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Marcel Samek · 02-21-2014, 06:48 PM

I have a Red LED version of the TI Programmer which basically looks new and untouched. It has been sitting in a drawer for years because it has such horrific key bounce issues that it is virtually unusable. Depressing a number key, for example, you will usually get anywhere from 2 to 4 of that number in the display.

I know TIs have issues with key bounce but this particular calculator takes it to the extreme which makes me think that there might actually be something wrong that could be fixed.

I have not tried to take it apart. Is there anything that can be done to improve the situation or is it a lost cause?

Thomas Radtke · 02-21-2014, 08:14 PM

I have resurrected two bouncing TI-59 keyboards and failed to do the same with a car computer (made by TI for the german market). What happened to the 59s were nearly completely dissolved spongy sheets between contacts and keys. I was successful after bathing them just once. This procedure didn't work on the car computer, unfortunately.

Maximilian Hohmann · (This post was last modified: 02-21-2014 08:41 PM by Maximilian Hohmann.)

(02-21-2014 08:14 PM)Thomas Radtke Wrote: This procedure didn't work on the car computer, unfortunately.

You mean a "LogPit"? I have two of them and both are almost unusable. But by far worst of all is a Jeppesen prostar (an aviation computer also made by TI) which is totally unusable. The keys either don't register at all or bounce so often as to fill the whole display.
So I suppose that this TI Programmer just shows average TI behavior.

Marcel Samek · 02-21-2014, 09:32 PM

(02-21-2014 08:14 PM)Thomas Radtke Wrote: What happened to the 59s were nearly completely dissolved spongy sheets between contacts and keys. I was successful after bathing them just once.

What did you bathe the sheet in?

Thomas Radtke · 02-21-2014, 10:08 PM

(02-21-2014 08:36 PM)Maximilian Hohmann Wrote: You mean a "LogPit"?

That's it.

BTW, I have an Jeppesen AvStar, based on the TI-30. Excellent keyboard as all _later_ LCD-TI's, but suffering from a zebra strip coming loose, i.e., has some segments missing. Can't they do anything right? :-(

(02-21-2014 09:32 PM)Marcel Samek Wrote: What did you bathe the sheet in?

A.dest. with some prior treatment with "Sidol Küchenkraft", the best calculator cleaner of all times ;-).

walter b · 02-21-2014, 10:20 PM

(02-21-2014 10:08 PM)Thomas Radtke Wrote:
(02-21-2014 09:32 PM)Marcel Samek Wrote: What did you bathe the sheet in?
A.dest. with some prior treatment with "Sidol Küchenkraft", the best calculator cleaner of all times ;-).

you made my day!

Paul Berger (Canada) · 02-22-2014, 12:33 AM

Bouncing keyboards where epidemic in the LED TIs of that vintage, and even some of the early LCDs. I bought a LCD programmer in hopes of escaping that blight only to find it had the same problem and upon opening it up found it had the same type of keyboard. Joerg tells me what I should get is the LCD Programmer II. I knew a guy who used to be an engineer at TI, but not in the calculator division, in the days of the red LED programmer and he told me the engineers in his area would smuggle in HP and other calculators rather than use TIs because of the bad keyboards.

Marcel Samek · 02-22-2014, 01:22 AM

Well, I opened it up and the sponge foam sheet between the buttons and keyboard mechanism was completely disintegrated. Just sticky gray dust.

I cleaned it all out with some compressed air. I searched in my garage for some suitable replacement material but could not find anything. Just as an experiment I cut a rectangle of thick felt cloth (about 1.5mm) that I had laying around and put that in there before reassembling the calculator.

It is a thousand times better than before. I still get an occasional key bounce but it is quite usable (at least for now). I'll keep my eye out for an appropriate foam on the assumption that it will work better than the felt.

Garth Wilson · 02-22-2014, 06:59 AM

I haven't seen the sheet to know how thick it should be or know what consistency it should have, but you might find something at a craft store. We use some thin foam rubber in one of our communications products made by Creatology and sold in the craft stores.

Please-- if you ever make a calculator (or anything related), put not only a decent keyboard in it, but do some proper debouncing in software too!

FWIW, I had two TI-59's and a 58c, and although their keyboards weren't perfect, they were pretty close. I know many have had problems with them though.

Thomas Radtke · 02-22-2014, 10:38 AM

(02-22-2014 01:22 AM)Marcel Samek Wrote: I cleaned it all out with some compressed air.

Ah, canned air! I should try that as well. Thanks for this tip.

(02-22-2014 01:22 AM)Marcel Samek Wrote: Just as an experiment I cut a rectangle of thick felt cloth (about 1.5mm) that I had laying around and put that in there before reassembling the calculator.

Not needed. While the keys rattle notably, they work well without any protecting sheet. Just make sure the calculator doesn't gather too much dust. For one of the TI-59s, I have a printer along with a cover(*) for this assembly. Works great.

(*) do I have to mention that this cover also shows signs of disintegration and some sewing work was in order? ;-)