50w Power trans

[Valvehead]

Of all the Fender / Marshall tube amp style 50 watt power transformers youve tested....what is a ballpark voltage at the bias supply from the secondary ? 40-50vac ? With none of the secondary wires hooked up ...no load whatsoever ...

Ive got one showing 10vac bias supply ( Rivera 50w)

[Enzo]

Well, 10vAC makes maybe 14vDC. Is that enough? That is what matters

[The Dude]

A schematic, or even a model number would help. There could be all sorts of things going on- voltage doubler, hybrid/cathode bias, etc. Speculating on this with only a bias winding measurement isn't enough information without seeing the circuit.

[Enzo]

And is it a winding or some taps?

[Valvehead]

[Valvehead]

Rivera Jake model , 2- EL34

[The Dude]

............ and are we sure it's bias supply windings/taps and not for a low voltage supply for some solid state goodies?

[Valvehead]

yes, the 2 OR wires ...

[Valvehead]

OOPs.....sorry guys , 1 goes to gnd. i have 41vac

[drewl]

So what DC bias voltage you getting?

That does seem like it's too low for a pair of EL34's.

[Enzo]

Too low? 41vAC makes 57vDC when rectified and filtered. Seems like enough.

[The Dude]

Enzo, I think drewl was referring to the previous measurement. The two posts above yours are only 1 minute apart, so he was probably typing when Valvehead made post #9.

[drewl]

Yes, so problem solved.

Just sorted out a similar problem on a rare Paragon tube preamp with bad DC filament circuit.

[Enzo]

Hey, I'm old...

[drewl]

Pretty sure we all are.

As I've mentioned before, that's why sometimes it helps to just write out the problem here, which helps the mind find the solution.

Don't laugh, I've even figured out problems in dreams.