The AM Forum

I've polished the chassis best I can.  Since I don't have the cabinet, I decided to make my own to save 8+" of rack space.  Components including the sockets and switches are in remarkably good condition.  I'm beginning to mount them as I clean them.  I've decided to repaint the power xfmr, so as soon as that dries, I'll start working on the power supply.

Dumb Question Time: Heath shows the filament circuit with one lead grounded.  I'd rather go with a twisted pair.  Is there any advantage to running a twisted pair?

Twisted is good if any audio is around, but maybe it does not matter in rf circuits.
I always did twisted pair where I could.
Some RF stuff might like a very short path to ground, even on isolated filament tubes...

Not for RF work, twisted pair is usually for audio circuits.  Twisted pair filament wiring in RF circuits would probably cause problems.  It is used in low level audio circuits to keep ac currents off the chassis.

 I have a cabinet for the AT-1 hanging around.  I'll check the thing out to be sure it's from an AT-1 and let you know.

Fred

I've always used a twisted pair for audio but wasn't sure about RF.  Now in looking through some handbooks, most of the filament supplies show one side grounded.  The exceptions seem to be in amps, but they have separate xfmrs with a grounded center tap.  Fred, if you have a cabinet for this animal, that would be fantastic!

Mike