PY 81 as power rectifiers?

[Mike Watterson]

The transformers have a 230volt primary, 230 volt 330mA secondary tapped at 15 volts, the tapped part of the winding can't be separated..there is also a separate centre tapped 12volt 2A winding.

The tapped 15volt section gives just over 17VAC when running the heater of a PY81.

I've seen old designs that did indeed have the rectifier between the transformer and chassis. Some valve and one was a test instrument with a metal rectifier.

It's also handy if you want a -ve voltage.