88-4mcs

[sje]

Concerning the extender card: I'd guess either mechanical wobble (especially without card guides) or finger connector tarnish. The latter was a recurring problem with the IMSAI cards. An occasional treatment of the contacts with a pencil eraser did the trick.

I am very encouraged that other boards are showing good progress. I don't mind keying in a small bootstrap, but toggling a 16 KB chess program is out of the question. So an SIO board is a minimum requirement (after memory). Alas, none of my recent machines has a serial port, but I've got a USB/serial converter from Keyspan that should work.

About the pots: if neither Digikey nor Mouser carry these, then I wouldn't know where to look. I recall that there were some smallish "dial a resistor" discrete pots that were available back then and might also be around today.

The 8800b full function front panel (not the turnkey version) is a big improvement over the original with better toggles, better graphics, a slow auto stepper, and an accumulator display. I do not recall if the updated front panel board is wire and signal compatible with all the original hardware.