Peavey VT classic conversion

[Lowcurrent]

A friend gave me his 70's Peavey Classic, it's the 50 watt 2x12" Vt series. The amp has been sitting under porch for a few years and is rather ragged and rusty. It makes some terrible sounds, but at least the PT and OT work. My plan is to tear out the solid state circuitry and then reuse the chassis, PT and OT. I'd like to add two or three preamp tubes in addition to the two stock 6L6 tubes and build something fun and useful. But I've no idea how much 6,3 v heater current the PT is able to supply. I need 600 mA for two 12ax7's, or 900 mA for three 12ax7's, right? I've searched the web and asked Peavey for the PT's specs, but so far I've had no luck. The PT is for 220 volt and is marked EH-472 695 7611. Does anyone know the specs for this PT?

Thanks!

[Bloomfield]

I don't know the specs but it is likely that is won't have the extra capacity for the three preamp tubes. If there is room on the chassis you could always add an additional filament transformer to run the new tubes; small ones are quite inexpensive. http://www.tubesandmore.com/products...nt-open-63-vct

Andy

[Enzo]

I have a different take. Peavey always used very robust transformers. The two 6L6s need not quite 2 amps, and you are talking about dragging a third amp from it. I tend to thinjk eA from a heater winding won't challenge it. But if this is your project, wire it up with the existing transformer. If it turns out it cannot keep up with the extra tubes, just do what Bloomfield suggests, add a small extra transformer for the extra tube heaters.

[glebert]

I think they used the same PT (# 16732) for the Classic and the Deuce. Since the Deuce was a 4x6L6 it seems like there should be extra capacity there.

[Enzo]

Agree, I just checked.

[TomCarlos]

LC.... does that friend (or do you have another) who might have a throw away Peavey Mace? I believe that amp uses the 705-16733 Transformer. That one should work too. As a standalone part, they are hard to come by on the used market. But as it was suggested, try the transformer that you already have.

If you are a schematic collector, here is the schematic for the Deuce/Mace.

Good luck!!

Tom

[Lowcurrent]

Thank you everyone for your valuable input!
I'm going to take my chances and add three preamp tubes. The plan is to build something based on a 2x6L6 Brownface Fender like the 6G5 Pro, but with only one channel and a one-tube bias modulating tremolo to keep the tube-count down.
I'll post some pics here when I get started (hopefully around christmas holidays).

Thanks again!

Chris

[Lowcurrent]

I found time to start the Peavey conversion this weekend. The amp is from 1976 and it’s not very good looking, but I’m going to keep it looking stock. I’m hoping it will turn out to be an ugly duckling.
I have removed the pcb and other unneccesary parts, installed three noval tube sockets, and started on the power supply. The PT outs out 399VAC, which is a little high. Since there is no center tap, a bridge rectifier is the only option that I know of, but that should result in a B+ of around 515VDC loaded. I’ll put a 100-150 ohm resistor between the bridge rectifier and the reservoir cap to lower the voltage some.

There is no bias tap from the HV secondary, but there is a separate 59VAC secondary on the PT. What would be the best and easiest way to make the negative bias supply?

[DrGonz78]

There is no bias tap from the HV secondary, but there is a separate 59VAC secondary on the PT. What would be the best and easiest way to make the negative bias supply?

Best and easiest is for me!! Just copy the bias supply that was on the original amp.

[nosaj]

Best and easiest is for me!! Just copy the bias supply that was on the original amp.

[ATTACH=CONFIG]56482[/ATTACH]

That would be valid if he's keeping the power section the same. If I remember correctly this particular output on this one is very similar to the musicman output.
It would be very helpful to know exactly you are trying to build. Million ways to skin a cat, but you only need a few ways with the right tool. Give us a roadmap.

nosaj

[Lowcurrent]

DrGonz78, thanks for the schematic.

nosaj, The idea was to build something 40-50 watt brownface fenderish with only one channel and bias modulating tremolo. I used the schematic for the 6G4 Super as a starting point.

[Enzo]

Nosaj, the VTX series was like Musicman, this is plain old grid input. His is a plain old VT series.They used transistors for the phase inverter instead of a tube, but it still fed the grids.

Classic used transistor preamp and tube power amp.

Classic VT used same tube power amp but ICs instead of transistors for preamp.

Classic VTX used the IC preamp and the cathode driven power amp.

[olddawg]

Best and easiest is for me!! Just copy the bias supply that was on the original amp.

[ATTACH=CONFIG]56482[/ATTACH]

Absolutely.. The 6G5 uses -55vdc bias. I’m sure you can adjust the voltage divider to work..

[Lowcurrent]

Well, the amp is up and running. Ended up with cathode bias instead of fixed bias, no tremolo. Yet. Gonna play the amp for while and decide what to do (if anything) with the unused nine pin tube socket.
The amp is quite loud and punchy, and has a raw overdrive when pushed.
Here is a bad example of how it sounds: https://m.youtube.com/watch?v=4S0YDC30etI

[DrGonz78]

Don't see 6L6 with cathode bias too often. Sounds excellent!!! Nice job! You gonna post a schematic so we can see your design implementation?