Peavey Electronics Power Transformer - Peavey Bravo?

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absolute ape
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Peavey Electronics Power Transformer - Peavey Bravo?

Post by absolute ape » Mon Jun 28, 2021 12:16 pm

Hi everyone, I have a Peavey PT that I can't seem to find any information on. I've emailed customer service but they never got back to me. It's labelled 705-18785. I've heard elsewhere that it may have originally been in a Peavey Bravo. If anyone can tell me anything about this PT, especially tech specs, it would save me a lot of hassle.

Thanks guys

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Enzo
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Re: Peavey Electronics Power Transformer - Peavey Bravo?

Post by Enzo » Mon Jun 28, 2021 9:20 pm

That is indeed for the Bravo, 120v version.

As far as I can tell, the red wires would be for high voltage. Drawings do not report voltages, but I'd guess around 250vAC which would make a 350v DC B+. You can measure it.

There is a 6v winding for tube heaters, fused at 4 amps I'd guess good for maybe 3A.

There is a low voltage center tapped winding for the preamp tube heater, relay, LEDs and bias supplies. Looks like about 20-0-20vAC, which will rectify and filter to about the 27v on the schematic. Probably good for a couple amps.

absolute ape
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Re: Peavey Electronics Power Transformer - Peavey Bravo?

Post by absolute ape » Tue Jun 29, 2021 9:36 pm

Enzo wrote:
Mon Jun 28, 2021 9:20 pm
That is indeed for the Bravo, 120v version.

As far as I can tell, the red wires would be for high voltage. Drawings do not report voltages, but I'd guess around 250vAC which would make a 350v DC B+. You can measure it.

There is a 6v winding for tube heaters, fused at 4 amps I'd guess good for maybe 3A.

There is a low voltage center tapped winding for the preamp tube heater, relay, LEDs and bias supplies. Looks like about 20-0-20vAC, which will rectify and filter to about the 27v on the schematic. Probably good for a couple amps.
Hey, thanks. I will have to measure it, but I was hoping to get a spec sheet or something. Anyways, I don't have any alligator clips since my multimeter didn't come with any and I'd rather not be poking around in the amp with both hands. I'll have to run out and get some proper leads or what ever.

The amp is an old Traynor and your prediction seems a little low for what this amp wants to see which is slightly worrying. I think the amp's original transformer was more like 300VAC. Again, I'll have to measure

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Enzo
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Re: Peavey Electronics Power Transformer - Peavey Bravo?

Post by Enzo » Wed Jun 30, 2021 2:20 pm

It was just a guess. I picked 350vDC for the Bravo B+. It could easily be 400v, I have no idea.

absolute ape
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Re: Peavey Electronics Power Transformer - Peavey Bravo?

Post by absolute ape » Sat Jul 03, 2021 12:53 pm

Enzo wrote:
Wed Jun 30, 2021 2:20 pm
It was just a guess. I picked 350vDC for the Bravo B+. It could easily be 400v, I have no idea.
Cool, thanks a lot

tedmich23
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Re: Peavey Electronics Power Transformer - Peavey Bravo?

Post by tedmich23 » Thu Jan 25, 2024 1:32 pm

For the now ancient historical record Enzo (as usual!) was correct. The Bravo power transformer puts out close to 300VAC which results in a B+ of almost 420VDC!
This is pretty high for modern EL84s especially since its parallel axis geometry (PAG) keeps its EL84s toasty hot! (Fan was a kludged addition no one likes) 340-360VDC for a B+ is more reasonable for modern EL84s and there are some alternative PTs that will do this (Edcor has some). The bias and heater supplies (22VAc and 6.6VAC respectively) are harder to spec.

A simple way to try lower B+ could be a MOSFET/zener voltage dropper; many kits are available that do this.

There is also a pad for a bypass cap on V2a that can be included in the switched V1b boost circuit if you're daring...

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