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HOWTO: Repair a Kaypro Keyboard (or Apple Lisa or SOL)

atod

Experienced Member
Joined
Oct 14, 2010
Messages
303
Location
New York, NY
My Kaypro keyboard works again! Here is a write-up of what I learned from a few other how-to documents. This in no way my directions on how you should perform this repair at all. Please do not try these steps unless you are an experienced professional and can hold me harmless for your actions.

Time:
This will take about three hours or disassembly, creation, assembly and test. Gathering all the materials and tools will also take time. Overall it took me about three months on/off work to wait for items from Ebay and visit stores for the other items and the finish the repair. Hopefully this list will reduce that duration.

You will need:
+ Rubber Cement (or contact cement if you have patience)
+ Open Cell Foam Block
+- I purchased my block from www.foamforyou.com. I sampled many types
from them and found "Premium Medium High Density aka HD 36" worked the best.
Some folks say you can find this at an Arts & Crafts store. Good luck. I searched a couple
and no soft open cell foam.
+ 7/16" leather hole punch (find this on Ebay or Harbor Freight for cheap)
+ Hammer
+ Space Blanket (Ebay or Wallmart)
+ Pieces of cardboard to hold under the punch
+ Nichrome Wire (To cut the foam, available for cheap on Ebay)
+ Piece of wood with 2 drywall screws, the length of the foam block
+ 12V power supply with at least a couple amps (to power the nichrome wire)
+ Voltmeter (to test continuity)
+ Ruler that measures .2 inches, maybe a caliper ruler
+ Dental pick or similar picking device
+ Tweezers

1. Disassemble your keyboard, remove the key switch assembly from the printed circuit board

2. With the underneath of the key switches exposed you will notice the foam has deteriorated. You need to replace it.

3. Each foam insert has a silver mylar circle exposed on top and a stiff circle of plastic hidden underneath. We don't care too much about the mylar because it almost always needs replacement.

4. With the dental pick, reach under/behind the deteriorated foam and under the plastic circle. Pull the foam assembly with both discs out of the key switch. It should just pop out as you flex the hidden plastic circle with the dental pick.

5. Do this for each key switch foam insert. Be careful to save the clear plastic circles. You will use them later. The old deteriorated foam and mylar can be discarded.

6. Clean off the clear plastic inserts. I let them soak in alcohol the scraped them clean and dried on paper towels.

7. Now we need to "make" a new set of foam circular inserts and circles of mylar. At this point you have either purchased the recommended foam or have some foam of your own. Before creating all the foam inserts, I suggest making only one and trying it out. This way, if the foam is too stiff or soft you can make a change in the foam type before punch the rest of the foam inserts.

8. Create a nichrome foam cutter like in my picture below. Use the two drywall screws as posts to hold the wire off the wooden board. Measure 0.2" high on each side of the posts and wrap the wire there. Double check that the height is around 0.2" the entire length of the wire and do whatever is necessary to keep the nichrome wire tight. When it heats, it stretches. Some people even use springs on each side of the posts to take in the slack when the wire heats.

9. Connect the positive and negative to the 12V power supply. I used 14 gauge wire and alligator clips to hold this jury rig together.

10. Momentarily turn on the power while sliding the foam block through the jig. You should hopefully be cutting relatively straight 0.2" large squares of foam. Other people encourage use of two razor blades held together 0.2". It doesn't work well. The nichrome wire had a cleaner cut.

11. When you have made enough 0.2" foam to punch out enough keys, stop.

12. Lay down a piece of cardboard on a hard surface.

13. Lay the 0.2" foam over the cardboard and use the 7/16" hole punch to punch out enough foam inserts. Use the hammer. Be careful to punch straight. Look at the results as you go. Another trick I found is to make a couple punches, rotating the punch a 1/4 turn each punch. This makes the punch clean.

14. When you have enough foam inserts, it's time to make the mylar circles. Get your safety blanket and fold it a few times.

15. Place the folded safety blanket over the cardboard. Use the hammer to hit the punch through the mylar. Hit it hard and it should result in may cicular layers stuck together cleanly cut.

16. Take your fingers and rub the thick circle of mylar together. Many other pieces will fall out. Keep squeezing the mylar and make sure you only have a single ply/layer of mylar left. You want to separate all the mylar into single piece/layer circles. I found that many times I thought the circle was only one piece but later on, discovered it was two pieces stuck together. Similar to when you accidentally miss that page in a magazine or a book.

17. When you have separated the mylar circles, it's time to test continuity. The *non-conductive side of the mylar must make direct contact with the circuit board*. Test continuity flipping mylar discs as you go.

18. When you have identified and flipped all the discs correctly, it's time to glue them to the foam.

19. Hold the disc with your tweezers and apply rubber cement (or contact) to the *conductive* surface (the side we don't care about). Stick that to the foam.

20. Follow the same procedure to glue the clear plastic discs to the foam.

21. Wait to the rubber cement to dry. It's a little over an hour.

22. Pop all the foam inserts back in. I line them up into the key switch then use a dental pick to push the hidden clear plastic circle down. The key switch has 4 latches around the disc. As you push each latch location at 12, 3, 6 and 12 oclock' you will hear the disc pop back in.

23. Before completely screwing your keyboard back together, test it. Get whatever you can connected again and start pressing keys. If you encounter an issue, try keeping the keyboard unscrewed and tapping the foam inserts manually against the PC board.

24. Don't rule out the following issues which I may have encountered.

One of the specialized ICs may be damaged. For me, I found the Caps Lock and Shift keys were behaving incorrectly and traced the behavior back to either the XR22-950-3B or XR22-908-03 ICs. I ordered them through seekic.com from China for total of $30 w/ S&H. When removing the old ICs I found a break in a trace. That may have been the real root cause or perhaps it was my screwdriver lifting the old IC out. Just be aware of that.

My keyboard works great! Good luck folks!











 
Last edited:

GADFRAN

Experienced Member
Joined
Dec 1, 2007
Messages
318
Location
Allentown, Pennsylvania, United States
Thanks for adding so much specific detail to our Kaypro knowledge base on this web site for all to benefit for all your hard work.

Much appreciated by many I am sure.

All the best with your future "adventures" with Kaypros !

Frank
 

kyeakel

Experienced Member
Joined
Jul 27, 2009
Messages
491
Location
Curwensville, PA
This will also probably work for Tandy Radio Shack Model 2 and 12 keyboards, the measurements and construction details seem to along with what atod has described. atod any chance you want to punch out a bunch of these and sell them as kits?
Kipp
 

atod

Experienced Member
Joined
Oct 14, 2010
Messages
303
Location
New York, NY
Kipp. I asked someone else the same question and their reply was "no way!".

I don't have enough foam to do this. I would need to order another block which I'm thinking is about $25. I would also have to procure the correct clear plastic (for the bottom pieces).

If there is enough demand here, I could do something like this like Dwight did for the hard sector punch. I would need to see that at least 20 people would purchase a full set of foam inserts. I'm guessing they would be at least $35/set for me to even break even on labor. It's at least an hour to punch and glue everything. Trust me, this isn't fun labor like copying disks or tracing bade ICs. It's sweatshop messy labor.

Nick
 

atod

Experienced Member
Joined
Oct 14, 2010
Messages
303
Location
New York, NY
This will also probably work for Tandy Radio Shack Model 2 and 12 keyboards, the measurements and construction details seem to along with what atod has described. atod any chance you want to punch out a bunch of these and sell them as kits?
Kipp

Another thought that would make things easier on me and easier on the buyer:

- I could procure more foam which using my nichrome cutter I could cut to 0.2"
- I could then punch at least the amount of keys worth of foam inserts for the keyboard
- I could also punch a bunch of mylar circles

- It would be up to the purchaser to separate the mylar, check conductivity, glue the mylar to the foam, glue their old clear plastic dics to the other side of the foam

That would make things much easier on me and would save the purchaser buying items to punch or hot cut foam.
 

atod

Experienced Member
Joined
Oct 14, 2010
Messages
303
Location
New York, NY
NOTE: Someone has suggested using the Mylar from inside I potato chip bag. I haven't tried this. I suspect that mylar is thicker and more resilient then the space blanket. You may want to try it on one foam pad to *test* it out.
 
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