Best way to step down PT secondary voltage

[disorder]

I have a power transformer I would like to use for a "Phoenix" build. The schematic calls for a PT with secondary of 298V. I have a PT from an old Newcomb amp (2 x EL84) that is 335V secondary, loaded. What would be the best way to get the proper voltages for the Phoenix build?

[Jazz P Bass]

Convert the excess voltage to heat?
Edit: Is this a test?

[disorder]

Convert the excess voltage to heat?
Edit: Is this a test?

Not a test, actually trying to make use of this transformer.

[eschertron]

Convert the excess voltage to heat?
Edit: Is this a test?

Personally, I'd convert the excess voltage to SOUND

edit: EL84s can easily take the 335vdc, I believe
increase R1 to lower screen and preamp voltages

[Jazz P Bass]

Not a test, actually trying to make use of this transformer.

Is this not where the BOZ comes in?
(big old zener)

[Steve Conner]

I agree, just increase the value of R1 a little and let it rip.

[Jazz P Bass]

750 /10watt: 750 Ohm 10W Resistor Wire Wound 5% Tolerance 016-750
1000/10watt: 1K Ohm 10W Resistor Wire Wound 5% Tolerance 016-1K

[R.G.]

All of the advice (with the possible exception of make more heat ) are good. Actually, that's what a zener does, anyway.

It all depends on what you want. If you want exactly what the schemo says, you can go to some trouble with bucking transformers and such. I can help with that if you like. A small trannie with two 35-48V secondaries can knock that much off each end of the B+ windings. But it would also have a lot of voltage stress on the secondaries. It would probably work OK.

But I like the idea of just running the output stage at the B+ you get and adjusting the preamp down.

[Bruce / Mission Amps]

I have a power transformer I would like to use for a "Phoenix" build. The schematic calls for a PT with secondary of 298V. I have a PT from an old Newcomb amp (2 x EL84) that is 335V secondary, loaded. What would be the best way to get the proper voltages for the Phoenix build?

[ATTACH=CONFIG]24167[/ATTACH]

Connect a 150ma 5Hy choke to the +DC output of the rectifier first... then the unnecessarily large 50uF@500v filter cap.
A 22uF to 33uF@450v filter cap is probably more then enough.... take all the B+ voltages for the amp from that point on.

[disorder]

Thanks for the all the ideas guys.

Bruce, would I be relying on the chokes DC resistance here to step down the voltage? And also gaining the extra filtering?

I've attached a partial schem of the amp I am converting to the "Phoenix". Would there be any risk/drawback with adding an extra RC stage to the power supply immediately following the rectifier to step down to the proper plate voltage and take all other voltages after that as you normally would?

[jul059]

What about a simple MOSFET with a Zener as shown on GEOFX? Costs about 3$.

[barryman]

did you ever figure this out? building the exact same amp with almost identical PT and trying to figure out how to get the thing to stop fizzing out on me.

[barryman]

Got the fizzing sorted out...stupid me forgot to install the R26 470K resistor. Still going to play with resistor values in R1 as suggested here. Also was told that leaving R1 alone and replacing the 130R with 220R at R12 would do me right as well. Will update with feedback.

[disorder]

Barry would like to hear your thoughts on the circuit. I unfortunately ran into some financial issues so this amp won't get built for another month or so. I'll end up just increasing R1 as suggested here and using decent EL84s.