I'm a newbie here.
I just picked up a Darth Vader Apple II plus. Got it to boot with chime but only the reset and CTL keys work. I know tose keys don't go through the encoder. I'm trying to figure out if the problem is on the encoder board or down stream (main logic board).
I have +5v and ground going to the encoder board.
All caps have been tested, encoder chip reseated, ribbon cable between main board and encoder checked. All good.
Put a scope on the encoder board and checked the 555 timer (no pulses) and the encoder IC (no pulses either).
Are there other tests I could do to confirm the encoder IC is bad? I also tried pulling the encoder to see if it was loading down the 555 or other logic chips. Nope. I can replace the logic chips and 555 but I don't think they're the issue. Just trying to confirm it's not on the main board.
If the card is bad I think I'd rather go with Encoder Plus card on Ebag. It's a replacement daughter card that aslo adds other options.