Help with beam spring chatter when solenoid is enabled

nurupism · 21 Jun 2017, 17:13

Hi, I recently managed to acquire an IBM 3278 pre-modded with an xwhatsit controller and solenoid driver.

When typing with the solenoid on, though, I noticed that sometimes I get keys that would repeat twice. This chatter isn't limited to a single switch, and only happens when the solenoid is enabled. Naturally I could always avoid using the solenoid, but I'd hate to waste such a neat feature.

I've seen one potential community fix for the debounce code in this thread, but it looks like that's for the Model F controller and not beam spring.

Has anyone else experienced something similar? I'd love to get some advice on how to fix this issue.

wobbled · 21 Jun 2017, 18:34

Adjust the voltage threshold and find the sweet spot

nurupism · 21 Jun 2017, 19:19

wobbled wrote: Adjust the voltage threshold and find the sweet spot

It was one of the first things I tried. Increases in voltage threshold reduces frequency of chatter, but it still persists. There isn't really a higher value I can sit on that lacks chatter and doesn't trigger neighboring keys.

orihalcon · 22 Jun 2017, 00:40

You might try mounting the solenoid differently and see if that changes it at all.

nurupism · 22 Jun 2017, 02:20

orihalcon wrote: You might try mounting the solenoid differently and see if that changes it at all.

I can try that. I guess the chatter is primarily caused by the solenoid making the PCB and switches vibrate, causing additional accidental contacts, right? Would adjusting the solenoid timing help as well?

hypkx · 05 Jul 2017, 22:31

Did you reach anything with the other mounting option. I have also switch chatter on mine current solenoid use. I put some foam under the solenoid, but its still there (but less). Next I will test the solenoid unmounted to see if it is really the vibration.

orihalcon · 06 Jul 2017, 03:25

May seem straightforward, but make sure everything is grounded well. I usually don't get too excited about grounding for Model F's, but it has made a difference on at least one beamspring solenoid setup I had were there was pretty excessive chatter and grounding pretty much completely took it away.

hypkx · 06 Jul 2017, 10:24

Ok, I will look into it. I will probably finish today my 3178, let's see if I have the same issue.

nurupism · 06 Jul 2017, 16:45

orihalcon wrote: May seem straightforward, but make sure everything is grounded well. I usually don't get too excited about grounding for Model F's, but it has made a difference on at least one beamspring solenoid setup I had were there was pretty excessive chatter and grounding pretty much completely took it away.

That sounds interesting, I'll give it a try and see if it makes a difference. Thanks!

hypkx · 07 Jul 2017, 12:38

My 5251 is usable, but still has some chatter, I will look what I can do about the grounding (but the solenoid is screwed on and the grounding cable fron the, controller also, I think I can't make it better).
I assembled my 3178 yesterday, with solenoid activated it has extreme chatter. I already tried adjust voltage, but it's without missing keys not further possible. I mounted the grounding pins with cables I had laying around, I will try to use thicker cables this weekend.