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Dynaco SCA-35 looking for advice

slayer44

slayer44

Well-Known Member
Hi all. I am new to the tube scene as I just picked up a Dynaco SCA-35 from a thrift store and need to ask the experts a couple of things. First, how do I power this up safely without blowing something up? can I use a DBT like solidstate equipment or do I need a variac? Second, when and if I get it turned on without a nuclear meltdown, will I need to replace certain components and where do I source them?...I plan to do some research on here first. I am sure there are rebuilds documented but I want to start with "Firing" it up.
Thanks in advance to everyone.
 
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@slayer44

I would first start with editing your thread title, as it's vague, with something like "Dynaco SCA-35 advice suggestions" you'll more then likely get a lot more respondents.

As to powering it up DBT or variac is the way to go

As to replacing components, if they are original that means they are about 50 year old and have more then likely lived out their shelf life. So yes some will need to be replaced

Sourcing components, there's a handful of suppliers still out there, Mouser & DigiKey are 2 that come to mind and seem to be referenced and suggested a lot here on AK.

Fwiw, Dynaco's are very popular her on AK and there are a ton of threads on them. I included a link below that might help you in your research

https://www.audiokarma.org/forums/index.php?search/70335927/&q=Dynaco+SCA-35&o=date
 
You're absolutely right Dswankey...Should have known better!...thanks for the great info. Will power up on dbt and see what I am dealing with.
 
^ Also once you get the thread title cleared up the tube guru's will come along, I see one has just popped in with a suggestion.

If you don't know how to edit just hit the "Report" button (lower left hand) in your original post and ask a Moderator to help you out.

Best of luck getting that Dynaco sorted out
 
Okay...couldnt resist looking under the hood!...I always check to see if anybody has made an attempt at fixing themselves...everything looks unmolested but not sure about the black wires from both transformers...is it an original coating, or burnt?
I have extensive experience with Pioneer and Marantz restorations/recaps, but these tubes are foreign to me.
 

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A DBT should work fine. I have rebuilt two SCA-35 using Dave Gillespie’s EFB boards. I replaced all the boards at once and enjoyed the work. I also have a stock SCA-35 that I bought while in middle school from Radio Shack. Amazingly it still sounds good when I periodically use it. The amp responds well to restoration.
 
Cool StuartB...I dont have a variac at the moment. Always trusted my DBT with rebuilds...plan on getting one soon though. At 17.5 watts a 40 watt bulb should work, correct...I understand these old tubes draw a bit of power, right?
 
LOL!...good for us...so, right off the bat, I dont have 4 matching EL84's. The oddball is a Raytheon 6BQ5 280 64-33...is this okay to have different manufacturers?
 
Most of us highly regard Dave Gillespie's EFB boards for these and the ST-35s. EFB requires matched tubes, unless you mod the mod and install a separate bias adjustment for each tube.
 
Attaboy @slayer44 now you're cooking with gas, I noticed in @daveshel recent thread he mentioned he just received some parts maybe he'll chime in as to where he ordered them from

Apropos of nothing related to this thread I used to ski Killington on the regular back in the day and dare I say Pico once or twice
 
Been a Vermont resident all my life but still dont ski!...those boards are reasonably priced. However, its hard for me to upgrade when I strive for originality in a purist sense...but I will think about it.
 
I haven't looked into what people think the sound and performance differences are between mods in Dave's Tronola article and units modified with his boards.
If there's not much, I'd opt to rebuild the unit to look stock with Dave's "invisible" improvements
 
I ordered from three sources. I started with Tube Depot for the tube sockets, most of the resistors, a few of the capacitors, and the diodes. I got these today. My order with Mouser has been shipped - more caps and hardware and a few resistors. Then there's a DigiKey order that's being held up by a back ordered heat sink. And already I see I'll have to make another order for one or two possible omissions, but I need tubes as well. I may get some from Tube Depot, some from Jim McShane.
 
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