PDA

View Full Version : Mystery "MITS" CPU Boards



glitch
October 5th, 2017, 12:12 PM
I recently picked up a lot of vintage boards that included what appeared to be MITS Altair 8800 rev 0 CPU boards:

(album with closeup images here: https://imgur.com/a/m6djg )

https://i.imgur.com/UOfLQaY.jpg

It's clearly the same pattern as the MITS CPU board, but it's not labeled as MITS, and it has no silkscreen. The boards came with some regular MITS boards, other S-100 stuff, and some non-S-100 boards. I at first thought they were someone's homebrew clones, but they have plated-through holes, which is unusual for homebrew clones. Any ideas on what they are?

I've got four, they're in various states of not-assembled, ranging from the pictured bare board to some sockets/connectors stuffed and soldered.

Marty
October 13th, 2017, 09:30 AM
Hi All;

Glitch, I would be Interested in One of them, if any are for sale..

As my 8080 CPU Card got some traces torn off and so I could use a replacement, I have ugly wires in their place..

THANK YOU Marty

Chuck(G)
October 13th, 2017, 09:59 AM
Glitch, are you certain that the holes are plated through?

I suspect that they're just someone's clones. Do they match trace-for-trace with the real MITS CPU boards?

glitch
October 13th, 2017, 10:42 AM
Absolutely certain -- they're not inserts or conductive ink or anything, they're real plated through holes that have then been tinned. It looks like an electroless tin process.

They do match to MITS boards, aside from the MITS info not being there.

Chuck(G)
October 13th, 2017, 11:16 AM
If the traces are the same, then they're not prototypes. So probably just copies. Was the PCB artwork ever published? I know that PE did quite a bit of that kind of stuff.

glitch
October 13th, 2017, 12:18 PM
I've talked about this with Herb Johnson, he says that PE did in fact publish the artwork. I'm betting that's what it is -- a mostly well done hobbyist-made board from PE (or similar) artwork. There were other homebrew boards in the lot that this one came from, none of them were through-plated but most were prototype boards where it likely wasn't required. Oddly enough, someone soldered bond wires across all of the terminals on the protoboards and electroplated gold on them, and then removed the bond wires. It looks like they didn't plate nickel down first, and the copper has migrated through the gold.

Chuck(G)
October 13th, 2017, 12:48 PM
Well, page34 sidebark (http://www.americanradiohistory.com/Archive-Poptronics/70s/1975/Poptronics-1975-01.pdf) does, in fact offer a complete set of PCB artwork with drilling guides for 0.40 to cover postage.

What's interesting about the original PE 8800 article is that the boards are shown as a stack,held together with spacers and through-bolts and not what originally rolled out as kits.