The Dynaco ST-70 is a classic. I bought this amp from M3 Lover back in 2019. Tim had bought a new quad of JJ EL34 tubes, but hadn't done any other restoration or upgrades.
Since then, it's been re-capped. In addition, the RCA input board was replaced to allow space for proper cables. Finally, Eli Duttman's series SS diode tweak was done to provide extra PIV headroom and protect the tube rectifier.
Also, John Pons went through the entire amp checking resistor values replacing as needed and re-soldered some joints. After setting bias, John claimed a solid 35 watts per channel and the unit sounds great and is dead quiet.
The old 7199 tubes will be included along with a set of 6GH8A tubes with the 6GH8A to 7199 adapter. The amp currently is using Dynaco labeled RCA 7199s that I bought from eBay that test strong.
Lastly, John replaced the cage screws with stainless steel knurled knobs which are handy and quite nice.
The cage is in very good condition. As with most vintage electronics, the case shows some pitting and rust, but the electronics are good to go for many years and it sounds wonderful.
The only reasons that I'm selling the Dynaco is that 1) I have too many amps and 2) I got enamored with the McIntosh MC-30 monoblocks.
I also have the original Dynaco manual with all the instructions for assembly, schematics and wiring diagrams. Tim had also given me a lot of other info on modifications and other articles.
If you'd like more pics, let me know.