Sad news and a great loss. Terry helped me with my first Mac rebuilds with plenty of advice and guidance. Always relied on him to help with troubleshooting.
Very nice and clean! Would be curious about the rectifier and power tubes in them. The rectifier looks like a 5U4G, and not a 5U4GB so the voltage drop and max voltages are different. 5U4GB is spec'd in there.
Tube# - Fvolt - Famp - Vdrop - MaxPmA - MaxPv
5U4-G - 5.0 - 3.0 - 44...
Might sound silly, but try a different 6AN8. I had a similar problem with a Heathkit UA-1. After poking and redressing leads, I swapped the tubes out, one by one, until I determined it was a bad 6AN8. No more oscillation.
The rights to the company names don't expire like patents or copyrights. Someone likely held the IP rights to what was left of those "companies" and M Mathews purchased/licensed those rights.
Toni Fishman did the same with Telefunken's microphone production. He also bought the rights to...
Well, they probably could, but the demand would be so small that the price would be extremely high. The new 670 compressor is $35K. They will likely sell maybe 2 thousand of those over the run of production.
Some interesting news coming out of NAMM. Anyone with an interest in studio recording knows this piece of gear and its status/history.
The 660 & 670 are really Fairchild's lasting claim to fame.
https://www.mixonline.com/the-wire/fairchild-debuts-660-compressor-limiter-at-namm-2024
They are indeed foil and not plates. I have a very clear unit that I can photograph with a grid/size chart as well as color chips to get it right. It's the mirror gold tone that can be difficult to match.
My .02¢
Cosmetics:
They are pretty rough IMO. Give everything a good cleaning and see how you feel about them. You could repaint the trannies using an autoshop that can match and do a proper spray on them. The chassis' don't bother me so much and it would be cool to have the prototype...
Green underside was from the early units. The circuit was also an early version as Dave G points out in his great restoration thread.
https://audiokarma.org/forums/index.php?threads/rare-beauty-fairchilds-275-amplifier.909896/
They are Norelco R2R decks. The Tandbergs came later.
https://louisarmstrongfellowsblog.wordpress.com/2021/05/21/armstrong-as-a-consumer-of-twentieth-century-audio-technology/
https://www.nytimes.com/2020/02/20/t-magazine/louis-armstrong-home-queens.html
Was the box damaged, bashed or dented? If it was, it was the shipper. If not, the amp likely was that way when shipped. If #1, file a claim with the shipper, if #2, file a claim with paypal.
Either way, a sad state of affairs.