Hello,
I am quite new to playing around with the Apple 1 and have had a clone lying around for a few years now. This week, I finally got around to playing with my clone, and it all worked fine until I had to reconnect the keyboard. Now, it doesn’t work quite as expected. It seems like I might have blown or shorted something on the Apple 1 itself or on the keyboard.
The Apple 1 startup fine, and I can reset it from the keyboard. However, the characters are swapped as follows:
A = I, B = J, C = K, D = H, E = I, F = J, G = K, H = H, I = I, J = J, K = K, L = M, M = I, N = J, O = K, P = X, Q = Y, R = Z, S = [, T = X, U = Y, V = Z, W = ], X = X, Z = Z.
I hope someone can direct me in the right direction.
Kind regards,Claus
If you have a chance to test the encoder in your keyboard? I've often heard that they are very susceptible to static, unfortunately it kills them. Something similar happened to my Apple //c a few years ago, also the wrong characters started appearing on the screen. I replaced the encoder and the problem was solved.
I tried to replacing the MM5740AAE chip with another one I had as spare, but still the same problem.
Hi Claus,
according to the symptoms you wrote, I believe you might have line B4 always stuck to 1 and B3 line always stuck to zero:
claus.png
Perhaps a tin blob, and/or some missing connection?
Good luck and let us know,
ciao,
Claudio Parmigiani - P-LAB
PS Edited: the scheme above applies also to S --> [, but strangely not to W --> ]: it should have been W --> [.
It might be a typo, or something that need to be investigated more... ;-)
The Apple I uses an ASCII encoded keyboard, so you can translate each of your key codes to binary and see what is odd about them, then refer to the schematics in the manual.
From this it appears that the bit 3 may be stuck on, and bit 2 stuck off (or there are other problems). Check for any cracks around pins 2 and 3 of the socket at position B4.
If there is no physical damage to the sockets or traces, then the 6820 PIA appears to be damaged.
The keyboard is connected directly to this chip, so it is liable to be damaged by any static discharge picked up over the keyboard cable.
Sounds like a task for my ASCII Keyboard Tester, see https://www.applefritter.com/content/ascii-keyboard-tester-pcb-and-kits. Also take a look at the manual, this could be interesting to the topic starter as well.
If you have a spare PIA you could swap and try again.
Thanks for the good advise. The short on pin 2 and 3 directed me towards a faulty IC. One of the two Hex inverters (7404) on the keyboard is failing the test in myTL866 chip tester, so I order some new ones. I will replace and get back if this will resolve the issue. Thanks again, much appreciated.
Great! A quick fix.