3603 wiring.

Diamondj421 · Feb 8, 2017

I am building a solid state EQP1A3 and using Sowter 3603's as input and output transformers. I can't for the life of me figure out how to wire them though. I'm given 6 colored wires that I see no where else to compare to. Can someone help crack the code?

Thanks!

Pusch3l · Feb 11, 2017

Datasheet says its a 1:1 iron.
Pin 1 (+) and 3 (-) seems to be the primary and Pin 4 (+) and 6 (-) the secondary.
Are you using them on Aarons Gainstage? I saw edcor and lundahl mentioned in the instructions (2+2:1+1). Maybe there is the error in your low gain. Do you have another iron for testing purposes?

Diamondj421 · Feb 11, 2017

Brian from Sowter got back to me and said what you are saying. With the black lead attached to the grey lead. Upon connecting them in this fashion I had no signal. Took them out of the circuit and the EQ worked fine minus the 20dB gain loss. I went with this particular transformer because Sowter said it's they're replacement of the HS-56V. I really just want it to sound as close to an original SS Pultec as possible. I'm unsure as to how closely I should follow the original schematic though vs the PCB I'm using.

Pusch3l · Feb 11, 2017

I think your wiring was ok. You can try without the grey and black wire connected together.
Did you hook up both irons? What happens if you just put the output iron between the gainstage and the output xlr?

Diamondj421 · Feb 11, 2017

I did have both hooked up. I read on VintageWindings.com that you have to connect the output transformer the opposite of the input. There's no step up/down though right? I'm heading home from the hardware store now so I'll try connecting the output when I get home. Next I need to figure out why my damn bypass isn't passing signal. The fun never ends!

Pusch3l · Feb 11, 2017

Diamondj421 said:
I did have both hooked up. I read on VintageWindings.com that you have to connect the output transformer the opposite of the input.

If you use 1:1 irons you can hook them up upsidedown insideout. It makes no difference. If you use irons with different windings then youre right.

Next I need to figure out why my damn bypass isn't passing signal.

Which switch you are using?

The fun never ends!

Indeed! But if you have finished the unit and it sounds as you expected you will be happy and go on to next unit

Diamondj421 · Feb 11, 2017

It's the Vintage Switchcraft toggle from Don Audio. It seems simple enough but I followed the first wiring diagram for it on their instructions and bypass means "no signal". Here's the link to the "instructions". https://www.don-audio.com/mediafiles/datasheets/PEQ-Instruction-V1.pdf

Pusch3l · Feb 11, 2017

Try the 2 pole wiring from the last page.

Diamondj421 · Feb 11, 2017

Awesome. And how do I determine the value of that pot for the gain? The Frank schematics call for a 20k resistor and then the PCB provided by Don Audio calls for 5k/10k.