deskthority

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.

Adjust the voltage threshold and find the sweet spot

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.

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

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?

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.

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.

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

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!

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.