Hi All,
The ST-70 thread on Jeff's "funny car" stereo 70 jogged my memory about something to keep in mind for you guys who are having transformer bells painted, plated or powder coated.
Toroidal transformers are not the only ones that can be screwed up due to improper mounting or enclosing. Your standard EI laminated-core transformer is subject to the same problems--they just manifest themselves a little differently.
If you disassemble a well built transformer, you'll find that there are fiber or plastic washers on the bolts holding the bells on. These are to break the "magnetic short circuit" that would be created due to metal-to-metal contact between the bolts and the laminations. Disassemble a really well built transformer and you'll also find insulating tubes in the lamination bores to further separate the bolts from the laminations.
The point is: when you get your customized bells back from the shop, don't forget to replace the insulating washers when you reassemble the transformers.
Since I receive my transformers disassembled to begin with (the bells are powder coated by another vendor), I can start the assembly from scratch using 304 stainless hardware, aka 18/8, which is nonmagnetic. This solves all the insulating problems completely. As a result, the power transformers run cooler (cold, in the case of the 1773) and the output transformers . . . well, ya gotta be there.
If you can't find 304 hardware locally, McMaster-Carr definitely has it and West Marine possibly does (I haven't checked).