Dynaco amplifier SCA-35 output transformer details

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » Dynaco amplifier SCA-35 output transformer details
Meyer Rochwerger
Meyer Rochwerger
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08.Jan.20 22:09

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Dear friends,

I bought a Dynaco SCA-35 amplifier missing both output transformers (type Z535).

So I need to build a new pair of transformers from scratch due to the high values of transformers that are for sale on the web plus the high postal rates for Brazil.

Searching the web, I found some characteristics of the windings: 

The primary has 8000 ohms CT to plate 

But the information about screen winding (CT to screen) is missing.

If anyone has this information to provide me so that I can proceed to the work.

I'd be very grateful..



This article was edited 08.Jan.20 22:19 by Meyer Rochwerger .

Achim Dassow
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09.Jan.20 15:33
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Dear Meyer,

under w w you could find more about the UL taps:

...comparison of our Z565-48 to the original Dynaco Z565... high frequencies the noise/THD of the amplifier is greater than that of the transformer:
the actual bench tested distortion figures at full power (17.5 watts) for the transformer itself are as follows: 1KHz 0.019%, 10 KHz 0.032% 15 KHz 0.029% 30 KHz 0.048% 40 KHz 0.058 %.
This is practically within the measuring margin of error the same as of the original Dynaco unit.

The UL taps are at 25%, per Dynaco spec for this output.

Here's a similar comparison of the original Dynaco, Magnequest, Handwound, and two models of Hammond transformers ...
Note in particular the comparison between the Dynaco part and the Hammond 1650F, comparably priced to our unit.
Transformer specs are: 8000 ohms CT primary with screen taps, 4 & 8 ohm secondary.
20 Hz to 20 KHz response at 17.5W, within 1 db (30-15 KHz @ 35W)
Max DC per side (suggested) 80 ma.
Height 3 inches (75 mm) width 2 1/2 inches (63 mm), depth over covers 3 1/8 inches (80 mm), mounting centers are 2 inches (52 mm) by 2 1/4 inches (55 mm).

I hope this could help you to successfully build the transformers.


Meyer Rochwerger
Meyer Rochwerger
BR  Articles: 112
Schem.: 320
Pict.: 1803
09.Jan.20 19:36

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Dear Achim,

A colleague from the "dynacotubeaudio" forum provided me with the information I needed.

"Typically the ultra-linear screen taps are at 35-40% of the output transformer primary" (he said...)

Now I can proceed with my project ...

Anyway thank you for your interest in helping me.