Peavey Donor amp build

[Bob-I]

Oh, and lose the cap C1

[dcribbs1412]

Cap off the low voltage tap and connect only the high voltage tap to the bridge rectifier. Nothing from the PT secondary taps get grounded.

Will do Bob..and report back
Thanks

Darin

[dcribbs1412]

Cap off the low voltage tap and connect only the high voltage tap to the bridge rectifier. Nothing from the PT secondary taps get grounded.

Ok when I cap the high voltage CT tap(R/Y wire) I get nothing on the bias.No sound
when I ground the HV CT tap amp works but I only get 250V
any suggestions

Darin

[Bob-I]

Cap off the low voltage tap and connect only the high voltage tap to the bridge rectifier. Nothing from the PT secondary taps get grounded.

Ok when I cap the low voltage tap I get nothing on the bias.No sound
when I ground the LV tap amp works but I only get 250V
any suggestions

Darin

Just to be clear, you should have the lead from the fuse to one side of the bridge, the red (hi) lead to the other side, the bridge ground is is solid and the B+ leadnshows nothing?

Measure the AC across secondary leads.

[dcribbs1412]

Bob
appreciate your time
not sure I'm following you
here's a pic of what I have now.... 2 Red HV taps to diodes splits to bias
R/Y CT is to ground with filter caps
380V across leads

[Bob-I]

Ok, that's a full wave rectifier, not a bridge.

Double check the schematic.

[dcribbs1412]

Ok, that's a full wave rectifier, not a bridge.

Double check the schematic.

Thanks Bob
I'll do some research and see if i can wrap my head around a bridge
I gotta say the amp sounds decent as is, but I know its not right
bummer to stall so close to the end.
Thanks for your time

Darin

[cbass]

If I remeber correctely on these transformers you can use a bridge rectifier on the orange taps to get around -50vdc for your bias.

http://www.hammondmfg.com/pdf/5c007.pdf
This link may help clear things up

[dcribbs1412]

If I remeber correctely on these transformers you can use a bridge rectifier on the orange taps to get around -50vdc for your bias.

http://www.hammondmfg.com/pdf/5c007.pdf
This link may help clear things up

Thanks cbass
I'll need to figure out which to use...I do have a choke on this build
was hoping to use the orange taps down the road for relays.
Appreciate your time

Darin

[cbass]

You'll want to use the full wave bridge capacito rinput.

Third one down on right

[dcribbs1412]

You'll want to use the full wave bridge capacito rinput.

Third one down on right

Got it... I have 520V now but the bias went wild.Wondering if a change
of resistor value up from 56k to say 220k would work.Or I need to rework the bias circuit like a marshall (jcm900).

Darin

[Bob-I]

You'll want to use the full wave bridge capacito rinput.

Third one down on right

Got it... I have 520V now but the bias went wild.Wondering if a change
of resistor value up from 56k to say 220k would work.Or I need to rework the bias circuit like a marshall (jcm900).

Darin

Glad to hear you got it. Yes, try the 220k. You could get crazy and calculate the voltage divider values, or you could swap the resistor and take a wag.

[dcribbs1412]

You'll want to use the full wave bridge capacito rinput.

Third one down on right

Got it... I have 520V now but the bias went wild.Wondering if a change
of resistor value up from 56k to say 220k would work.Or I need to rework the bias circuit like a marshall (jcm900).

Darin

Glad to hear you got it. Yes, try the 220k. You could get crazy and calculate the voltage divider values, or you could swap the resistor and take a wag.

Thanks Bob
I'll try a 220k and see...I feel I'm getting closer
do I need a blocking cap?
thanks for your time

Darin

[ToneMerc]

Darin, I knew I had this somewhere, it used to be available on the Torres site. This makes a good general reference for when you need a make bias suppy from the HT winding.

TM

[dcribbs1412]

Darin, I knew I had this somewhere, it used to be available on the Torres site. This makes a good general reference for when you need a make bias suppy from the HT winding.

TM

Thanks TM
much appreciated

Darin