TAD 150 Pre Amp transformer died

I would replace with the same style they had.... Torroid.

Not sure if they're still around but did you attempt to contact Audcom?

Sounds like Audcom is no more.
I heard years ago the factory closed (maybe burned down ?).
One dead end after another.
Hate to end up selling this for parts...

No need to sell for parts any good repair place will simply replace the tranny with one spec'd accordingly.

What area to do live? Goodness even I could do this simple job. You can get your pre fixed for sure.

I'm in Tampa. The stereo repair shop I took it to
couldn't find anyone that could make a replacement (≤$400 anyway),
as the machinery to make toroid transformers is apparantly very expensive.

As it stands the only option is to send the blown transformer to
Mercury Magnetics and hope they can make a comparable CI version.

But I'm happy to pay you, Grannyring, if you can do it.