This classic amplifier was rebuilt by audiogon member cjkinpa. I have very few hours on the amp. The amp is in very good cosmetic condition, except for a small chip on the back of the top plate where the tube cage hit the chassis. There is a very faint mechanical hum from the transformer that is inaudible from the speakers.
I have not had any problem with the amp. It works and sounds wonderful. I am selling for financial reasons.
From cjkinpa's description:
"Here is a beautifully restored Dynaco ST-70 power amplifier. The ST-70 is the most popular power amp of all time - over 300,000 of them were sold. When properly restored, they are still among the best out there today and will outperform many amps costing 4 times as much. This amp was stripped of all components and only the PA-060 power and A-470 output tranny's were kept. Chassis and tranny's were sanded primed and painted. All new filter electrolytics were installed, doubling the capacitance; new bias supply with I.C. caps, precision resistors and new bias pots; old phenolic driver board replaced with new Triode Electronics driver board. Also added were new cooler running ceramic tube sockets, new gold plated RCA jacks and new binding posts. As noted this amp of course, has the original cloth lead transformers which are among the best ever made. The newer replacement output tranny's found in the kits available today are not even in the same league as the original Dyna A470's.
The amp sounds absolutely wonderful - rich, tight bass; smooth high end, and a lush midrange. The buyer will be extremely happy with it. Tubes are a quad of E.H. EL-34's, russian mesh plate EF-86 and RCA black plate 12au7 driver tubes, and a new 5ar4 rectifier."

More pictures at:
ST-70 pictures