I was grubbing through my various parts-boxes the other day and found out that from various repairs and salvages, I had accumulated a complete set of Dynaco 35-series iron - two OPTs from a ST-35 (identical to the SCA-35) and an SCA-35 power-transformer. And, a couple of spare generic Dynaco vented chassis, assorted controls, boards and more.
Hunting for ST-35 clones (I do have both a factory ST and SCA), I found Shannon Parks Audio, with an intriguingly inexpensive ST-35 clone board - 90% of the work done and a pretty good circuit, at least from my reading.
http://parksaudiollc.com/st35.html
Looking at the parts list cross-referenced to Mouser and what I have in hand already, and my total out-of-pocket will be less than US$90, inclusive of the board. I will also add a phono-pre-amp to the project with a selector-switch that both bridges in the pre-amp, and brings power to it. No need to heat up two additional tubes unnecessarily for those few times it will see vinyl. Add a volume control from the same junk-box source and I might wind up with a half-way decent little amp useful in various ways. It will certainly divert some dust-catchers back into the functional world.
I will gather pictures, and post progress as it is relevant.
if this works out, I think I might tear down my previous little project using Fisher 500 iron, and rebuild it adapting the Parks Audio ST-70 clone board. The (very simple) circuit I used does not satisfy me for stability, although it sounds moderately OK. That was never quite formalized onto a purpose-built chassis with appropriate finishes - it was (and remains) pretty much a breadboard set up on a copper-foil laminated plywood base - a bit of left-over construction material that happens to take solder very nicely. I was (and remain) never happy enough with it to install it permanently.
Peter Wieck
Melrose Park, PA