M122 bolt mod woes

[jmaynard]

So I'm having to bolt-mod an M122. I got the thing off eBay, and the action was crap all the way across. I opened it up to take a look, and every plastic rivet had sheared. Whee. Not only that, but a couple of the spring assemblies had fallen out and been lost entirely.

Unfortunately, I had not read up on the process more than "this is what you do", and didn't trim the ends of the rivets before drilling. Result: more off-center holes than not. When I reassembled it, I had several stuck keys. (I have a 3472 InfoWindow terminal that it will plug into, and I knew something was wrong when I powered it up and got "bip...bip...bip" out of the terminal, even before it was connected to a controller...)

So...sigh. An aggravating afternoon wasted, and probably a ruined barrel plate. Anyone have an M122 barrel plate they can send me?

Also, I will argue that it shouldn't be called a bolt mod, but rather an itty bitty teeny weeny screw mod. Damn, M2 hardware is tiny.

I'm also considering ordering a complete set of spring assemblies new from Unicomp, as well as a new latex sheet to replace the black rubber one. I'd just as soon not have to do this more than once more.

Anything else I should consider while it's in pieces?

[fohat]

I suggest that you buy a new one from Unicomp. By the time you buy a bunch of parts and pay shipping, you will probably be into 1/3 to 1/2 half the price of a new one which would be fresh, clean, and have native USB and a warranty.

But since your old one is now peeled apart, I would personally recommend that you do an ANSI modification and get a layout very similar to a modern conventional keyboard. Doing that would mean buying a handful of key caps (Enter, Left Shift, Backslash, numpad plus, along with 2 horizontal stabilizers and one vertical, plus whatever other caps you might want to re-name).

Not sure I understand what you have in your hands, but in doing a bolt mod the prep and drilling is the delicate and critical process.

[Muirium]

Would a new one be controller swap compatible with the old one? He's wanting to hook it up to a vintage terminal, after all.

[jmaynard]

The goal of this mod is to have exactly a 3270-layout M122. I'm going to replace the controller with a Teensy2.0++ running QMK, eventually, but the original controller will be kept long enough to verify that the keyboard actually works before proceeding with the QMK part.

I am buying a set of PC/3270 keycaps from Unicomp. The plan is to have the PC layout on layer 0, and the original 3270 layout on layer 1 (with keys mapped so that tn3270 will do the thing the key is actually labeled to do).

Then, once all that is accomplished...I'm going to build a Raspberry Pi 4 into it - and then run Hercules on that. The end goal is to have a mainframe version of the C64: everything built into the keyboard, but able to run mainframe software.

[fohat]

He's wanting to hook it up to a vintage terminal, after all.

Oops, skipped right over that part.

The goal of this mod is to have exactly a 3270-layout M122.

I am buying a set of PC/3270 keycaps from Unicomp.

I am pretty sure that Unicomp sells 3270 terminal keyboards, but what fun is that since you obviously like tinkering around with "unusual" projects?

Unicomp probably has everything that you need, I would contact them by phone or email because there are a lot of pieces and gear gathering dust on the shelves in that building that are not listed or accessible on the web site.

[Sheepless]

Then, once all that is accomplished...I'm going to build a Raspberry Pi 4 into it - and then run Hercules on that. The end goal is to have a mainframe version of the C64: everything built into the keyboard, but able to run mainframe software.

That sounds like an excellent project, but doesn't the Pi 4 run rather warm? There's not a lot of ventilation in an M122.

[jmaynard]

That sounds like an excellent project, but doesn't the Pi 4 run rather warm? There's not a lot of ventilation in an M122.

You're right, and I've thought about that...not sure what I'm going to actually do about it. Either some sort of small fan or else a thermal path from the Pi's processor to the backplate.

[Sheepless]

That sounds like an excellent project, but doesn't the Pi 4 run rather warm? There's not a lot of ventilation in an M122.

You're right, and I've thought about that...not sure what I'm going to actually do about it. Either some sort of small fan or else a thermal path from the Pi's processor to the backplate.

It's a shame it's not an F122, since that steel case bottom, being exposed to the outside, would probably make a better heatsink than the M122's backplate.

[XMIT]

I have... a LOT of M122s. I'll send you a PM.

[jmaynard]

It's a shame it's not an F122, since that steel case bottom, being exposed to the outside, would probably make a better heatsink than the M122's backplate.

You're right, but at the prices F122s go for, I'm not about to hack one up like this!

[fohat]

at the prices F122s go for, I'm not about to hack one up like this!

The converse perspective is to say that after going through this much work you want the best possible final product.

[Sheepless]

at the prices F122s go for, I'm not about to hack one up like this!

The converse perspective is to say that after going through this much work you want the best possible final product.

I love my F122, but I also have multiple M122s, and "best" in this context is really subjective.

[jmaynard]

The converse perspective is to say that after going through this much work you want the best possible final product.

I agree, but this project isn't worth a kilobuck to me...

[jmaynard]

Just to put a cap on the story, at least for now...

I have a parts-loaded M122 assembly coming, thanks to a forum member, and have gotten QMK downloaded and built. Once I get the keyboard modded and assembled, then I'll move ahead with the rest of the project.

[jmaynard]

So I got curious...and reassembled the one I have with the cracked and mis-drilled barrel plate, this time only using screws that had gone down the center of the rivets. I also separated and re-assembled the membranes after realizing that they weren't laying flat, and had a wrinkle at the left side of the keyboard. Once I did that, and made sure the flippers and springs moved freely at every stage of the reassembly, it worked when I got it together.

So now that I know what I'm doing, the next one should go better. Right?

[fohat]

the next one should go better

Without a doubt. As long as the layers are aligned and solidly together you should have a working keyboard. People have used binder clips around the edges (with the internal assembly out of the case, of course) to cobble together a temporary repair.

There are situations where many rivets are missing but it still works, because they are spread out randomly. The bigger problem is when a particular area is stripped out and loose and the moving parts don't move in the way they are supposed to.

[jmaynard]

IMG_20210531_125519 (1).jpg (1.13 MiB) Viewed 3230 times

It even works with QMK! Well, mostly: the right arrow in the cluster, the home key in the cluster, and the keypad enter keys do nothing. (And yes, they're all mapped to something in QMK.) I'm not going to worry about it right now, since I know I'm going to be stripping it down and replacing the barrel plate anyway. That protoboard isn't my prettiest work, either, but it'll do the job. I might get adventurous and see about getting PCBs made.

But it's (mostly) working, yay!

[zrrion]

Yeah, my first bolt mod was similarly complicated (bought entirely unsuitable bolts and the plate from unicomp wasn't 100% compatible with my M) but my next bolt mod went without a hitch. If you've got another barrel coming it should go much better.