here's the manual for the MR-70:
http://recordist.com/ampex/schematics/mr70man/mr-70man_lr.pdf
And I think I know where to get the sales brochure too...let's see...AH! Here it is:
http://recordist.com/ampex/docs/apxbrochures/mr70/mr-70.pdf
So...what's your experience with tape decks?
I think the MR-70 is one of the most alluring tape decks ever, and some say there has never been a better sounding machine. On the other hand there are others, very respected and who have a basis for their opinions, who say that a properly tuned 440 can give the MR-70 a run for its money, at least make the gap very narrow.
The MR-70 is very rare. That can be desirable, but it comes at a price...and its a pretty high price and you need to be surrounded by people that can help you if you are going to get into an Ampex and you want it to run right. That is what I was told when I started down the Ampex path and I heeded it but only so far as was convenient for me. That's all different for awhile now...its a must.
So, I consider my MM-1000 an advanced level project for the average DIY-er. I've needed a lot of help, but its doable for me. The idea of the MR-70 feels advanced for me. I'm not ready for it.
Oh, and there were some issues with heat and microphonics on the nuvistors IIRC.
Can you just run it and not worry about it running tip-top? Sure, but why waste an MR-70? You could spend a lot less money for a deck you want to just run and not properly maintain it...I realize you didn't say you wouldn't maintain it...my point is that if you go for an MR-70, be prepared if you want it to run proper.