improve this keyboard because of the design of the switches, but we are happy we did it. it is definitely worth the trouble if you are going to type on your c64 a lot. if all you do is play games then you may want to skip this because it is pretty time consuming. i think coating the springs in oil is probably worth it though, since ours were starting to look a bit rusty.

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p.s. i'm going to try the krytox on the stackpole switches in my heathkit terminal some time soon, so i'll likely make a similar post about that one to let everyone know how it goes.

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