Scratchy Fluke 1720A Switches

[OldIsNew]

I picked up a Fluke 1720A Programmer keyboard - it's kind of a nice little board:

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I've got it working with a Teensy breadboard but before finalizing the case wiring I was wondering if anyone knows if anything can be done to refurb the switches - they're rather scratchy.

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From what I found on the Wiki they appear to be Datanetics DC-60s and I'm guessing the problem is likely dust contamination:

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They appear to have clips on the sides but I noticed from Wiki pics that they may also have welded plastic pegs holding them together as well. Does anyone know if its possible to open the switches non-destructively?

[Daniel Beardsmore]

The only person I know (other than me) who's ever opened one is Sandy, but his page is in Japanese:

http://sandy55.fc2web.com/keyboard/y1700.html

I did get one apart, but I definitely had to slice through it. I have an unassembled one somewhere and I'm still not entirely sure how they are assembled, but they certainly cannot be safely opened.

It's a shame, as I have a rare linear prototype/example that needs examining internally, but the only way to do that would be x-ray! Nothing whatsoever is known about it.

[OldIsNew]

I did get one apart, but I definitely had to slice through it. I have an unassembled one somewhere and I'm still not entirely sure how they are assembled, but they certainly cannot be safely opened.

Thanks for the info, I was kind of afraid of that. The switches aren't too bad but I was hoping could work on them a bit. Oh well.

Now I just have to learn some electronics - there's a solenoid with a driver circuit on the board - I need to get that working!

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[OldIsNew]

Well I may not be able to do too much about the scratchy switches, but I was able to get the solenoid working by running a circuit off the Teensy. The occasional squeaks from the switches aren't as noticeable! Now just have to do some proper permanent wiring.

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[Daniel Beardsmore]

I have a load of NOS DC-60 switches, but the lowest profile type, and those are squeaky. They're also nowhere near as tactile as the sample switch I got. I also have a sample linear switch that should not exist. There are still mysteries to be solved.

[OldIsNew]

Not motivated enough yet to open/clean all the switches, so I finished up the wiring for now and the board and it's solenoid is working. Luckily the solenoid appears to be 5V (at least its working on 5V) so I'm running it off the Teensy with a simple solenoid driver. I wasn't sure if hooking up the original driver circuit on on the board would work and just didn't feel like experimenting.

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Quick video of typing with the solenoid:

I will eventually clean the squeaky switches (maybe).

[JP!]

Hard to hear any squeaks over the solenoid

[Sangdrax]

Only difference between the old driver on the board and your new one I can see is you swapped the Opto for a BJT and left out the capacitor. That's is a nice capacitor too. I didn't know they put tantalums in stuff that old.

Love the video and the sound.

[Wodan]

What a stunning little project. The PCB is a piece of art without the solder mask and the beautiful silver traces.
Good luck cleaning those switches, sounds like an intense adventure to figure out how to disassemble them!

Reminds me of the Marquardt Ergo Mini which is a beautiful board with horribly scratchy/bindy switches that I am afraid to break when opening them ... Maybe the board could be nice with some lube? I might never find out hehehe

[seebart]

What a stunning little project. The PCB is a piece of art without the solder mask and the beautiful silver traces.

OldIsNew is doing awesome projects like this all the time.