PT salvage

[riz]

I have here a cute little servo amp chassis, originally 2 x 12ax7 and 1 6v6. I have a little SE OT laying around so obviously I wanna make something with it! The PT is labeled primary: 117v AC secondary: 240-0-240 @.70ma DC, center-tapped, with a 3A 6.3v secondary as well. Thing is, there's only one red secondary wire and the CT coming from the end bell, and it goes to what looks like a half-wave rectifier, so they used it this way originally. The end bell seems pretty stuck on there, but it doesn't seem potted, can I just pop it off with a little force, or is that a bad idea? I'm hoping that the other red wire is in there. I've never popped end bells before, I know they often are made to come off, just thought I'd ask as I'd hate to make this scrap iron. Guess I could always build a little Fender-type reverb with it, that's half-wave rectified... I was hoping to make a Champ-thing with it and give it to my buddy for playing around the house. Any reason a simple little SE amp won't work well with a half-wave rectifier if I can't find the other wire?

[Tom Phillips]

Removing Transformer End Bells

If you are careful it's OK to remove the end bell to take a look inside. They are often stuck to the laminations by the transformer varnish. In those cases I have good luck using a utility knife as a wedge between the end bell and the lamination if the transformer doesn't come apart when the screws are removed. Be sure to keep track of any insulating washers and sleeves that may be on the bolts. Those parts help keep the bolts electrically isolated from the laminations. There may also be an insulator between the end bell and the windings. And sometimes there is a bare wire pinched in between the lamination and the end bell. If so, it is the connection to an electrostatic shield.
Regards,
Tom

[ThermionicScott]

If you hook up the primary to wall voltage, you can figure out if the half wave rectifier is using the whole secondary or not. Nothing wrong with half-wave rectification, you'll just need more capacitance to smooth out the DC, as compared with a full-wave.

-Scott

[riz]

Thanks guys, my hunches are bolstered! Maybe I'll look into using a 6k6, I found a few in my grandfather's garage.