Valco Bard transformerless amp

[drewl]

This is a weird one
Typical cheap amp from the sixties, 10" speaker and a 6" high frequency little speaker, 35WZ5, two 50L6, and two 12AX7's

Heaters powered by line voltage as usual, taps for the 12AX7 filaments, but it has a high voltage tap going to the rectifier tap
Can't find a schematic, only pix.

I have everything working great and dead quiet, just need to find the right isolation trans
It's a shame, I have a little power trans from an old Radio Shack/Tandy reciever that has the voltages I need, is the exact size but doesn't have the current for the heaters.
It works, but eventually it would melt down.

Don't suppose anyone has seen a similiar schematic?

Question about isolation trans mounting.
I usually have room on the chassis to mount an iso trans, not on this amp.
When you guys mount a trans in the cabinet, do you run the AC power into the amp/fuse first, then to the iso trans out to the amp, or run the ac to the iso trans first, then to the amp?

Thanks.

[Tom Phillips]

When there is no room inside the chassis, I put the isolation transformer in a small project box mounted to the side of the cabinet. Routing of the wiring to the ON-OFF switch and the fuse is dependent upon the situation. I prefer to use an IEC line input assembly with a built in fuse and switch mounted on the project box. This provides a nice clean and safe result provided that proper wiring between the Iso box and the original chassis is properly done.
Please post photos of what you have to work with.
Cheers,
Tom

[Helmholtz]

No matter where located the iso must be fused on its mains input side.
Both the iso and the amp chassis must be safety grounded.
If the amp uses half-wave rectification, the iso must be significantly oversized to safely handle the resultant DC magnetization.