• Please review our updated Terms and Rules here
  • Exhibitor application for VCF West 2022 is now open! If you are interested in exhibiting, please fill out the form here.

Altair 8800 Bring-up Questions


Experienced Member
Dec 19, 2013
Hawthorne, CA
Recently I purchased an Altair 8800 from a friend, S/N 221999 (looks like someone sliced off the 'A' or 'K' from the end of the serial number, but I suspect it's a kit build).

I ended up with the following:
-Display/control board
-Power supply (likely a Rev 0)
-Backplane - 1 ~.062" thick 4-slot backplane card, 2x ~.125" thick 4-slot backplane cards
--1 broken card guide, the rest are all intact
-An 88-2SIO Rev 0 card
-Cromemco ZPU card. (The front panel cable has be re-soldered to an IMSAI-style DIP connector to match with the ZPU)
-Unidentified ~16K DRAM board
-The chassis has cabling for what looks like the 88-ACR and 88-4PIO boards, but they didn't make it all the way to me.

I'll post some pictures when I get a chance.

I just built up one of Josh B's JAIR 8080 cards and tested it in my running system, so I would have a known-good starting point to test other things.

What I'd like to do:
1) Verify power supply is safe to use
2) Test front panel + JAIR board
3) Add 88-2SIO
4) Get Altair 4K/8K BASIC running via the 88-2SIO - using a modern PC to feed in the data instead of a paper tape/cassette

What's the best way to checkout an Altair power supply, beyond taking disconnecting everything and firing it up and measuring voltages with a multimeter?

Another thought I've had is to just take out the power supply and replace with some modern switchers, setting it aside in case I ever want to sell the machine in accurate condition. But I think it's at least worth trying the original supply.