Hi everyone,
Now that I have my apple 1 working, I found a Franklin Ace 1000 keyboard. I replaced all the foam pads in it, and cleaned the board. But when I hook it to the apple 1, the apple 1 doesn't boot anymore (we can guess the characters grid on the screen, but that's it, no chars). My cable work. I tested with 2 different cables (12cm and 50cm long) that both work with a "USB keyboard to Apple ][" adapter. The lock LED lights up tho.
I'm going to test the power consumption when I can. My first guess is it's pumping too much current. I already test for shorts in the cable socket and found nothing, beside some NC pins connected to +5v or ground, but since my cables don't do anything with those NC pins, it's not a problem.
Could be a dead chip or resistor/capacitor, but before unsoldering a bunch of things to test them, wanted to have an opinion on the issue. Maybe I'm missing something obvious.
Thanks
-Ben
... you can check -5V, +5V and +12V at the corner pins of the DRAMs, and -12V at pin #1 of the character generator ROM at D2/D3.
First measurement with no keyboard cable attached, note down the numbers, then attach keyboard cable, measure, note down numbers.
This should give a clue if it's a power supply problem and if a regulator died (very rare as the originals self-protect but there are knockoffs where the protection circuits have been removed or tampered with, since these copycats never figured out how the current limit trip point is set in these devices, it's a foul trick that happens in the wafer fab).
The other possibility is CLR SCREEN (keyboard connector pin #12) being actively driven "L" by the keyboard when the key is not pressed, which will block the cursor logic and the consequence is that no characters can be written to the screen. A small signal diode in this signal line with cathode to the A1 and anode to the keyboard can remedy that lockup. Woz saved 3 cents for that diode ;-) and countless A-1 builders have wasted many, many man-hours to hunt down that bug. Note that the A-1 manual calls for a simple, plain switch to +5V there. No problem is this rule is followed.
- Uncle Bernie
Thanks, that was the clear screen signal.
I removed the wire on my home made "apple2 to apple1" adapter, and it works perfectly. I already had soldered a clear screen and a reset buttons on it anyway (to be mounted on a case later).
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