Peavey Donor amp build

[tictac]

The one I posted for you is a "Full Wave" rectified Bias supply. It will have better filtering and be more stable than the half wave stuff everyone is showing you...

It"s the one from Kevin O'Connor Tones of Tone Books...

TT

[dcribbs1412]

tictac
just looking quickly at the image....not sure this is a "bridge" circuit
I could be way off...

Darin

[cbass]

Glad to hear you got the rectifier sorted out.

You could still use the circuit TT is talking about with bridge rectifier.Just take off from the secondarys before your bridge rectifier.

[dcribbs1412]

Glad to hear you got the rectifier sorted out.

You could still use the circuit TT is talking about with bridge rectifier.Just take off from the secondarys before your bridge rectifier.

Thanks cbass
I'm kinda at a standstill with this. Still having a problem getting the bias
to work.And the voltage seems pretty high at 520V. Not sure which way to go
from here.

Darin

[cbass]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

[dcribbs1412]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

thanks for your time
I might give it a try...a little concerned having 520V hit the 22uf 450v caps
So are you saying build another bridge for the bias with the LV taps?

[jelle]

Get caps rated at 550v or totempole a couple.

[cbass]

So are you saying build another bridge for the bias with the LV taps?

Yes.
Or you can buy one for a couple of bucks.The rat shack here has 'em.

[Bob-I]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

thanks for your time
I might give it a try...a little concerned having 520V hit the 22uf 450v caps
So are you saying build another bridge for the bias with the LV taps?

You could do a bridge or half wave like you already have. Adjust the bias resistors until you get the bias in line. 520 is ok for the B+ but you're right to be concerned about the filter caps. The first stage will be fine, but the others may blow, follow jelle's advise and get some 47uf 350v in series with balance resistors.

Sounds like you're really close.

[tictac]

I didn't say full wave bridge... I said full wave.... It's a full wave rectifier circuit with reverse bias diodes...

TT

[dcribbs1412]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

thanks for your time
I might give it a try...a little concerned having 520V hit the 22uf 450v caps
So are you saying build another bridge for the bias with the LV taps?

You could do a bridge or half wave like you already have. Adjust the bias resistors until you get the bias in line. 520 is ok for the B+ but you're right to be concerned about the filter caps. The first stage will be fine, but the others may blow, follow jelle's advise and get some 47uf 350v in series with balance resistors.

Sounds like you're really close.

Thanks guys
I'm going to rebuild the PS board and do as suggested(2 47uf's)
I'll also try a bias circuit using the LV taps
Really appreciate all you guy's time and patience

Darin

[dcribbs1412]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

Wondering if I can just go straight to the bias pot or do I need a cap
first?

Darin

[dcribbs1412]

520 sounds about right.
It will come down once you put tubes in and get it biased

For now if you Use a bridge rectifier on the orange taps you should get about -50volts .Just hook it up opposite of theother bridge for negative voltage.

Wondering if I can just go straight to the bias pot or do I need a cap
first?

Darin

Update
used a 100uf/100v cap and have -55vdc for bias. Set the bias at 35ma
(lowest setting the pot will go) not sure how to get it lower.
498V on plates, I'm thinking this is OK. Have a small reverb whining I hope
is a tube. Amp is running and sounds decent.

Darin

[M Fowler]

Increase the bias adjust resistor. I generally have to increase to 1k.

[cbass]

Glad to see you got it going.