Mylar Type Keyboard repair?

[Markeno]

I was wondering if anyone knows of a way to repair the mylar type keyboards.  The keys work, but many don't work well.  Many take alot of pressure.  But also many type multipule keys even with a very quick press.  Is that that also the keyboard itself?

 

[+arcadeshopper]

I was wondering if anyone knows of a way to repair the mylar type keyboards.  The keys work, but many don't work well.  Many take alot of pressure.  But also many type multipule keys even with a very quick press.  Is that that also the keyboard itself?
 

This is covered in the pinned FAQ

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[Ed in SoDak]

Repair by replacement with one of the better-made keyboards. I don't think there's a fix worth trying, such as cleaning or conductive paints, etc. Lot of work with no long-lasting effect and might make it worse or no better afterwards. Easier to just plunk in a working one. Use care with the connector, they can be fragile as well.

-Ed

[Markeno]

I should have noted that I have seen the Mylar fix post.  I was not impressed with the likelihood of a fix, or at least a long term one.  I haven't heard of any of the old vintage Mylar keyboards being properly repairable.   I wanted to see if there was some reliable method found here.  I'll likely attempt it at some point, but I am not expecting amazing long term results.

 

I am not yet happy enough with the 99/4a to invest another likely $75.00 to hope to get a good Alps keyboard, or least one that is repairable.  I was very disappointed to find this unit had the Mitsumi.  It is sad that it is so similar to the Commodore 64, except spring placement and being membrane.  I would almost design a pcb replacement, except the stems don't have the conductive pads on the bottom, and the springs are setup differently and wouldn't work.

 

From what I read, I take it the multi keystrokes are likely "poor" condition contacts barely making contact, and sort of making it like it is bouncing?  Being wired directly to the cpu inputs, it shouldn't be a circuity issue then?

 

 

[+OLD CS1]

2 hours ago, Markeno said:

I am not yet happy enough with the 99/4a to invest another likely $75.00 to hope to get a good Alps keyboard, or least one that is repairable.  I was very disappointed to find this unit had the Mitsumi.

Bad luck of the draw.  You should, however, be able to find someone who has a non-Mitsumi to sell relatively inexpensively.  Unfortuantely, I exhausted my stock a while back.

2 hours ago, Markeno said:

Being wired directly to the cpu inputs, it shouldn't be a circuity issue then?

Technically, the keyboard is not wired to the CPU but the 9901.  Otherwise, no, not likely a circuitry problem.  I have heard of 9901s going bad, but it seems to be rare.

[Ed in SoDak]

Most likely just Mitsumi at fault. I've never seen console-related key-input issues, always been the keyboard. The other types can get dirty or break a solder joint, but at least that's easily dealt with.

 

You could jumper the keyboard connector at those points to check the motherboard side of things. Touch the jumper to the second contact and pretend you're the keyswitch. Such fun! Or a DMM on Ohms should show the contact failing/making/failing... and you wouldn't need to power up the disassembled console to test.

 

For some years after TI bowed out, you could find good Alps keyboards in surplus for $5 each. I picked up a few back then. If I still have any left, they're buried in the shed somewhere and may be the duds I pulled and replaced. Too long ago now to remember.

 

But somebody on here has gotta have a stash, ya'd think. Or hunt down a non-working console with an Alps. I've sold a couple like this for cheap where the known good keyboard was the best part of the deal.

 

Arcade Shopper sells a USB adapter, also you could roll the dice for another Mitsumi which he offers as-is and hope to get a working one. My luck is never that good.

 

https://www.arcadeshopper.com/wp/store/#!/Keyboards-and-adapters/c/23836460

 

The key matrix isn't that hard to figure out with a schematic on hand. I repurposed a couple for use on my Timex TS1000 by cutting some board traces and adding some flying leads.

[Markeno]

I am the most tempted by coming up with a replacement board, switching it over to some microswitches.  It has been a month or more since I pulled the keyboard apart, I am not sure if it would be practical to attempt that.  

 

The USB adapter there is to setup input to the TI from a modern usb keyboard then?  Indicating even a wireless one.  I would rather have a working keyboard on the computer if I can.  I will keep an eye out for an Alps keyboard.  It seems though they have what is called a "Stackpole" keyboard, I am seeing a number of 99/4as for sale with a missing key or so which are of that type.  It doesn't sound like they are a great design either.  I am not sure how I would reliablly be able to tell between it and the Alps model on an ebay listing.  That is short of finding an Alps that is obviously broken, then I would need another for some switches for parts..  Seems like a bit of a mess.

[+Ksarul]

The Stackpole keyboards are actually quite reliable--and it is a snap to clean the contacts in them if they do get dirty and start to double trip or not trip at all. If you find one with all the key caps, it will last a very long time. . .

[+arcadeshopper]

I am the most tempted by coming up with a replacement board, switching it over to some microswitches.  It has been a month or more since I pulled the keyboard apart, I am not sure if it would be practical to attempt that.  
 
The USB adapter there is to setup input to the TI from a modern usb keyboard then?  Indicating even a wireless one.  I would rather have a working keyboard on the computer if I can.  I will keep an eye out for an Alps keyboard.  It seems though they have what is called a "Stackpole" keyboard, I am seeing a number of 99/4as for sale with a missing key or so which are of that type.  It doesn't sound like they are a great design either.  I am not sure how I would reliablly be able to tell between it and the Alps model on an ebay listing.  That is short of finding an Alps that is obviously broken, then I would need another for some switches for parts..  Seems like a bit of a mess.

Usb is standard usb keyboard interface yes it works fine with wireless keyboards

More info here: https://www.jedimatt42.com/ti99usbkeys.html

I sell blank pcb and also assembled adapters at arcadeshopper.com look under ti hardware and keyboard

Greg


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[Markeno]

That adapter is a cool project.  It is something to think about.  

 

I just ordered a 99/4a for what I figured was near reasonable.  It doesn't have a Mitsumi keyboard, and looks to be complete.  I am still tempted to see if I can actually make a replacement board for the Mitsumi.  I have enough other projects that I know are within my abilities though to keep me busy though.

[Omega-TI]

With all the modern projects for the TI that have come out in the last few years, I'm kinda surprised a new PCB has not appeared on the scene for a replacement.  Then again, it's probably due to the keytops and price being the Achilles heel.

 

One with light up keytops would be real cool!

 

[Markeno]

Well the market isn't big enough to get a commercial keyboard producer interested.  I am just thinking it may be possible to retrofit the Mitsumi style keyboard with a board with tactile switches.  The matrix as mentioned is nothing complex, it is about getting the switches in there, and the key stems being able to reliably press them.  I don't know if those issues could be solved reasonably if at all.

[+arcadeshopper]

Easier to just design a new keyboard with good switches and drop it in like the tomy and coco ones that have been made..

 

But then I'm not up to designing it so I'm not expecting anybody else to do it.

 

And yeah the key tops are the hardest part since they're unique

 

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[Ed in SoDak]

There's new replacement membranes made to fit the Sinclair Spectrum, ZX81 and Timex TS1000 and TS1500. Good thing, since the original membrane is pretty much doomed to fail at some point and nearly all the different models used them.

The replacements are well made, sold out of the UK and cost with mailing is reasonable. I paid around $24 for one to fit my TS1500. It's a three-layer sandwich; two contact layers with a separator between, with many punched alignment holes. Less likely than the Mitsumi to get dirt on the contacts since the layers are sealed together.

 

For the TI99/4A, a Mitsumi membrane would require just a single layer with a separator since the circuit board provides the second contact "layer." Installation would likely be more involved.

 

No doubt the market for such things is larger for the still-popular Sinclair family. On the TI, only a percentage of consoles have a Mitsumi. Since so many consoles were sold in total and most had better keyboards, it has been "easy enough" to either avoid the Mitsumi variant or deal with it by finding another TI or better keyboard when one goes bad. That's getting harder to do affordably as time goes on.

 

Maybe the folks who produce the Sinclair membranes could be approached with the idea.

-Ed

Edited December 2, 2020 by Ed in SoDak

[Count9929A]

8 hours ago, Ed in SoDak said:

There's new replacement membranes made to fit the Sinclair Spectrum, ZX81 and Timex TS1000 and TS1500. Good thing, since the original membrane is pretty much doomed to fail at some point and nearly all the different models used them.

 

[CUT]

No doubt the market for such things is larger for the still-popular Sinclair family. On the TI, only a percentage of consoles have a Mitsumi. Since so many consoles were sold in total and most had better keyboards, it has been "easy enough" to either avoid the Mitsumi variant or deal with it by finding another TI or better keyboard when one goes bad. That's getting harder to do affordably as time goes on.

 

Maybe the folks who produce the Sinclair membranes could be approached with the idea.

-Ed

 

Here they have replacement membranes for many computers (atari 800, various Amigas, etc.). Even for machines like Elan Enterprise that IMHO are less popular than the TI

 

[Ed in SoDak]

5 hours ago, Count9929A said:

 

Here they have replacement membranes for many computers (atari 800, various Amigas, etc.). Even for machines like Elan Enterprise that IMHO are less popular than the TI

 

Thanks for the link, that's the place I was referring to and ordered from. Maybe it's worth a shot seeing if they'd add the Mitsumi.

-Ed

[Ed in SoDak]

Ahhh, 1985 and after... those were the days for those of us into the recently orphaned TI99 when the bits and bobs started to show up cheap in the surplus electronics catalogs and ads, then later on low buck PC floppy drives, etc...

 

 

[Markeno]

I would think the easiest solution would be if someone were to make a new membrane.  There are obviously people there that know how to reproduce good replacements for those kinds of keyboards.  The process I believe ends up getting the mylar correct then they silk screen the traces on right?  No modification, and in theory a reasonable cost.  I did buy one of the new ones for a Z81 for my Timex Sinclair 1000.  Although I haven't yet had to swap it out, the original is still working so far, although I haven't used it much.

 

It would be quite an involved process to get a full new keyboard designed and manufactured.  I expect it would be out of the casual enthusiast interest due to cost though.  Still for some who really are into them, I could see a wider interest due to their Alps or Stackpole etc keyboards being worn, or missing components etc.

 

Either of those options are well out of my area of expertise.  I will probably try something with the Mitsumi one I have to get it into a usable condition, but I don't know what that may look like in the end.

Edited December 3, 2020 by Markeno

[+arcadeshopper]

There's also the fact that if you make a membrane keyboard replacement membrane it's just going to go bad sooner or later leaving you in the same boat that you're in now

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[Omega-TI]

16 minutes ago, arcadeshopper said:

There's also the fact that if you make a membrane keyboard replacement membrane it's just going to go bad sooner or later leaving you in the same boat that you're in now

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This may be true, but considering how long they took to self destruct the first time, many of us here will already be dead when that happens.

[+arcadeshopper]

That may be true but new in the box mitsumi keyboards never used are already bad with no use

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[HOME AUTOMATION]

42 minutes ago, Omega-TI said:

many of us here will already be dead when that happens.

...True, maybe. Still, a tough conceit to swallow!

[Omega-TI]

5 minutes ago, arcadeshopper said:

That may be true but new in the box mitsumi keyboards never used are already bad with no use

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Yeah, but they are at least 37 years old.  I dunno about you, but I know I have less than that ahead of me.

[Omega-TI]

1 minute ago, HOME AUTOMATION said:

...True, maybe. Still, a tough conceit to swallow!

 

Yeah, calculating the average lifespan of all my dead direct relatives, I figure I have between 15-26 years left at most.

[Ed in SoDak]

A toast then, to us and the TI

 

While we yet live

  Let us live in clover

    For when we're dead

      We're dead all over