Sizing an Output Transformer

[Decko]

Hi,

My transformer supplier went dark.

How do you size up the Output transformer?
I need to find a new supplier.

Power section:

2 6SN7GTB's/ 4 6SN7GTB's.
4, 8, 16 ohm taps.

I assume you need to calculate total current draw and apply a safety factor.

I am sure there are more specification to qualify.

What are those?

Note: I have qty 1 output transformer/ and 1 power transformer from my previous supplier.


Regards,
Decko

[ChrisM]

For the same results/product send him the old iron and let him reverse engineer them. Give him as much info on them as you can.

[Decko]

Hi Chris,

Thanks. The OEM is Heyboer but the supplier was from a guy at AX84 who had these custom wound.

I guess I could call Heyboer...

Regards,
Decko

[Structo]

Yes call Heyboer but they may not divulge the specs of a custom transformer due to confidentiality.

Can't you use an off the shelf OT?

Just find a similar amp and use those specs.

[katopan]

You can copy core size from the existing one. Primary impedance and max current come from datasheet examples or load lines. But a pair of 6SN7s in push pull is often sized with a 20k OT rated for 2W or more. A quad needs 10k at 4W. Does the existing one have taps for the pair/quad or do you mismatch the output load? I think I remember MPS has a 20k 2W OT. But a 4W one is pretty custom. Although a 5W line PA transformer would work alright.