6G3 power supply question

[lonote]

You might find this chart useful, if you don't already have it. Something I grabbed from somewhere.

[B Ingram]

I've just built myself a 6G3 clone. ...

On the fender diagram, it shows, 333-0-333 into a GZ34, with an output of 375V. ...

Fender schematics are not Gospel. So you can't expect the numbers on them to exactly match the actual vintage amps.
It also turns out that most modern power transformers don't match vintage parts, either, so you don't get what the vintage amp does (but how could one know without having a vintage amp-in-hand to compare?).

I currently own a 1962 Deluxe, and use to have a 1963 Deluxe as well. Overall, these amps used 3 different power transformers, that delivered 3 different power supply voltages.

My 1962 Deluxe uses the 2nd of the 3 power transformers, a 125P17A model.

• With 117vac in it delivers 325v-0-325v to the rectifier.

• The GZ34 delivers 407v to the 1st filter cap, and there is 405vdc on the 6V6 plates (after voltage drop across the OT winding).

• The 6V6s were idling about 25mA.

The filter caps will only charge up to Vac x 1.414 if the rectifier has zero-resistance, if the power transformer winding has zero resistance, if the filter caps are ∞µF, and/or the amplifier's current-draw is zero mA.

• As soon as you're using a tube rectifier and drawing current, DC Volts goes down.

• If you use the small 16µF filter caps of the original, DC Volts go down compared to using more-µF.

• Many modern "clone" power transformer have lower winding resistance than the vintage parts, so their output voltage is higher. Yes the modern parts run cooler (which is probably why the manufacturer chose lower winding resistance), but now the modern part doesn't sag the same way the original did.

Using the PSUD without accounting for winding & rectifier resistance, or amp current-draw, will lead to inaccurate estimates.