Maximum acceptable resistance in IIe key switch

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Last seen: 5 hours 11 min ago
Joined: Jun 6 2020 - 10:50
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Maximum acceptable resistance in IIe key switch

I bought a supposedly tested and working numeric keypad for my IIe. And of course it's not fully working. Half the keys don't work. Opened it up to find that someone spilled coffee or coke in this thing 30+ years ago, and it never got cleaned up. I desoldered all the switches and started tracing out the PCB. Looks like I'm going to have to make 12 bodges.

 

 

But the switch that took the brunt of the spill has a little higher resistance than the others, despite my efforts to clean it. It's the short black style that uses a rubber dome with a conducive pad. All the other switches read 50-90 ohms. Best I can seem to get this one is mid 200s. Sometimes a little higher, sometimes a little lower.

 

 

Ultimately my question is, will that still work? Or is it too high and I'm the market for a replacement?

 

 

Thanks!

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I'm sorry, I'll show myself out...
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Last seen: 5 hours 11 min ago
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Don't quit your day job. :) I

Don't quit your day job. :)

 

I had an idea. Take that switch and temporarily try it in a position I know works. So I tacked it in and hooked the board up. It works. So it seems the keyboard is fairly tolerant of resistance on the switches. And now I can solder all the switches back in, and then my bodge wires.

 

 

If anyone cares exactly what switch they used, I can see there is an Alps logo on the bottom. After googling a bit, they are the Alps integrated dome switch. Specifically the black cross version on this page. 

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