Some Altair questions, if I may..

First off, an update - All of the 74XX chips on the CPU board seem to test out just fine. I'm having a little trouble figuring out how to set up a really +comprehensive+ test for the 74123s and the 7473 / 7474 chips, as I'm not yet up to speed on stuff like "retriggerable monostables with clear" and "dual J-K flip-flops". I did come up with some basic sanity tests though, and that is what helped me cull out the bad 123s. At least I have plenty of spares of those types, so can always check by making subs. On Thu, Aug 28, 2014 at 7:26 PM, Chuck Guzis <cclist at sydex.com> wrote: Bear with me, it's a bit of a complicated answer. Yes, the front panel AC switch is still on the board, but it's not presently connected, nor do I know much about the 'early' history of the machine. By early history, I mean the period of time between the original build / first light and the eventual +removal+ of the D/C panel. When I received this machine, it was configured for a Z-80 system, but in a VERY non-working state.. what a cobbled mess!! Both the D/C panel and 8080 CPU board were in bags. The panel wiring harness had been _de-soldered_ from _some_ mainboard, but not from the _present_ mainboard - the present mainboard had the panel wiring _cut_ away to the machine, so it may be that the mainboard was cut-out from a second Altair machine and transplanted into mine. As received, the mainboard had 1/4" cut stubs of white wire protruding from all of the hookup holes. The D/C board had also experienced a small, localized fire at some point, around the extreme lower-left corner (as viewed from the front). As mentioned, I cleaned up and tested / replaced as needed any parts in that area. I'm assuming that whatever may have caused the fire could also be responsible for the rest of the bad chips on the D/C panel. Doesn't really matter, though - as it needs fixed in any case.