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So I recently finished my Mimeo-1 (so excited!), and other than some bad 7400s, everything has gone smoothly. I'm now at the stage to connect a keyboard, and have an Apple-II Plus keyboard that I thought would do the job. However, the only keys that output what they should are Reset and Space, and a few of the number and punctuation keys. Nothing will display letters.
1234567890:- maps to 10145458908-
QWERTYUIOP maps to 15%0495)-0
I checked the daughter board and saw that the encoder is an NKBD-931 8003UX which I'm guessing is the problem as I've only seen people use KR3600 or MM5740.
I don't know much about these though so I'm not sure if the keyboard is at fault or if its something on the Apple-1 side.
If the problem is the NKBD-931 8003UX, could I just swap that with a KR3600 chip?
Thanks for any help guys!
(I attached some pictures of the encoder board, and my finished Mimeo-1 for posterity)
Assuming the wiring is correct...
Most likely cause... You have one or more shorted keys in the matrix on the keyboard. You need to search online for a copy of Winston Gaylor's Apple II book for a matrix schematic of the keyboard. Then you can use an ohm meter or continuity meter to see what's up.
Corey mentioned "if the wiring is correct".....
what is meant by this term:
The socket of the keyboard at the Apple1 and its replicas
IS NOT THE SAME PINOUT
as at the Apple II and therefor
YOU SHALL NOT PLUG IN A APPLEII KEYBOARD
into an Apple1 Keyboard socket
WITHOUT CHANGE OF WIRING !
See this graphic:
IF YOU PLUG IN Apple II-keyboard without change of wires
you take risk of damage
either at the chips of the keyboard or at the Apple1 replica !
Hey guys, thanks for the input. Unfortunately I did use the vintagemicros adapter board off of eBay that I hear Mike Willegal had a hand in designing, so the wiring is likely okay.
I will likely have to try checking it for shorts in that case. However, it supposedly worked just fine in an Apple II just recently so I don't know what might have happened to it. Slightly frustrating too is that some keys do work as expected.
But I guess it's better that the keyboard is malfunctioning rather than the Mimeo.
Thanks for the help guys!
There are different adapterboards out there....
please post picture so we can see what we are talking about...
If it is the PS2 adapterboard - that worked fine in an Apple II
then it has been wired for the Apple2 and not for the Apple1 !
( see differences above )
and if it is another adapter then the problem might be the adapter....
are you using true Apple II keyboard or are you using PS2 keyboard with adapter ?
different answer from you will lead to different answer from us !
Who told you the keyboard? Worked and did you see it working yourself. I have bought many keyboards on eBay that were supposed to work and they don't. I will typically have to go to town on them with ISP and elbow grease. Then they seem to work fine.
I can't seem to figure out how to attach an image in a reply post, so I added a picture of the adapter board in my original post
Heres the link to the same adapter on eBay with more info
I did see a post recently in which Mike Willegal mentions he designed it and linked to the vintagemicros listing, so seems like it should be compatible, but it might be the weak link here.
It is a true Apple II Plus keyboard, not a PS2
I didn't see the keyboard work; it was an eBay find. (I do feel it could be wrong to use an Apple II keyboard for something other than an Apple II given rarity, but it's really the easiest option right now).
Anyway, the person who sold it to me apparently saw this post and sent me a message confirming again that it did work before shipping.
I don't know if this is relevant or not, but I have noticed one thing which seems strange. On startup, instead on seeing _ and @ I see = and @, and instead of seeing / on reset I see >. I assumed this was just a difference in the char rom or something though, but could it be that it's just not showing the right characters for everything? I doubt it but figured I'd mention that.
I don't currently have an Apple II on which to test it without the adapter. Though I think one of the Briel replicas are supposed to work with plugging an Apple II keyboard directly, maybe I can try that to see what happens (once I replace it's 74LS00 that's temporarily residing in my Mimeo lol)
thanks for the update with the links.
The reason was to view the adapter and determine which kind it is.
There are several adapters out there: some are what we call "active"
with a Chip that performs a kind of "translation" ( by transforming
the signal from a PS2 keyboard to a A1-Keyboard signal )
and this one is what we call "passiv" - because it just replaces by
its traces the adapting wires without any chips....
in bad luck cases a "active" adapter might fail by mistakes of the chip....
but in this case we are sure that this can't happen due to the kind of
the adapter - as it is "passiv" .... the only possible mistake could result
by plugging cables to the adapter in wrong oorientation or by misalignment
of the plug on the pins....
At the adapter there are white dots printed to indicate at which side
of the pins there is pin 1 ( close to the pushbutton ) and
at that side the cable should be plugged in that way
that the red marking of the cable is at that side too....
If then the cables are also plugged in correct at the devices ( paying
attention to the markings of pin 1 at the keyboard output connector and
at the A1 keyboard input socket ) then everything is perfect and then
the mistake can only be charged to the keyboard itself - if the chips of the
Mimeo board have been proof to operate correct.
In that case i'd prefer to pass over the torch of this thread to Corey completely
because he has far more experiences with keyboard trouble and debugging them...
Just to get also sure about the MIMEO it also might be usefull to add also a link
to the startup picture of the monitor screen after bootup has finished and the
">" is displayed.
First things first. You need to unplug the keyboard and wires up a reset and clear screen set of switches only to a cable/dip connector. You don't want a keyboard plugged in when you do it. This will eliminate the question of the keyboard not allowing a clean clear and reset. I don't like the idea of using a wires shoved in the socket to reset and clear without an actual switch.
Once you do that you should be able to get a clean prompt after a clear and reset. Then we can work on the keyboard issue.
I've never used the adapter from vintagemicros, but if it's based on Wendell's diagram, there is also a trace on the keyboard controller that needs to be cut. I don't have the info in front of me.
As for keyboard working before and now after. As I mentioned, shipping the keyboard could cause a new short. I have had that before a the bumping around caused a switch or two to have an issue and mess up the matrix. Tracking it down isn't that hard using a continuity tester. Then is cleaned the switch or worst case replaced the switch. You can find replacements or I can help with that.
It looks like bit 1 is stuck as zero. Most likely you have a bad 7404 on the keyboard encoder, which is part of the keyboard. This often happens when they are plugged in backwards.
If I'm understanding his posts, I think he also said he doesn't get the correct prompt when reset. So maybe he has two things going on. The prompt wouldn't be affected by the bit being stuck. I didn't get as far as a binary ascii chart yet. But good catch. I find with old keyboards it's usually something mechanical before its digital and I'm also nuts about not plugging the keyboard in backwards, but you have had more experience with people using Apple II keyboards on the A-1 to know common mistakes.
Note to everyone, you should put a white dot on your cable connectors to mark pin-1. This way it's really obvious if you plug it in wrong. I find the little notch may not be obvious enough for many people.
Okay thanks for the input - I tried some stuff and some things are behaving strangely.
Firstly, I attached some pictures to my original post showing cable orientation. It looks fine; the blue wire is always lined up to the pin 1 markings on the PCBs.
I also attached pictures of the startup screen and the reset prompt as per speedyG's suggestion.
I tried a reset without a keyboard and got the same < prompt.
I'm beginning to think there might be something awry on the Apple-1 side of things.
i'd just mention 1 point:
at the picture of the screen with the expected prompt:
the white dot pixels in a kind of sqare pattern......
that looks a bit like a stuck bit too....
wait for the opinions of mike and corey ...
they might have seen such a symptom...
Was that startup screen from a clean power on? In other words did you wait a few minutes between power cycles?
If yes, I think you have a bad 2504v. Could be something else, but swap the chips around and see if the pattern changes.
change of pattern means that the white dot moves in it's position
The startup screen was a clean power on.
I swapped some 2504v chips around, and instead of = and @ I'm getting Y and @, so looks like you were right!
Instead of a / or < on reset I'm getting a X. Everything I type no matter what key shows up as Y.
Sorry for not thinking of the 2504s earlier. Sourcing those is going to be a challenge though.
I did plug the keyboard directly into a Replica-1 TE without an adapter after reading in the manual that it is supposed to work that way.
No matter what I type, I was presented with solid white arrows and question marks.
This is likely something entirely different though, I should get new 2504s and see what happens first.
so that splits the problem in 2 different problems :
one problem with the keyboard
and one with the mainboard....
so you can work at the first problem at the replica
while you wait sourcing the 2504s
Well theres a nice set of tested, date correct 2504s on eBay, maybe I'll just splurge on those.
Thanks for the help so far speedyG, Corey, and Mike. I'd be totally lost without this forum!
alternate source for 2504s:
Thanks, my bad ones came form Unicorn the first time so I'm a little hesitant to try it again, but they are cheaper.
I guess they can't all be bad...
Let unicorn know, they are good with customer support. I don't think he has a way of testing these specific chips so it might take a try or two.
I thought about building a tester at one point, but they are easy enough to check in a Mimeo. I've been told 2504V are very static sensitive, but to he honest, so far in all my work on original Apple-1 systems the only one I know of with a bad 2504 was Wendell Sander's and that was back in the 1970's, so it must be a few "Bad Apples", pun intended, in the latest NOS lot floating around there.
I'd rather more guess that a larger bunch of "faked" chips from a
chinese junkyard distributor got "relabeled" and entered the market....
and it seems quite a bunch still floating around from that source...
That could be true, but I would then expect all the chips from a single vendor like Unicorn would be bad. It seems to be a handful that sometimes appear in the kits.
not if they had still chips in stock while they ordered new bunch of chips...
then two different charges have been mixed up...
It looks like, based on other posts and my kit, that a lot of the Unicorn 7400s tend to be bad as well. They're a little easier to diagnose and find replacements for though.
I think I saw one post where someone made a flow chart for diagnosing specifically which of the 2504V were bad, I'll have to go dig that up. Does anyone have any process to find the bad ones?
you remember correct !
Member Cyril56200 posted a thread with an excellent organigramm for diagnostic purposes at:
and at the first posting is a link to this chart:
I guess that's what you mentioned ?
I've never had a bad 7400 series from Unicorn. Mike Willegal may be able to comment on that, he used them for a while when he was supplying parts kits himself.
Yup thats exactly the chart I was thinking of! Thanks!
I think I saw Sherlock had problems with 7400s a while back, though I could be mistaken there.
Hey guys, made some progress. I managed to obtain some working 2504Vs and I'm now getting the proper "_@" on startup and "/" at reset!
Rather than typing random characters, the Apple-II Plus keyboard now only resets and types _ on the Mimeo and types either "?" or solid white arrows on a Replica-1 TE.
Just to clarify, is this most likely the result of shorts on the matrix or a bad 7404 on the keyboard? I guess I should probably start checking...
So I replaced the 74LS004 on the keyboard encoder board and now the keyboard works as expected!
Thanks again for all the help that got me this far!