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Model II Keyboard Differences - Further Analysis

Well, I hope its not some incompatibility between the A keyboard and the B machine that is preventing the space bar from working. I guess I have to finish my cable after all so that we can confirm if that is an issue. Man, I hate those DIN plugs. I might try your approach and join 2 existing cables. But, I do want to master soldering the DIN plug.

BTW, if anyone needs mylar disks, I just punched out a few hundred for a keyboard rebuild I am currently working on. I always use fresh mylar for all keys when rebuilding keyboards now. They work great on the Model II with those foam pads available on eBay. PM me an address and I'll mail them to you.

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After performing my first B design keyboard rebuild this weekend I realized another difference between A and B keyboards. I have rebuilt several A keyboards before so I was surprised by how much more exacting I needed to be when rebuilding the B keyboard. Alignment of pads and Mylar discs is critical. There are a number of keypads on the B pcb that have trace runs very close so it is easy to incur capacitance bleed which resulted in a bunch of garbage characters displayed per keypress. The G and J key seemed especially susceptible, so much so that I had to trim down my Mylar disc substantially for those keys.
 
Just FYI after getting the 8" to 5.25" prototype adapter board made up I am able to boot LS-DOS. And the space bar does work. As I suspected it was the bad Xenix install on the HD.
 
Interesting that under Xenix the space bar only is not working.

On my B design rebuild, I am finding more issues with spurious characters being generated on other keys. I suspect that either the mylar material I use is too sensitive or I just need to reduce the size of the discs. I have used 7/16" discs on several A design keyboards with no issue. The B design keyboard seems to be more sensitive. I will experiment with smaller discs.
 
Good luck Pete. Now I just need to order the foam pads from Germany. Or do you have a home made way? I had heard of using Air Conditioner filter material the gray kind. like foam before. And a punch. Just what size punch? I just need to rebuild the "Donor" keyboard. 84 keys
 
I tried creating my own foam pads using air conditioner foam and a 7/16 hole punch. It was time consuming but I was able to punch out decent quality foam pads. What drove me nuts though, was gluing the foam to the plastic discs and the mylar. I used contact cement and always made a huge mess. Then, if you did not dry it completely or if you used too much glue, the foam pad would stay squished when pressed as the cement penetrated the foam. The glue would get on my hands and then would stick to the mylar, etc. Just thinking about it again gives me the shakes.

I only buy the best from Germany now! :)
 
pski said:
I tried creating my own foam pads using air conditioner foam and a 7/16 hole punch. It was time consuming but I was able to punch out decent quality foam pads. What drove me nuts though, was gluing the foam to the plastic discs and the mylar. I used contact cement and always made a huge mess. Then, if you did not dry it completely or if you used too much glue, the foam pad would stay squished when pressed as the cement penetrated the foam. The glue would get on my hands and then would stick to the mylar, etc. Just thinking about it again gives me the shakes.

I only buy the best from Germany now! :)
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I used spray contact cement. and laid out the three layers as a large sheet. Punching 100 discs took about 20 minutes this way. Where do you buy them from?
 
kb2syd said:
I used spray contact cement. and laid out the three layers as a large sheet. Punching 100 discs took about 20 minutes this way. Where do you buy them from?
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http://www.ebay.com/itm/121266887970?

You still have to make the mylar discs.

I could see laying out the plastic, foam and mylar in whole sheets, gluing the sheets together and punching them out might be an interesting way to go though.
 
NF6X said:
That's exactly how I plan to try it. I have the stuff, but haven't found the gumption to mess around with spray adhesive yet. :)
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Trying to lay up the mylar on the wet glue with no wrinkles but at the same time not pressing on the foam so the glue does not penetrate the foam seems to be the most difficult part. Please record video if you attempt to do this so we can either applaud or snicker depending on the outcome. :)
 
I changed the name in my original post. Never tried anything else. Initial read through makes it sound very similar.
 
pski said:
Trying to lay up the mylar on the wet glue with no wrinkles but at the same time not pressing on the foam so the glue does not penetrate the foam seems to be the most difficult part. Please record video if you attempt to do this so we can either applaud or snicker depending on the outcome. :)
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I laid out the mylar sheet, and taped it down securely. Sprayed a light coat on it and the foam. Waited for it to get tacky (per the directions) then put the foam onto the Mylar. Easy peasy...
The stuff comes out like hairspray. You'd have to work at it if you wanted enough to penetrate the foam.
 
kb2syd said:
I laid out the mylar sheet, and taped it down securely. Sprayed a light coat on it and the foam. Waited for it to get tacky (per the directions) then put the foam onto the Mylar. Easy peasy...
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Ah..the mylar is the base. Yes.
 
And I did a SMALL area. You only need about 8 inch x 8 inch to get enough inserts for one keyboard. Make it manageable.
 
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The foam that I bought is much more firm than the original stuff. If it works, I don't know what it'll do to the keyboard feel. I have 2' squares of the foam and plastic sheet for the mounting base, so if it works at all, I will have a vast supply of pads! I'll use a space blanket for the aluminized mylar.
 
NF6X said:
The foam that I bought is much more firm than the original stuff. If it works, I don't know what it'll do to the keyboard feel. I have 2' squares of the foam and plastic sheet for the mounting base, so if it works at all, I will have a vast supply of pads! I'll use a space blanket for the aluminized mylar.
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The stiffer foam make it very brutal on the fingers. I speak from experience.
 
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