is there an inner relation between the CNTRL key and both SHIFT keys on the 800XL

[newTIboyRob]

About a month ago, I made a post with some photos of my 800xl that was working fine with the exception of its printing of the symbols above the number keys. That post was called "characters above # keys print out though Shift Key Is Up."  I mention it so as to give you some background and the keyboard's actual photos. You will see that I got as far as opening her up... but then closing her up.

 

In the interim, I have been working across other computer platforms in search of other programs and the like, but I actually found someone who will do this 800XL repair for me, which is great! So this post, though related, is just a little different, as it is more theory-based-behind information I am hoping to be explained now. 

 

So again, please note: I am NOT looking for someone to, or how do I fix this problem in this thread;  I'm just a little curious if you can point out if there's a common denominator with what's going on here, or at least some thoughts/theories:

 

I ran the diagnostic keyboard test today and learned that actually 3 keys, CNTRL and both SHIFTS all do not work, as I don't hear them when pressed on the test.  Pressing the number keys only prints the symbols above, no numbers, and luckily that's the only issue here, but it still needs to be addressed if I want to type in any programs.

 

So the question: In just simple, layman's, as least-technical-as-you-can-put-it-if-possible terms, do those 3 particular keys all share anything in common?  I recall there was an inner keyboard diagnostic photo that had been posted several times on the forum, so perhaps someone could repost it here with an explanation?  For example, do the 2 shift keys share the same path (is that called a trace?) which could mean that whole path is out?  Does it means it would need a new mylar or whatever it's called (you can see I am not term-solid)  Show me if the CNTRL key is related to those other 2 keys path-wise, or does it take a different inner route, that kind of thing.

 

Again, I am just curious here to know what the tech will be looking for as he navigates in there... if someone could explain what they think might be, or even is likely going on with those 3 particular keys, if such an explanation could even be determined from just the photos and issue here? 

 

 

 

[Beeblebrox]

Can you link to the original post or repost those images as I cannot find the old post you reference.

 

Would be good to see which keyboard you have again as there are several different 800XL types (mylar/membrane OR mechnical). We'd need to see the underside of the keyboard to see.

 

If it's a mylar/menbrane type there are linked matrixes between certain keys, so if there is a crack/defect in one of the mylar/membranes tracks they share, they can all go.

 

For example for illustrative purposes only as it's to hand here is a mylar/membrane I worked on/fixed for a mitsumi 1200XL keyboard, where you can see I mapped out things whilst fixing it last year, as I slowly brought keys back that weren't functioning:

 

 

You can take from this that certain keys will all get knocked out if a shared track/path is deffective.

 

As I say, link to the original post with the pics of your keyboard, or repost those images so we know which keyboard you have.

[newTIboyRob]

It may sound silly, but I don't know how to do that with the links I mean.  It is on page 5, August 16. I will try again with the photos if you can't find...

 

Edited September 7, 2023 by newTIboyRob

[newTIboyRob]

Here were 2:

 

[Beeblebrox]

I still couldn't find your original post and thanks for the pics but unfortunately we need the inside of the computer - the underside/back of the keyboard, to see if it's a mechanical one or a mylar/membrane.

 

Open it up, snap a pic and post it.

 

I am guessing it's going to be a mechanical but can't be sure.#

 

PS to share a post:

 

 

then copy the url into another post:

 

 

 

EDIT:

 

Also, once we know which keyboard you have also see this post. 2nd or third reply down there is a keyboard matrix diagram mapping out the connections:

 

 

Edited September 7, 2023 by Beeblebrox

[TGB1718]

1 hour ago, newTIboyRob said:

I ran the diagnostic keyboard test today and learned that actually 3 keys, CNTRL and both SHIFTS all do not work, as I don't hear them when pressed on the test. 

On their own, they do not make a noise or register on the display, to see if they work, you press

SHIFT or CNTL and any key to see the operation, you should hear a beep and the display

highlights the SHIFT/CNTL key and the key you pressed.

 

In terms of the circuit board is concerned, both shift keys are connected to the same pin on the

keyboard interface, however depending on the mylar used, they both may take different paths

and join up at the interface connector.

[Rybags]

The keyboard matrix diagram gives a clue.  Often if keys are on the same row or column, a fault in one can be present on the others.

Break, Ctrl and Shift share a column.

Also, there's no way to distinguish between the Shift keys.

[newTIboyRob]

 

All 3 posts above were terrific, thanks. Ah, Beeble... I saw the "Share" option above right which connected to the other platforms and proceeded to head for the hills!  (Didn't know the share thing here was embedded in those 3 tiny dots. Who woulda thunk it?)

 

 Any hoo... above is the fruits of your teaching       You believe it to be a membrane/mylar type....

 

 

Edited September 7, 2023 by newTIboyRob

[+CharlieChaplin]

A program (or the computer) cannot detect if the left or right Shift key has been pressed.

But it is possible to detect a pressed/hold-down Shift key without any other key (Shift key only).

Afaik, it is not possible to detect a pressed/hold-down Control key without any other key (Control key only).

 

[newTIboyRob]

Hmm.. from above,  you say BREAK, CNTRL and SHIFT share a column... This is now getting even more interesting, (well at least to me). I went back to the Keyboard test. TGB1718's mention was also vital here. I went back and pressed every key.

 

1) Turns out that both SHIFT keys actually DO work. (If I could have easily changed the title/s of these thread/s I would have.)  When I pressed the number keys by themselves, they all worked, and when I pressed either Shift key with the number keys, they all beeped.

 

2) Ok, so the CNTRL key doesn't make a sound by itself when pressed. So I pressed and held that key down while then pressing each key, rhythmically through all the keys, and there were no beeps.

 

3) the BREAK key also is not supposed to make a sound when pressed by itself on that test, correct?  I did try pressing it by itself... no beep. I tried, just for giggles, pressing and holding it while pressing other keys... no beep.

 

Thinking out loud here... So this tells us something is awry with that column then? Does it get replaced or altered? Maybe it's not as simple as that, if all the paths go in different directions before their destination at the interface connector?

 

So is this all a game of "test and first find the path"?   (Maybe it's not as simple as that either, which is why I need a tech for this repair.)

I am clueless here, but if you were the tech, what would your approach be? 

 

 

Edited September 7, 2023 by newTIboyRob

[+x=usr(1536)]

23 minutes ago, newTIboyRob said:

3) the BREAK key also is not supposed to make a sound when pressed by itself on that test, correct?  I did try pressing it by itself... no beep. I tried, just for giggles, pressing and holding it while pressing other keys... no beep.

Correct: it should not flash (or beep).

[Rybags]

Self Test Keyboard test only reads the keycode register.

Break isn't covered I don't think in any version.  Also, Break keypress only generates an IRQ at key down condition, there's no way to tell if it's held down or when it's released (possibly disable/re-enable keyscan could, not sure on that)

Shift/Ctrl only show if in conjunction with a printable key.

CTRL on Atari can not be detected when it's the only keypress.

Edited September 8, 2023 by Rybags

[newTIboyRob]

So the consensus is that CTRL can not be detected when it's the only key pressed by itself.  But... is it supposed to light up and beep on the test screen if used with/when another key is pressed shortly thereafter, (like a CNTRL-P for print concept for example.)

 

(Thus, if it didn't light up or beep on the screen during the test when used in this way, can we consider it broken?)

Edited September 8, 2023 by newTIboyRob

[mimo]

4 hours ago, newTIboyRob said:

So the consensus is that CTRL can not be detected when it's the only key pressed by itself.  But... is it supposed to light up and beep on the test screen if used with/when another key is pressed shortly thereafter, (like a CNTRL-P for print concept for example.)

 

(Thus, if it didn't light up or beep on the screen during the test when used in this way, can we consider it broken?)

Yes

[newTIboyRob]

That's what I thought, ok thanks. The plot thickens.

[TGB1718]

Generally the sort of problem you have suggests a good clean of the mylar and key pads, I've

had random key problems on one of my XE's over the years (really need to get a new mylar)

and a good clean usually does the trick.

[newTIboyRob]

Ok, makes total sense. What does a new mylar, in general, cost in the US?