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TI 99/4a Keyboard and mainboard


Sinphaltimus
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I took a risk and purchased a console only as is untested. It was under 25 bux including shipping.

It seems fully functional except the keyboard. I replaced it with a partially working keyboard to check.

First time seeing one and I have to ask, are those blue wires from the factory or had this been modded in some way?



So I'm still hunting for a kb.post-47352-0-90779400-1474318666_thumb.jpg

Edited by Sinphaltimus
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My adventure continues. I changed the topic to reflect where we are going from here....

I have 2 brand new and never used radio shack replacement keyboards from the era that I was told do not work at all.

Never used? OK, just once I suppose.

Anyway, I figured with nothing to lose, why not take one apart and see if there isn't something I could do.

Here it is, top and bottom.

post-47352-0-70594100-1474322398_thumb.jpgpost-47352-0-47433900-1474322454_thumb.jpg

And this thing looks like its in pretty good shape. Let's try this out alone before anything more.

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And it works. I ended up testing all the keys and they all work. (sorry for the side ways) Hrm... What's with the actual keys?

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I don't know. Everything looks great. It must be that the membrane is a little stiff and the keys can't produce the pressure needed.

post-47352-0-06594500-1474322573_thumb.jpg

These things look great and feel great as well. Hrm.. What the heck? OK, I have an idea.

 

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First, I'm going to put it all back together again and see if it works. don't roll your eyes or shrug or laugh, this is a proven method. I can't tell you hopw many things I've fixed just by taking them apart and putting them back together. i can't explain it so that's what I'm going to do next. I'll report back.

oh and for the record, I'm thinking of little knobs of hot glue as a replacement for those soft nubs or to at least add to them. We'll see how the next step turns out first. I might have a good keyboard repair mod coming soo. Being discovered as I post this.

 

EDIT: Nope. Time to heat up the glue gun...

Edited by Sinphaltimus
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LMAO! I suppose I opened a can of worms....

Well, it's not over....

 

So I didn't want to damage the board, I mean it works.. Cover it in plastic. This was the best I could find on short notice.

This part sucked.

post-47352-0-62676400-1474326427_thumb.jpg

 

Took a while...
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Let's put a few screws in to hold everything in place.
post-47352-0-58853700-1474326304_thumb.jpg

 

post-47352-0-26576800-1474326352_thumb.jpg

Well. I managed to get a few keys to respond but not good enough. I think my approach is sound but I am lacking the proper materials. I need a sheet of plastic rigid enough to hold its shape but flexible. Much like the membrane itself. The keypad and membrane all work great. It's the physical keys that aren't applying enough pressure from what I can tell. I want to give them a spacer so to speak.

 

Once I find the kind of sheet I'm looking for, I will revisit this. Until then, we'll have some fun iwth the comments. I love Iron Maiden. Thanks for that. :)

 

post-47352-0-14381500-1474326394_thumb.jpg


Other ideas. I may try to add hot glue knobs to the ends of the physical keys. but I don't want to damage anything so I need to figure out a way to keep all parts in tact, just modified with the hot glue. The little silicone tips are really soft and not at all applying enough pressure from what I can tell when I press the board with my fingers.

Edited by Sinphaltimus
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WHOA!

I decided to take it apart a little further by separating the membrane from the PCB. I was thinking, "what if it's not the keys but the membrane3 is shorted or something?"

post-47352-0-36329600-1474327462_thumb.jpg

A quick test with only one screw in AND IT WORKS!!!!

HOLY COW!

post-47352-0-98409100-1474327405_thumb.jpg

 

OK, Now to put the console back together and test again. :)

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I now have my SECOND fully functional console!

This is going to be my modding machine. I will be giving it the internal 32k mod this weekend I hope. Depends on what other parts come in for other projects.

 

post-47352-0-16845500-1474330190_thumb.jpg

Now if I can get this other keyboard (the twin) working using the same method, I'll have a third console up and running in no time. But not tonight. Tired, bedtime. More tomorrow!

Whoot!

This is great. :)

 

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ohhh yeah !! :D , i fixed 5 on 6 of them in August, Membrane was the cause

 

post-24673-0-90140100-1474354154_thumb.jpg
https://www.facebook.com/groups/ti99iuc/permalink/1267913656582698/

 

the last one now just missing a key :P i am preparing a little step by step guide but just few free time in the last days.

 

i also used the conductive silver ink for repair

 

post-24673-0-89984800-1474354505_thumb.jpg post-24673-0-02992400-1474354524_thumb.jpg post-24673-0-96967700-1474354537_thumb.jpg

 

i suggest anyway to be careful not to detach the part of the main contacts

 

post-24673-0-12834500-1474354739_thumb.jpg

Edited by ti99iuc
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Well, I'm going to do it again. I have another console and the exact same keyboard (new used once). So I do plan to do this again, from start to finish

 

I can take better pictures, more pictures, and document better than real-time seat of my pants.

 

I can have that done by Sunday.

 

I might even get the internal 32k mod, high speed console mod and reset button mod all completed and documented this weekend. We'll see. Mitsumi keyboard for certain.

Edited by Sinphaltimus
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Well, I'm going to do it again. I have another console and the exact same keyboard (new used once). So I do plan to do this again, from start to finish

 

 

Excellent! Thank you. :thumbsup:

 

As a community, the TI group here at Atari Age has a large percentage of people with in-depth knowledge about every aspect of the machine and it's peripherals. If anyone can preserve the posterity of the TI, it's this group here. And time IS of the essence because some of the best names in the TI community have already passed on, and sadly we continue lose others, so preserving their knowledge, as well as preserving the knowledge of how to maintain the TI is paramount.

 

A document on how to restore the keyboard WILL save uncounted otherwise working TI's from the garbage bin, elevate their worth, and at the very least insure a larger supply of repair parts.

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The quick of it. I took it apart and put it back together after separating the white membrane from the pc board.

 

That's really all I did.

 

The caveat is this. These mitsumi keyboards I have were never used. They were purchased new from radio shack by the previous owner and stored away ever since.

 

When the previous owner went to use his TI after years in storage, the keyboard didn't work. He tried both mitsumi keyboards for the first time and neither worked.

 

They didn't have any wear and tear which I'm guessing your box of keyboards do have.

 

The entire membrane of mine was just stuck to the pc board.

 

I don't think what I did will work on others that maybe worn out or damaged in some way but I suppose it's with a shot?

Edited by Sinphaltimus
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They didn't have any wear and tear which I'm guessing your box of keyboards do have.

 

 

"NOS" stands for "New Old Stock"... it means they are unused and stored for a really long time. ;)

 

Ah, so your suspicion is just that they are shorting out, and splitting it apart gets them working again? That's not a bad theory, I'll give one a try.

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So.... success! I had never attempted this before because I thought it was /supposed/ to be glued to the PCB, but I took a new one out of the box and tested it - maybe 4 keys worked. I took it apart, peeled off the plastic sheet (per your notes that I read somewhere, I didn't unstick where the sheet connected electrically to the PCB, but I ensured all keys were unstuck), put it back together, and every key works! A couple are a little stiff, no different than any of the fully-mechanical switch keyboards, and should come up with a little use (or better, just clean the contacts while you have the sheet up).

 

This is rather good news, actually, since the failure of these keyboards has been a major complaint for many of us for a lot of years now. ;) I feel a bit better about them!

 

Only three gotchas I saw... lots of screws (15), it's a pain. And be gentle unsticking the plastic sheet, as it can tear. (I got a small tear near one of the holes, fortunately it did not impact any traces). Finally, you have to desolder the Alpha Lock key to get it apart. (easy, but a gotcha.)

 

(Edit: added alpha lock gotcha)

Edited by Tursi
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Yeah, I didn't mention the alpha lock, i wasn't aware I'm probably one of the only folks to bother taking one apart completely.

I agree, too many damn screws.

I'm very happy this worked for you.

Now I'm really excited to do the new and improved PDF with a video to go with it. :)

EDIT: I completely removed the membrane with no regard for the contact points for the board. I didn't know and it didn't seem to make a difference.

Edited by Sinphaltimus
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Now I'm really excited to do the new and improved PDF with a video to go with it. :)

 

 

Really looking forward to this. Websites can come and go, PDF's can live on and are easily sent to someone in need.

 

There are also some really good threads here on Atari Age that could be mined and turned into PDF's as well. Mainbyte has some neat projects that can easily be copied & pasted into Word and saved as a PDF as well with minor tweaking and proper attribution.

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Yeah, Mainbyte is a great resource. There are a lot of projects all over the place. I think Shift's site is the only place I ever found anything about the reset button mod. Never knew it existed until I decided to visit the sites of some members. And I always "Print to PDF" for personal storage.

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Yeah, Mainbyte is a great resource. There are a lot of projects all over the place. I think Shift's site is the only place I ever found anything about the reset button mod. Never knew it existed until I decided to visit the sites of some members. And I always "Print to PDF" for personal storage.

 

I've done that on occasion myself (see attachment) ;)

PEB 12 volt 2 Amp Power Upgrade.pdf

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