25 Keyboard Fixed

[teenix]

Hi all,

I was trying to avoid it, but I had to strip the keyboard on my HP-25, half the keys weren't working.

It mostly went well. I just trimmed the plastic post tops and it pulled apart easily. I have the keyboard a good going over in an ultrasonic cleaner with isopropyl alcohol, but still had a few failures so I used my little plastic scrubber and cleaned under all the contacts. Now they work fine.

I gave the front panel and keys a work over using a light detergent solution in the cleaner and they came out nice. I didn't leave the front panel in long, I wasn't sure if the printed lettering would come off.

I used a hot glue gun to put the assembly together again. When I went to test it, the power switch was loose and worked intermittently, so I had to pull it apart again. The hot glue is good in this regard, it was easy to remove. I reattached it again and this time all ok.

A nice display now from my Woodstock CPU board.

cheers

Tony

[EdS2]

Oh that's good - of the many posts, you hot glued them all?

Sounds much easier and more reversible than fitting tiny screws or re-mushrooms the tops with heat.

[teenix]

Yes, I hot glued them all. I'm pretty sure someone from the Forum has already done this. It is easy to pick the glue off if need be. The glue is pretty tacky, so I think it will hold together due to the number of posts - strength in numbers.

The only issue was at the top end of the board there are two larger diameter posts. I had to apply some light pressure holding the circuit board and front panel together. The switch contact can become loose if this gap is too wide.

cheers

Tony

[rprosperi]

Nice job Tony. awesome to have a working HP-25, one of the most influential machines in HP's long history, based on stories I see posted here all the time.

You mentioned a plastic scrubber for cleaning contacts - can you post a pic of that, I've been looking for a tool to use for cleaning corrosion/crud that is less harsh than a fiberglass pen, for cleaning delicate areas.

Thanks

[John Garza (3665)]

Looks great Tony!

Glad to see another 25 restored. One of my favorite machines.

For cleaning under the keyboard strips, I've had good success with ultra fine sandpaper (800 grit) with a plastic backing as used in model building. Cut a thin strip, thread it under the metal ribbon - press down on the metal bulge and pull the sandpaper through. Usually only one pass is needed. When all the keys are done, I then spray with deoxit to flush out any residue. I have also tried a variant of your plastic scrubber, using an xacto knife to add holes and 'teeth' to the scrubbing end for more difficult jobs. I worry about the tradeoff on effective cleaning vs. damaging metal. In the end, corrosion is like cancer. If you don't get all of it - it will eventually spread in an oxygen atmosphere.

And I like the idea of using hot glue. You can pick it off more easily than slicing off the top of a gorilla glue mushroom cap like I use. I wonder how it will hold up over time though. When I refurb a Woodstock keyboard and switches, I don't expect to have to go back in there again in another 20-30 years. So I don't mind the tradeoff of a more time consuming disassembly for a more secure mechanical bond. But as you said: 'strength in numbers!'. Great thinking.

-J

[teenix]

(02-08-2024 12:57 PM)rprosperi Wrote:  You mentioned a plastic scrubber for cleaning contacts - can you post a pic of that, I've been looking for a tool to use for cleaning corrosion/crud that is less harsh than a fiberglass pen, for cleaning delicate areas.
Thanks

In my Classic Notes page 47. Just a simple tool made at home, it seems to work ok. You could use deoxit or isopropyl alcohol with it.

I started work for the phone company back in the 70's and one of the first jobs as an apprentice was oiling and dagging uniselectors and cleaning relay contacts. We used thin flexible strips with fibres on both sides. Sliding these between the contacts cleaned them really well. I haven't seen them since, but I wonder if something like this might work.

https://electrolube.com/product/ccs-cont...ng-strips/

cheers

Tony

[Massimo Gnerucci]

(02-08-2024 10:33 AM)teenix Wrote:  Yes, I hot glued them all. I'm pretty sure someone from the Forum has already done this.

I did it, years ago, on a Voyager. All went well.