Toroidal transformer help needed

Bart_J86 · Jan 21, 2022

So, I am building a Neve 1073 pre/eq clone including its PSU. For the PSU I received (as part of the diy body kit) a toroidal transformer, without a brand name, type number or any data sheet. The only info given is pri: 115v white, 115v black. Sek: 18v red 18 blue, 50VA. So I’m quite confused on which leads are live and which ones are neutral. I will post some pics down here.

Could anyone please help me to identify the live and neutral wires? Or is this of no importance because all are relative until you connect one of them to neutral on the pcb/power plug?

Whoops · Jan 21, 2022

I don't think it makes a difference but I would connect Live to White and Neutral to Black

Toobme · 2025-01-21T21:53:40-0500

@Bart_J86 Did you get this sorted?
I have the same transformer (but 25v secondaries).
Would be curious to see what you ended up doing.
Cheers

Bart_J86 · 2025-01-22T01:18:35-0500

Toobme said:
@Bart_J86 Did you get this sorted?
I have the same transformer (but 25v secondaries).
Would be curious to see what you ended up doing.
Cheers

I don’t know how to insert images in a reply to your message, but I’ll try to explain what I did. When looking at the transformer with the primary leads on the right and the secondary leads on the left, I connected it as follows (thanks to the directions of the seller):
- Right white primary lead to the live tab of the plug;
- left white and right black primary lead connected;
- Left black primary to the neutral tab of the plug;
- Ground tab of the plug to the top (screw) of the transformer;
- right red secondary lead connected together with the right blue secondary lead to the right ac connection of B1 rectifier;
- left red secondary lead connected together with the left blue secondary lead to the left ac connection of the B1 rectifier;
- ground connection of the B1 rectifier to the top of the transformer (screw), (so together with the ground tab of the plug)

I hope this is a clear enough instruction. If not: please teach me how to post a picture in a reply and I’ll show you the connections I made.

Toobme · 2025-01-22T16:14:21-0500

Thank you very much, @Bart_J86 - I’m assuming you are wired for 240V from the house?
I’m doing 120V so, will do your schema, but with whites tied and blacks tied together for parallel.

Your explanation of the secondary side of things is even more helpful - thank you again!

For photos, I just click on the little icon above the text field (the one I’m writing in right now), that looks like a little picture of a mountain with a dot for a sun. If you’re not getting the WYSIWYG toolbar at the top, try using a different browser maybe? I’m not sure. But the adding of photo/video media as well as bold, italics, and color appear at the top of the reply field for me.

Or it may be a limited option until you post a certain number of messages - maybe? Not sure.

Bart_J86 · 2025-01-22T16:36:54-0500

Toobme said:
Thank you very much, @Bart_J86 - I’m assuming you are wired for 240V from the house?
I’m doing 120V so, will do your schema, but with whites tied and blacks tied together for parallel.

Your explanation of the secondary side of things is even more helpful - thank you again!

For photos, I just click on the little icon above the text field (the one I’m writing in right now), that looks like a little picture of a mountain with a dot for a sun. If you’re not getting the WYSIWYG toolbar at the top, try using a different browser maybe? I’m not sure. But the adding of photo/video media as well as bold, italics, and color appear at the top of the reply field for me.

Or it may be a limited option until you post a certain number of messages - maybe? Not sure.