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Cherry MX compatible upgrade for Mitsumi 99/4A keyboards


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8 hours ago, visrealm said:

I've had no issues with the 7x7 array of adapters. I'm using an Ender-3 V3 KE with a textured PEI build plate. It could be that my printer (and hence my nozzle and build plate) is relatively new (5-6 weeks).

I've had my E3 for 5 years plus now and it's so heavily modded, I hesitate to call it an E3 Pro anymore 😁. I love my glass bed over the textured beds. Smooth face on no base adhesion except for tiny little parts. I THINK if I slow down the print, I could get the array to print.

Last evening I tried using PETG (tougher and finer finish) for an adapter and I think I prefer it to the PLA.

Just FYI, Kailh black keys can be had for $40 or so for 120 on Amazon.

I have yard work to do today but, this evening I'll crank up the printer again.

OBTW, I used JLCPCB to order some boards. I currently have a discount with them and saved about $20. 

 

Once again, thank you @visrealmfor your efforts and as was mentioned in the other forum - time to buy up some mitsumi keyboards before the Ebayers catch on and jack up the prices.

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10 minutes ago, Duewester said:

Once again, thank you @visrealmfor your efforts and as was mentioned in the other forum - time to buy up some mitsumi keyboards before the Ebayers catch on and jack up the prices.

Seriously... they are already trying to get around $100 for TI keyboards, irrespective of make, model, or condition.  God help us if they put two-and-two together and jack up console prices. 😠

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On 4/15/2024 at 12:54 AM, visrealm said:

I've just uploaded a build video covering the entire upgrade process for those who are interested (currently unlisted):

 

KEYBOARD/4A-99 Cherry MX compatible upgrade procedure


https://youtu.be/9g29EfUJuLM

So happy for the YT. I had missed the part where I needed to reuse the Space Bar end pieces. Good point about the soldering timeline. And doggone that's a tiny switch for the Alpha Lock. My print(s) are not hugging it very well and I'm afraid to make it too tight. I'll get there though everything else has worked out pretty well. I'm doing most of the pieces in PETG. I think it is stronger and my tolerances seems to "Tolerate" it better than PLA. 

Thanks again for all you work.

OBTW - PCB's scheduled to arrive the 23rd. This one (I call it my Ti99-4aW Polished) has some goofy keys and is a good candidate to see if I can make your board work on it. The aluminum was all mangled, glued and taped when I got it so I decided to polish it and paint it. It's actually quite attractive😍

image.thumb.png.15474b1b651a4179a37917e1f048be38.png

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8 hours ago, Duewester said:

So happy for the YT. I had missed the part where I needed to reuse the Space Bar end pieces. Good point about the soldering timeline. And doggone that's a tiny switch for the Alpha Lock. My print(s) are not hugging it very well and I'm afraid to make it too tight. I'll get there though everything else has worked out pretty well. I'm doing most of the pieces in PETG. I think it is stronger and my tolerances seems to "Tolerate" it better than PLA. 

Thanks again for all you work.

OBTW - PCB's scheduled to arrive the 23rd. This one (I call it my Ti99-4aW Polished) has some goofy keys and is a good candidate to see if I can make your board work on it. The aluminum was all mangled, glued and taped when I got it so I decided to polish it and paint it. It's actually quite attractive😍

image.thumb.png.15474b1b651a4179a37917e1f048be38.png

Thanks for the updates.

 

I'm doing some test prints with PETG today. As this is all relatively new to me, I've only just bought my first rolls of PETG. Did the 7x7 switch adapters in it - turned out pretty swell. It seems a tad softer than PLA.

 

Just looking at your white wonder - the keycaps don't look Mitsumi (too rounded), so you'll need to invent adapters for them which might change the overall height.

 

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13 hours ago, visrealm said:

Thanks for the updates.

 

I'm doing some test prints with PETG today. As this is all relatively new to me, I've only just bought my first rolls of PETG. Did the 7x7 switch adapters in it - turned out pretty swell. It seems a tad softer than PLA.

 

Just looking at your white wonder - the keycaps don't look Mitsumi (too rounded), so you'll need to invent adapters for them which might change the overall height.

 

The Keycaps are actually quite similar. It's the Key switch that's different (taller than MX keys). The way the PCB is built is also significantly different. It's not a box, the key switches mount directly to the PCB. 

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Board is built. I used the insert style verses the self tapping for the space bar and mounting brackets.

Did key switches individually. The Kailh switches are just loose enough that they can twist a little and cause keys to look crooked.

I reprinted my PCB stiffeners, the screws were too loose so I reverted my horizontal expansion setting to default of -0.2. They are nice and tight now.

The spacebar is great. Great job on the engineering there.

Unfortunately for me, my PETG adapters for the keys seem to have worn out or something. What fitted great a couple of days ago now won't hold the cap on the switch 😭. I reprinted some with new new horizontal expansion settings to tighten them up and they kinda work.

I'll see about some pictures tomorrow.

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No, you're not seeing things. There are Blue and Black (and one white) key switches.

I'm using PETG - doesn't snap break like the PLA- and m3 nylon screws in the inserts. Currently printing all new adapters for the keys. The originals jus wouldn't stay on after a few dozen strokes. Almost like they wore down or the Kailh switch stretched. PLA adapters just never would fit right, either too big or too small. Maybe it's the hardness of the PLA that wouldn't give enough to snap in.

The wires are some silicone multistrand jumpers I had around. I though "Flexibility" might be called for here. My next one will have a rainbow ribbon that I removed from the Frankenine version one keyboard.

OBTW, after I took the picture I put some black tape on the wires where they cross the brace. The braces have a strip of Kapton tape on the back to insulate them from the PCB.

image.thumb.png.f138c061c47f9e81e3a15beda6e9ae56.pngimage.thumb.png.f501946be6e4bde233b37006f0702bdc.pngimage.thumb.png.be29c9def7c9ea50f8ce674071360d22.pngimage.thumb.png.da26ca213c4b818d41e37f34d5706f8b.png

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11 hours ago, Duewester said:

No, you're not seeing things. There are Blue and Black (and one white) key switches.

I'm using PETG - doesn't snap break like the PLA- and m3 nylon screws in the inserts. Currently printing all new adapters for the keys. The originals jus wouldn't stay on after a few dozen strokes. Almost like they wore down or the Kailh switch stretched. PLA adapters just never would fit right, either too big or too small. Maybe it's the hardness of the PLA that wouldn't give enough to snap in.

The wires are some silicone multistrand jumpers I had around. I though "Flexibility" might be called for here. My next one will have a rainbow ribbon that I removed from the Frankenine version one keyboard.

OBTW, after I took the picture I put some black tape on the wires where they cross the brace. The braces have a strip of Kapton tape on the back to insulate them from the PCB.

image.thumb.png.f138c061c47f9e81e3a15beda6e9ae56.pngimage.thumb.png.f501946be6e4bde233b37006f0702bdc.pngimage.thumb.png.be29c9def7c9ea50f8ce674071360d22.pngimage.thumb.png.da26ca213c4b818d41e37f34d5706f8b.png

Nice work. Thanks for the update.

 

The keycap adapters are always going to be the trickiest part to get right - the tolerances are very small. Mine worked well in PLA. I've since tried PETG and have found the retaining bumps on the adapter stem do seem to wear down.

 

Is the main issue the connection of the adapter to the switches? or the keycaps? It sounds like the switches, but if it is the keycaps, the spacebar-specific adapter might work better. The only difference is the retaining bumps on the stems are 0.1mm larger.

 

I might try and pick up a few different brands of switches to try as I've only tested the Akko switches linked in the repo.

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@visrealm,

Frankenine has a new Keyboard. Unfortunately, I had previously altered the beige box to get my other keyboard to fit so now there is a gap below the space bar.

image.thumb.png.f2b5cca6dc1035dd98454918e0b9de1b.png

I started working on the 99/4aW. The key switches are taller and the space bar has a different setup. I'm "Stretching" the PCB mounts (left and Right) 8mm to compensate for the key switches. I don't know what I'll do about the Space Bar yet. The supports are a few mm's wider than the Mitsumi. Too close for an adapter unless I can come up with some Offset of some kind.

image.thumb.png.f8ae548ec827d8003562324ab0a1edfc.png

image.thumb.png.00c3e0086f43ec989f4b025e638dbbc8.png

image.thumb.png.6c533beb01735356e5e57c6eaa009bb2.png

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3 hours ago, Duewester said:

@visrealm,

Frankenine has a new Keyboard. Unfortunately, I had previously altered the beige box to get my other keyboard to fit so now there is a gap below the space bar.

image.thumb.png.f2b5cca6dc1035dd98454918e0b9de1b.png

 

It's great to see Frankenine with original keycaps. Didn't recognize him 😁

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3 hours ago, Duewester said:

@visrealm,

 

I started working on the 99/4aW. The key switches are taller and the space bar has a different setup. I'm "Stretching" the PCB mounts (left and Right) 8mm to compensate for the key switches. I don't know what I'll do about the Space Bar yet. The supports are a few mm's wider than the Mitsumi. Too close for an adapter unless I can come up with some Offset of some kind.

 

image.thumb.png.6c533beb01735356e5e57c6eaa009bb2.png

In my repository, there are two versions of the space bar support. One which adapts to the original Mitsumi clips (preferred) and another "from scratch". You could try the "from scratch" ones. It might need some tweaking, depending on the thickness of the wire.

 

It comes in two pieces and when printing it, it's designed to be laid out thusly to increase strength in the desired directions:

 

space-clip-print-orient.jpg

 

Then you insert the sideways piece into the mount piece and clip your wire in. Again, it's a very fine tolerance type piece, so YMMV.

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@visrealm Thanks fort the pointer on the space barbut, it doesn't quite fit the bill.

Turns out the original PCB to TI attachments work fine. Maybe .5mm or so off.

The Space Bar pads, I used the original and a ockup of the ones on the original keyboard to bodge together something I think will work. It's printing right now. I had printed one I though would work and it turned out to be about 4mm too tall. I trimmed it down but now I wonder if I left enough room for the inserts. (It's always something with me.) I have a wide assortment of inserts so, I probably have something short enough to work.

image.png.7eedce397094dbfd960f58695dc95a6b.png

 

Well, while I was writing this, my test piece came off the printer. New issue. Need a hole in the center. Back to Tinkercad.

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Can anyone speculate as to whether these Cherry MX key switches would fit on the General Instrument keyboard circuit board?  The key switches on that keyboard look to be the same profile.

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14 hours ago, OLD CS1 said:

Can anyone speculate as to whether these Cherry MX key switches would fit on the General Instrument keyboard circuit board?  The key switches on that keyboard look to be the same profile.

Apparently, I don't have one of the General Instrument keyboards so I'm not much help there.. I have two with the same Keyswitches (the ones I show on the TI-99/4aW)and different keycaps (One is yellow - yes yellow not yellowed - lettering and one is white lettering). I have one of the Keyboards with a boxed in keyswitch that presses two copper plates together inside the keycap, and I had the Mitsumi which now has Cheri MX style keyswitches.

Edited by Duewester
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@visrealm  Looking forward to this!  Amazing look.  I have a box of Mitsumi membrane keyboards (Radio Shack clearance BITD) that are no use by themselves. 

 

@arcadeshopper I would go for a kit, unless you think that's a dumb idea.   If the 3D printing is a big time sink, I could have it done locally.

 

 

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10 hours ago, FarmerPotato said:

@visrealm  Looking forward to this!  Amazing look.  I have a box of Mitsumi membrane keyboards (Radio Shack clearance BITD) that are no use by themselves. 

 

@arcadeshopper I would go for a kit, unless you think that's a dumb idea.   If the 3D printing is a big time sink, I could have it done locally.

 

 

you can order with or without 3d printed parts - i haven't assembled one yet.. its in my queue

 

 

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  • 2 weeks later...
Posted (edited)

Been a while but the 99-4aW has a new keyboard with ALL functioning keys.

image.thumb.png.69623857c2de0ed29bdcc12a2484d124.png

The original KB had a Non-functioning Space Bar Keyswitch. I had swapped the Left Shift Keyswitch into the Space Bar.

image.thumb.png.a39bef6378bb5a1abf5791b8021d3902.png

Which had left this gap

image.png.db27f57c2573ebf4cbf131f15eade745.png

Thanks to the efforts of @visrealm I was able to build (so far) 3 functional Key boards. One in the Frankenine, one for the 99-4aW, a spare "Prototypeing" board.

image.thumb.png.b5c689d6ffe20b6d03620c492f5cc5d1.png

The white board had brass 1/4" keystock for stiffeners. I used brass cause, well, it's easier to drill and tap and I had some.

image.thumb.png.89459b8b5d760cc7df7834e8ff3094d2.png

I tapped it to M2 and used 8mm M2 screws and two bars not only make a stiff board, they make it feel weightier.

image.thumb.png.5dd4d986b8f75fcb2ccad0dabf43e2d0.png

Note also that I used a 90 degree header on the board to interface the wiring harness. On the prototype the wires kept breaking off when the cable flopped around while soldering in the key switches. NOTE: Hindsight - put the cable down with some VFD tape.

I used Gateron Buttery Yellow switches. They are five pi and REALLY fit the board well. So well I was tempted to not solder them in but I found that the contacts didn't always snug up against the hole sides. So I soldered them in.

image.thumb.png.2c1e1ad970a38f63b6004c8326d648ce.png

image.thumb.png.165e9fe2bd795e0d247bc6a8dba7cc03.png

The Prototype board also revealed a clearance issue

image.thumb.png.4956c1eafb190141ddc8bd6928978c0c.png

The PCB adapter needed to have more clearance on the shoulder to slide the keyboard over about 2mm. A few minutes in Tinkercad

image.thumb.png.1cd7f8df687d052ac49de67e6efaa5d2.png

and I had wider shoulder and longer holes.

The last issue was the space bar. It's different animal than the one in the Frankenine. I tried to mod the adapters in several ways and I'm just not that good. So, I modded the PCB and used two extra keyswitches.

image.thumb.png.36d331bb903cc4259e4ec382330d3add.png

Had I kept going with leftovers from the Frankenine teardown

image.thumb.png.96adbe2973b82bc8db42092645fed7d2.png

I could have this.

image.thumb.png.5e8f709edfd72cc7264bdcbf545499d5.png

At any rate, the 99-4aW Takes its' rightful place on the desk (in front of Colosus ).

image.thumb.png.b73c2445db0023f8d559742f98fa9e3c.png

OBTW - 99-4aW used the F18a Mod 1 for graphics and Frankenine uses the Tang HDMI.

Thanks for listening (Reading) and have a great weekend.

 

PS - DO NOT FORGET THE DIODE!

 

Edited by Duewester
added PS
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