[Peter Wieck]

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

[Peter Wieck]

On Wednesday, October 22, 2014 3:37:01 PM UTC-4, Peter Wieck wrote:
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.

Gradually making progress - and taking pictures along the way. The board is nearly done, I received the ceramic sockets yesterday, and now I am considering adapting a rusty old Dynaco chassis instead of purchasing new sheet-metal. I have some ideas as to how to get to that silk purse despite the cows' ears of stuff going into it.

Peter Wieck
Melrose Park, PA

[Frank Lucas]

I have made a ST35 clone (perfect copy) out of the trafos bought on ebay
long ago, no pcb but a solid 3mm copper plate put on a diy raw wooden
box. I love the sound of this and all the other 35 I have listened in my
life but I find Leaks Stereo20 slightly better with the right preamp.
Now I have a SCA35 that I could restore or take the irons out and build
another 35 clone. Eager to see what are your impressions on the board
you decided to use and to see pictures of the finished job.

Frank
Florence, Italy

[Peter Wieck]

On Tuesday, November 4, 2014 12:59:06 AM UTC-5, Frank Lucas wrote:
I have made a ST35 clone (perfect copy) out of the trafos bought on ebay
long ago, no pcb but a solid 3mm copper plate put on a diy raw wooden
box. I love the sound of this and all the other 35 I have listened in my
life but I find Leaks Stereo20 slightly better with the right preamp.
Now I have a SCA35 that I could restore or take the irons out and build
another 35 clone. Eager to see what are your impressions on the board
you decided to use and to see pictures of the finished job.

Frank
Florence, Italy

That will likely be this coming weekend. Linked is the drop-box of pictures to-date - I had not planned to share the progress photos before completion, but here it is. Note that wire-management is crude at this point, the final configuration will be be determined how stable the unit is when actually carrying signal. I *know* that running line AC next to signal wires is generally not the best of ideas, but I am using the ties to keep things out of the way. Nor have I 'shrunk' the tubing around the splices yet - that also will be done after testing and final layout.

I have five or six sketches on how I will finish it - in a house with two active cats, two very active dogs, and as often as not up to four small grandchildren, an open look is not going to happen. So it will be caged. As I am recycling Dynaco stuff, I have several options. Simplicity will be the goal in any case.

Now, as to restoring the SCA35 or cloning another - bluntly, I would restore it rather than clone it, the exception being if it is well-and-truly not salvageable. There is a nifty power-supply board available that pretty much takes care of that issue in a simple and elegant way - including adding time-delay, and restoring the boards is very, very easy.

Peter Wieck
Melrose Park, PA

https://www.dropbox.com/sh/464rqwpo6...tIv8RDRia?dl=0

[Peter Wieck]

It is making music! For testing purposes, I am feeding it from a Citation 14 tuner (as it has a gain control for each channel) and into a very small pair of AR speakers - the satellites from their Athena system. Quite nice for what they are. I have a few more pictures which I will load into the drop-box tomorrow - and then onto wire management, aesthetics, and adding the phono pre-amp and volume control.

So far, so good. I am quite pleased with the sound - no hum, no hiss, no crackles of any nature when quiescent. And no hum/hiss/crackle when fed from a source as well.

Peter Wieck
Melrose Park, PA

[Peter Wieck]

Latest pictures added to the drop-box.

https://www.dropbox.com/sh/464rqwpo6...tIv8RDRia?dl=0

Note that they are alphabetical, not by date.

Much to do yet on aesthetics, adding the phono section (extra RCA jacks on the rear), and wire management. I give it another week of everything-but-aesthetics.

Peter Wieck
Melrose Park, PA

[Peter Wieck]

Update: The amp has now been running for about 2 weeks without a blip, all transformers cool. So, Now I will add the phono preamp board and run that for a while.

Once that is proven, I will finalize wire management, then move on to aesthetics. This last will be 'interesting' as every part and piece of the amp except for the main board and the components on it is recycled, up to and including much of the internal wiring, screws, nuts, bolts, controls, jacks and more. So things are much larger than they need to be...

More pictures shortly.

Peter Wieck
Melrose Park, PA