Omnikey key bounce?

[ander]

Hey guys,

I was lucky enough to find a Northgate Omnikey Ultra recently at a thrift-store price. (Yes, it can happen to any of us!) It has Alps whites (I suppose it was unrealistic to expect blues, LOL).

There's just one problem: A few keys have what used to be called "key bounce"—they generate multiple characters when pressed once. It doesn't happen each time, but randomly.

I have all the board's DIP switches in the OFF (down) position, which I understand is correct for modern PCs. I've tried the board on native PS/2 and through a USB adapter, with the same results.

Is this necessarily a controller problem? Or can Alps whites get like this over time? Any diagnostic/repair advice? Thanks, A.

[fohat.digs]

I have seen that with Alps, and even Matias, and it is not an age or wear thing, as far as I can tell. I wonder whether the part of the mechanism that senses contact is just more sensitive.

[CPTBadAss]

You could try taking the switch apart and cleaning it with isoproyl alcohol or an ultrasonic cleaner. The nice thing about Alps is that you can take the switch apart without desoldering anything. And check the solder joints for cold joints.

And congrats on the find!

[didjamatic]

Congrats on scoring an omnikey.  Sometimes the bounce will reduce with use but it can annoy until you break it in.  It's easy to swap guts on switches with those from less used keys like scroll lock, print screen, etc.  Easy to change.

I LOVE Northgates.  Them and IBM PC AT Model F are my absolute favorite vintage keyboards to type on.

[chyros]

Congrats on the find!

I have to say I haven't had key bounce with any of my Alps keyboards yet. Have had it with Alps-like switches, but not with Alps themselves.

[opensecret]

If none of the suggestions here does the trick, contact Bob Tibbetts at http://www.northgate-keyboard-repair.com/.  He has a ton of experience working on these boards, and I've found him very helpful.  If you like big, solid, heavy, and function keys on the left where the Lord intended them, the Ultra is a great board, so it's worth getting it working right. 

[ander]

Hi guys,

Thanks for all your feedback. It's fun seeing all the enthusiasm about these nice boards, too. I'd read about them for some time, but never expected to have one as they'd become so pricey.

You could try taking the switch apart and cleaning it with isoproyl alcohol or an ultrasonic cleaner. The nice thing about Alps is that you can take the switch apart without desoldering anything. And check the solder joints for cold joints...

Sure, I'll try cleaning the switches in question. What's a "cold joint" though?

It's easy to swap guts on switches with those from less used keys like scroll lock, print screen, etc.  Easy to change.

Yup, that's a logical next step.

Sometimes the bounce will reduce with use but it can annoy until you break it in...

This one looks like it was hardly used, and there was negligible dust when I opened it. So indeed, maybe it's working too well, and just needs to be broken in... Can that really happen?

If none of the suggestions here does the trick, contact Bob Tibbetts at http://www.northgate-keyboard-repair.com/.  He has a ton of experience working on these boards, and I've found him very helpful...

Yes, I'd heard about Bob and what a great reputation he had. Before I mail off something this big and heavy, though, I think I'll give it a shot myself first—I may actually learn something.

If you like big, solid, heavy, and function keys on the left where the Lord intended them, the Ultra is a great board, so it's worth getting it working right.

LOL. Sorry, OS, but I've already remapped the F-keys to the top row. (Maybe I'm an unusual typist, but it seemed like my fingers were already pointed that way.) I'll ask the Lord for forgiveness. Considering She created time and space themselves, She probably knew I was going to do the remapping thing even before I did. I mean, it's hard to imagine Her slapping Her Forehead and saying, "Dang—I was sure that guy was going to use the side keys!"

[CPTBadAss]

Cold joint is where your solder joint is there but isn't properly connecting the two contacts. In other words, your solder joint is ****ed up so fix it.

[jacobolus]

There are two parts that combine to make keys “chatter” or “bounce”.

(1) Insufficiently robust debouncing routine in the keyboard firmware, caused either by too slow a scan rate + too fast a decision rate for key status, or by a poor decision algorithm. Many old keyboards had pretty lame debounce routines; the fix is to rip the controller out and replace it with a Teensy or something with one of the open source keyboard firmwares on it.

(2) Poor signal through the wiring and the switch itself, caused by some combination of poor switch engineering, dirty switch contacts, bent switch internals, bad solder joints, failing components, or similar. Alps switches are actually incredibly well engineered from a signal perspective (much better than Cherry MX which are a little bit chattery even at their best, see here https://geekhack.org/index.php?topic=42385.msg855693#msg855693), because the contacts are entirely shielded from contamination by the plastic switchplate assembly, but the little contact leaf that the slider presses into the contact plate can get bent out of shape so it’s not pressing the contacts together, especially if the keyboard was stored with the keys held down for a decade or two. As other folks have mentioned upthread, it’s also possible for solder joints to get a bit dodgy, or to have other wiring issues. Try using a multimeter to test the continuity across the switch and between the switch pins and the controller I/O pins.

If it’s the switch, then you can try bending the internal leaf back into shape, or you can desolder and replace the dodgy switches. If it’s a solder joint, you can reflow that joint. If there’s are some busted traces on your board, you can wire around them. Etc.

[ander]

Cold joint is where your solder joint is there but isn't properly connecting the two contacts. In other words, your solder joint is ****ed up so fix it. ;)

Ah, "cold" as in "no current"—I get it. Thanks!

There are two parts that combine to make keys “chatter” or “bounce”.

(1) Insufficiently robust debouncing routine in the keyboard firmware, caused either by too slow a scan rate + too fast a decision rate for key status, or by a poor decision algorithm. Many old keyboards had pretty lame debounce routines; the fix is to rip the controller out and replace it with a Teensy or something with one of the open source keyboard firmwares on it.

(2) Poor signal through the wiring and the switch itself, caused by some combination of poor switch engineering, dirty switch contacts, bent switch internals, bad solder joints, failing components, or similar. Alps switches are actually incredibly well engineered from a signal perspective... but the little contact leaf that the slider presses into the contact plate can get bent out of shape so it’s not pressing the contacts together, especially if the keyboard was stored with the keys held down for a decade or two... If it’s the switch, then you can try bending the internal leaf back into shape, or you can desolder and replace the dodgy switches...

This is all great info. I disassembled my first Alps switch tonight (I lubricated the Enter key, which was a bit sluggish—works great now), so I understand the switch mechanism.  I'll try your suggestions in escalating order.  :?)

[ander]

BTW, I just realized the upper SF1–SF12 keys default to F1–12, so I didn't need the remapper, obviously. I'd just assumed they were programmable keys that needed special software.

[chyros]

BTW, I just realized the upper SF1–SF12 keys default to F1–12, so I didn't need the remapper, obviously. I'd just assumed they were programmable keys that needed special software.

The SF keys are SPECIAL (SF) keys, not PROGRAMMABLE (PF) ones such as on the AnyKey. The idea is to use the SF Select button and then a modifier key (alt, shift, ctrl). This sets the SF keys to register as alt+F1, shift+F1 or ctrl+F1. SF Select + Esc resets them to normal F keys. See the OmniKey manual attached on Deskthority for more info .

[jacobolus]

Ah, "cold" as in "no current"—I get it. Thanks!

Cold joint = one of the pieces of metal you were soldering together wasn’t hot enough (or wasn’t clean enough) so the solder didn’t wick to it and make a good electrical contact.

Typically you get cold solder joints when someone melted the solder with their iron directly, instead of using the iron to heat all of the metal contacts to above the solder melting point and then feeding the solder into the joint.

You can usually fix these by just heating the joint back up to above the solder melting point, whereupon the solder will flow on to the surface it didn’t join with the first time, but if that doesn’t work you can suck the solder out and then re-solder the joint.

[fohat.digs]

heating the joint back up to above the solder melting point, whereupon the solder will flow on to the surface it didn’t join with the first time

It has always been counter-intuitive to me that the melted solder should flow TOWARD the heat.
 

[jacobolus]

https://en.wikipedia.org/wiki/Wetting (though that article mostly talks about water rather than solder)

Basic idea is that the solder sticks to the hot copper leads/pads (adhesion) more strongly than it sticks to itself (cohesion). It doesn’t stick at all to cold copper.