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Osborne 1 keyboard interface?
- Thread starter NutmegCT
- Start date
daver2
10k Member
Yep, this fault is a doozy!
I have a few more ideas now I have had a think overnight. But I agree with VERAULT - let's have a couple of days off to recuperate and have another crack at it shortly. How does that sound to you?
Dave
I have a few more ideas now I have had a think overnight. But I agree with VERAULT - let's have a couple of days off to recuperate and have another crack at it shortly. How does that sound to you?
Dave
NutmegCT
Experienced Member
Agreed!
daver2
10k Member
Give me a couple of days (another business trip coming up) and I will post my thoughts on what I think the issue could be.
When you are ready to have another go we can proceed from there.
Dave
When you are ready to have another go we can proceed from there.
Dave
NutmegCT
Experienced Member
OK - just post your thoughts when you get back and we'll start anew.
My thought: both keyboards are toast and I need to find another.
Tom M.
My thought: both keyboards are toast and I need to find another.
Tom M.
NutmegCT
Experienced Member
I wonder if Daver2 is back.
I'd like to hear those fresh thoughts mentioned in Post #64!
Tom M.
I'd like to hear those fresh thoughts mentioned in Post #64!
Tom M.
daver2
10k Member
The quick answer - I will expand a bit later - is twofold:
1) Some of the signals are not true digital signals and have degraded such that the voltage levels lie within the 'grey' area of the TTL range. Not too high to be consistently seen as a logic '1' and not too low to be consistently seen as a logic '0'. Unfortunately, with TTL logic, the middle ground is absolutely no good!
2) The shielding is ineffective.
In both cases I can see why the keyboard may just work on one machine and not on the other.
The possibility for a fault occuring between testing the keyboard itself with your multimeter and re-testing it with the cable attached may just be the resistance range I chose for the latter test. I wanted to see whether there was any resistance in any of the key matrix keys rather than looking for just a low resistance.
I will expand on these when I get home from work and I have a little bit of spare time to do so.
Dave
1) Some of the signals are not true digital signals and have degraded such that the voltage levels lie within the 'grey' area of the TTL range. Not too high to be consistently seen as a logic '1' and not too low to be consistently seen as a logic '0'. Unfortunately, with TTL logic, the middle ground is absolutely no good!
2) The shielding is ineffective.
In both cases I can see why the keyboard may just work on one machine and not on the other.
The possibility for a fault occuring between testing the keyboard itself with your multimeter and re-testing it with the cable attached may just be the resistance range I chose for the latter test. I wanted to see whether there was any resistance in any of the key matrix keys rather than looking for just a low resistance.
I will expand on these when I get home from work and I have a little bit of spare time to do so.
Dave
daver2
10k Member
Do you want to continue with this or are you going to go down the route of replacing the keyboard with something else?
I have two weeks 'spare' before I start my business trips again.
I would like to repeat the voltage measurements around the 20 pin buffer related to reading the keyboard (I can get you the IC reference later). First, without the keyboard connected and second with your replacement keyboard attached but with no keys pressed. This is the device where 'strange things' occurred when you measured a couple of the pins.
I would also like you to remeasure the key matrix on the keyboard (both with and without the keyboard cable connected to the keyboard - but not with it connected to the O1). The multimeter should be set to measure resistance with a 20 kOhm (or so) maximum scale. All lines of the row and column should be a very high resistance when the keys are not pressed. Any 'lowish' resistance reading when the key is not pressed could compromise the reading electronics. In this case, I would like to know what the resistance reading is.
The above is an overview; so I can expand on my description as required.
Dave
I have two weeks 'spare' before I start my business trips again.
I would like to repeat the voltage measurements around the 20 pin buffer related to reading the keyboard (I can get you the IC reference later). First, without the keyboard connected and second with your replacement keyboard attached but with no keys pressed. This is the device where 'strange things' occurred when you measured a couple of the pins.
I would also like you to remeasure the key matrix on the keyboard (both with and without the keyboard cable connected to the keyboard - but not with it connected to the O1). The multimeter should be set to measure resistance with a 20 kOhm (or so) maximum scale. All lines of the row and column should be a very high resistance when the keys are not pressed. Any 'lowish' resistance reading when the key is not pressed could compromise the reading electronics. In this case, I would like to know what the resistance reading is.
The above is an overview; so I can expand on my description as required.
Dave
NutmegCT
Experienced Member
Thanks Dave.
Before I dive back into the abyss ...
(1) if we do indeed find a problem on the main logic board itself, how would that be repaired? I've tried logic board repairs on other devices, which only resulted in my damaging the boards further.
and
(2) if we find another problem on the keyboard(s), how would those be repaired? There are many references to irreparable matrix failures in various posts.
I don't have a problem continuing the multimeter diagnosis procedures, but it seems we're doing autopsies, with little possibility of resurrections.
Tom M.
Before I dive back into the abyss ...
(1) if we do indeed find a problem on the main logic board itself, how would that be repaired? I've tried logic board repairs on other devices, which only resulted in my damaging the boards further.
and
(2) if we find another problem on the keyboard(s), how would those be repaired? There are many references to irreparable matrix failures in various posts.
I don't have a problem continuing the multimeter diagnosis procedures, but it seems we're doing autopsies, with little possibility of resurrections.
Tom M.
daver2
10k Member
>>> but it seems we're doing autopsies, with little possibility of resurrections.
To carry on with the medical analogy - I think the patient is still in the medical centre being diagnosed as to what the problem is. Once we have a diagnosis, then we can treat the problem - not before.
We still don't know where the problem is - and this (to me) sounds like a not-so-simple fault. It may turn out to be a simple fault that is presenting in a weird way. We just don't know...
If it transpires it is on the main logic board - then you have a couple of possibilities: (1) learn the skills yourself to replace an IC. If you know the correct way to replace an IC (we can explain this to you), and have the right tools (most of which are relatively cheap), and have practiced on some 'gash' stuff that you can purchase from e-bay then you may decide to attempt the repair yourself. (2) find someone locally with the right skill set. TV/audio equipment repairers, local computer enthusiasts with the right skill set - or even a local VCFED member willing to help out. (3) send it away for repair (now you know definitively what the problem is).
Besides which - if the problem is on the main logic board, then obtaining a keyboard replacement (be it a real keyboard or something 'faking' the keyboard) is going to be counter productive as the actual problem is elsewhere.
If we know for absolute sure that the replacement keyboard you have obtained is also faulty - then you either need to learn from that in the next one you purchase, or look to get a 'virtual replacement' as you have asked in another thread. This, in itself, will be an interesting project for someone to take on - but whether it will actually fix your problem...
Faced with what you are I would proceed as follows:
(1) Connect the keyboard cable up to the O1.
(2) Leave the physical keyboard disconnected from the keyboard cable.
(3) Boot up CP/M on the O1 by 'faking' the <RETURN> key (as you have done previously by shorting out the row and column corresponding to the position of the <RETURN> key in the key matrix).
(4) Thoroughly test every single key in the keyboard matrix by shorting out the key on the row/column at the keyboard end of the keyboard cable and ensuring the O1 displays the correct corresponding character (or performs the appropriate action if it is a control key).
If the above works OK - there would seem to me to be no logic fault present on the main logic board of the O1 or in the keyboard cable itself. What we are then left with is the replacement keyboard you obtained - or electrical shielding (which is what I think the missing pin on the keyboard connector of the O1 is concerned with). If it is the electrical shielding - this may turn out to be a bi*ch of a fault with a simple fix...
Dave
To carry on with the medical analogy - I think the patient is still in the medical centre being diagnosed as to what the problem is. Once we have a diagnosis, then we can treat the problem - not before.
We still don't know where the problem is - and this (to me) sounds like a not-so-simple fault. It may turn out to be a simple fault that is presenting in a weird way. We just don't know...
If it transpires it is on the main logic board - then you have a couple of possibilities: (1) learn the skills yourself to replace an IC. If you know the correct way to replace an IC (we can explain this to you), and have the right tools (most of which are relatively cheap), and have practiced on some 'gash' stuff that you can purchase from e-bay then you may decide to attempt the repair yourself. (2) find someone locally with the right skill set. TV/audio equipment repairers, local computer enthusiasts with the right skill set - or even a local VCFED member willing to help out. (3) send it away for repair (now you know definitively what the problem is).
Besides which - if the problem is on the main logic board, then obtaining a keyboard replacement (be it a real keyboard or something 'faking' the keyboard) is going to be counter productive as the actual problem is elsewhere.
If we know for absolute sure that the replacement keyboard you have obtained is also faulty - then you either need to learn from that in the next one you purchase, or look to get a 'virtual replacement' as you have asked in another thread. This, in itself, will be an interesting project for someone to take on - but whether it will actually fix your problem...
Faced with what you are I would proceed as follows:
(1) Connect the keyboard cable up to the O1.
(2) Leave the physical keyboard disconnected from the keyboard cable.
(3) Boot up CP/M on the O1 by 'faking' the <RETURN> key (as you have done previously by shorting out the row and column corresponding to the position of the <RETURN> key in the key matrix).
(4) Thoroughly test every single key in the keyboard matrix by shorting out the key on the row/column at the keyboard end of the keyboard cable and ensuring the O1 displays the correct corresponding character (or performs the appropriate action if it is a control key).
If the above works OK - there would seem to me to be no logic fault present on the main logic board of the O1 or in the keyboard cable itself. What we are then left with is the replacement keyboard you obtained - or electrical shielding (which is what I think the missing pin on the keyboard connector of the O1 is concerned with). If it is the electrical shielding - this may turn out to be a bi*ch of a fault with a simple fix...
Dave
Last edited:
NutmegCT
Experienced Member
Thanks. I'll tackle these tests during the week. Learn something new every day, for sure.
Tom M.
Tom M.
NutmegCT
Experienced Member
Status report:
With cable in logic board socket, but no keyboard attached - pin (socket) combinations work properly.
With same setup, but *newer* (replacement) keyboard attached (no keys pressed) - screen is immediately filled with "ttttttttttttttttttttttttt" etc. until keyboard is disconnected.
With same setup, but original keyboard attached (no keys pressed) - screen is immediately filled with "54545454" etc. until keyboard is disconnected.
With cable in logic board socket, but no keyboard attached - pin (socket) combinations work properly.
With same setup, but *newer* (replacement) keyboard attached (no keys pressed) - screen is immediately filled with "ttttttttttttttttttttttttt" etc. until keyboard is disconnected.
With same setup, but original keyboard attached (no keys pressed) - screen is immediately filled with "54545454" etc. until keyboard is disconnected.
daver2
10k Member
Based on the fact that you say the O1 with the keyboard cable (but no keyboard) works OK, I would say there isn't a fault with the main logic board...
The fact that both keyboards fail - but in different ways implies 1 of 2 potential causes.
1. The keyboards are really both faulty, but in different ways. I would use the multimeter set to 20 kOhms resistance full scale to check the key matrix connections looking for resistances < 10 kOhms (or so). You should see the 't' key with a low resistance in one case and the '4' and '5' keys with a low resistance in the other.
2. The pin that is missing on the keyboard connector is the electrical shielding, and (the lack of it) is causing cross-talk.
I suppose the next step is to see if your set-up does the same thing consistently from one day to the next. Again, if not, it indicates noise pickup or an intermittent problem.
Dave
The fact that both keyboards fail - but in different ways implies 1 of 2 potential causes.
1. The keyboards are really both faulty, but in different ways. I would use the multimeter set to 20 kOhms resistance full scale to check the key matrix connections looking for resistances < 10 kOhms (or so). You should see the 't' key with a low resistance in one case and the '4' and '5' keys with a low resistance in the other.
2. The pin that is missing on the keyboard connector is the electrical shielding, and (the lack of it) is causing cross-talk.
I suppose the next step is to see if your set-up does the same thing consistently from one day to the next. Again, if not, it indicates noise pickup or an intermittent problem.
Dave
VERAULT
Veteran Member
Dave, I have never opened my O1 keyboard to actually see how it works. Is it capacitive with foam? If so could it be degraded to the point that it is making permanent key presses on faulty keys? I guess the same could be said for the carbon pad variety if something conductive debris got in the way
NutmegCT
Experienced Member
Dave will give much more detail, but here's a link to the posts where I show pictures of the keyboard innards:
http://www.vcfed.org/forum/showthread.php?67552-Osborne-I-no-disk-drive-response/page4
and a link to a description of that type (membrane) of keyboard:
https://en.m.wikipedia.org/wiki/Keyboard_technology
Tom M.
NutmegCT
Experienced Member
Update. I found a working keyboard, plugged it in, and the Osborne works at last!
Felt good to see SuperCalc again, and to tell Eliza my troubles.
Tom M.
Felt good to see SuperCalc again, and to tell Eliza my troubles.
Tom M.
daver2
10k Member
Well done,
I was just thinking this morning on my walk that I hadn't heard back from you in a while.
So, it was most likely the original and replacement keyboard that you purchased that were both faulty.
Dave
I was just thinking this morning on my walk that I hadn't heard back from you in a while.
So, it was most likely the original and replacement keyboard that you purchased that were both faulty.
Dave
VERAULT
Veteran Member
Glad you have a working Osborne now. I wouldn't throw away those broken KB's just yet. They aren't exactly easy to come by and someone may be able to repair them.
I wanted to ask about the keyboard membrane. Did the keyboards membrane you were troubleshooting the membrane connection one on the left looked like it was rusted on top but on the bottom looked fine and the right membrane was fine? I just want to know because im fixing an Osborne OCC1 i bought and im fixing it to get it to even start up and i found the keyboard problem and want to know if i shlould just give up for now till i get a new keyboard.
NutmegCT
Experienced Member
Matthew - maybe I'm not following what you're asking. My keyboard had failed membrane *under* the keys. Your photo doesn't show the keys area at all - just the two cables that run from keyboard to cable connector.
Tom M.