Mod 122C too...it is also an exceptionally stable instrument. I have a 577D1 as well, and it takes a couple hours before it is fully stable. I also have a second Type 575 with Mod 122C, equally as clean, but it's not so good functionally. I will be getting to it in the repair queue, possibly this winter when it's more fun to have toob gear heating the lab.
Wow...two pristine 400V 575 ... and me just a crusty 200V one. Oh well... still so happy to have at least one example of the beast, regardless of specs or condition !
577 only one I saw for sale here was a year ago and teh guy wanted 2500 Euros for it... not even powered up / 100% unknown condition, yeah right !!!
I also gather these are a nightmare to work on, have plastic bits that break, and known weak points on unobtainium parts.. can't remember the specifics but quite scary especially given the price of the thing !
My 575 was only 150 Euros, 15 times cheaper than a 577 and it's all bullet proof stuff, or fairly easy to repair at least. It's a boat anchor after all, it does come with its advantages...