Hi Phil,
“I was there when…” in high school we saw the ad for the MITS Altair 8800 in Popular Electronics and all wanted one. Well, I built mine in 1976 as a senior high school electronics project and it is still running today. I went on to sell them and have been (and still am) involved with computers.
The boards you have are the 88-S4K, or 4K Synchronous Dynamic RAM cards. These cards were created by MITS and actually sold for near cost (without the memory chips) to owners of the ill fated 88-MCD or Memory Card Dynamic RAM. These original cards were so badly designed that you could measure 200mv of noise from one side of the card’s “ground” plane to the other. MITS offered these later boards as an “apology” to all of us who had purchased the original cards. They (MITS) gave dynamic RAM quite a bad name and it was shunned in the later Altair/S-100 bus world. The newer 88-S4K cards are a much better design and were fairly temperature stable. However if you have the opportunity to replace them I would recommend it.
About the voltage regulator on the +8V – this was part of a power supply upgrade and is part of the difference between an “Altair 8800” and an “Altair 8800A” – nearly all of the “A”’s have this modification.
You may find this site of interest:
http://frankbarberis.tech.officelive.com/default.aspx
Frank