Peavey Vintage

[RWood]

This is a 6 x 10 combo amp with 16 ohm speakers wired in parallel for a load of 2.6 ohms. The schem calls for 4 ohms to the OT.

Power tubes are 4 x 6L6GC and one of them has a short, so I removed the inner pair; it is running on two 6L6s. My questions are:

Does this raise the output impedance to 8 ohms or lower it to 2 ohms? This will determine whether I need to rewire the speaker array.

And with two good tubes am I correct in running these in the outer sockets? They do have an additional 100R going to the screens, versus the inner pair.

Schematic attached.

Thanks,

RWood

ps This is the one that uses a pair of 6C10 in the preamp.

[T9c]

Someone pls smack me upside the head if I'm wrong!!, but I don't believe having 2 of the pwr tubes out will change the impedance at all since the secondary windings of the output tranny determines the output impedance.
It's been awhile since I've worked on amps, but I remember lots of guys having 100w Marshall's with the 2 outside tubes pulled to get that sound at a less than ear-splitting volume (still close though)...
Rick

[Chuck H]

Sorry, I don't make cyber-smacking a regular practice. But since you asked...

If you pull two tubes from a four tube amp it DOES change the secondary impedance requirement. The OT has a turns RATIO between the primary and secondary and that ratio changes when you change the load on either side.

With only two tubes in that amp it wants to "see" an eight ohm load on the secondary. Since the cabinet has six 16 ohm speakers (but is now only putting out half it's power) I would wire up four of them in a series/parellel arrangement for an 8 ohm load...That or get a new quad of tubes and get back all your power and speakers.

I can't tell from the schematic which power tubes (inner or outer) have the 100R screen grid resistors. But it's probably the inner pair. Thats a wierd arrangement I haven't seen before. Depending on how the PCB is layed out, it could be a PITA to rewire it more "correctly".

Chuck

[RWood]

or get a new quad of tubes and get back all your power and speakers.

Thanks Chuck; that's what the owner decided to do, after all. It is good to know what direction the impedance goes in cases like this - I can never keep it straight.

Thats a wierd arrangement I haven't seen before.
Chuck

Do you mean because only one pair of tubes is getting the 100Rs? Or is it something else. Those resistors are on the sockets, tying the inner pair's screens to those of the outer pair. I will attach a picture. The board is a on pcb but the sockets are not.

RWood

[Chuck H]

Do you mean because only one pair of tubes is getting the 100Rs?

Yes. Why bother for two but not all the screens? A better arrangement would look like the drawing below. I wouldn't use the "cement" block type resistors for this only because they're big and clumbsy. Most other wire wound types will "float" on the socket pins with no problem.

Chuck

[RWood]

Thanks; I like that!

[Gtr_tech]

Thats kind of a cool amp....its got potential. Just looking at it from the back I'd assume it was SS front end. Awful sneakey of them to stuff 6C10s inside the chassis. The bad news.....those are getting spendy.

[RWood]

Yes, it might be the first amp to have gone retro in it's styling. After all, it was the early 70s!

A very interesting read was this chapter by Hartley Peavey. Among other things, he mentions the Vintage amp (pg 10) and the 6C10 tube. There is also a later version of this same amp that does indeed use a SS preamp, possibly because of the microphonics that Peavey mentioned.

In this amp one of the 6C10s was replaced at some point by a 6U10. Lower gain ..... and lower cost; I'm not sure what the reason for the swap was. Maybe availability. The owner does want to revert back to the original tube type, though.

RWood

[TomCarlos]

Thanks to all who contributed to this thread in the past. It's an old one!!

I came across the thread because a friend called to ask about the Peavey Vintage amp. One recently came up on the Sacramento Craigslist for $300. It has two original speakers, two brand X, and the remaining two speakers missing. But he was thinking, for $300, it could be a great deal.

And then I found this thread - and the 6C10 tube. (Datasheet attached). Ouch, this tube (if you can find it) runs over $100 each? A 12 pin Triple Triode? And from the looks of it (from the photo in #4, there is no way to easily modify the board to convert this to anything else, I would say PASS!!!

But I wonder if anyone out there decided to redesign the circuit with easily available tubes (12AX7, 12AT7, etc) and use a blank turret board. The other change would be to drill new holes and mount the tubes on the bottom side of the chassis (like the 6L6)? It certainly looks like a simple design (on paper that is).

[g1]

Two of those 6C10's? Too bad. I was going to say to use a transistor for the reverb return and a 12AX7 for the CF and preceding triode, but with the PI and first stage also being compactron, too much work.

Time for somebody to start building adapters for these compactrons (6C10,6K11,6BK11). Two 12ax7 F sockets on a wee board with a male 12pin on the other side. Could have them made up in China for dirt cheap.

[Justin Thomas]

I think I got the last 2 6C10s for a good price on Earth $30/each. Popped em in my 66 Jet in place of those damn 6BK11s.

I'd be willing to rig up something. If I had a permanent home right now. I've made a couple PCB replacememts using turrets & wire & G10. I kinda enjoy the challenge.

I pity anyone with an amp with compactrons AND a PCB. Though 6U10s aren't hard to get or expensive.

Justin

[TomCarlos]

G1 and Justin -

Yes, it would definitely be a challenge project.

Once I wrap up my Class D project (another thread), I might look into seeing how this circuit could be changed to accommodate 12AX7 and a 12AT7 for the reverb. One change I'd make is a single pair of 6L6 output tubes, similar to the the Classic VT. I guess I would also need some help redesigning the power supply for proper voltages. I have seen a video from D-LAB electronics where Terry D converts a Marshall Solid State combo to a Fender Princeton Tube amp using the Marshall chassis and retrofitting components to make a nice tube amp.

I have been in contact with the owner of the amp. He is asking $250 for the amp as it sits. We are way too far apart on this. The only thing I see of value are the transformers and perhaps the reverb tank.

[Chuck H]

Well I think your idea of a turret/eyelet board rewire is fine. These amps will no doubt be bargain bin soon enough because of complications. So for "us" that means a cabinet, mated transformers and chassis for the "nice price" at some point in the future.

[Enzo]

You know there were two versions of the VIntage, the All TUbe, and the hybrid. Both had 6L6 output stages. The hybrid had a transistor preamp. DO we know for sure which version is for sale? Only the All Tube had the 6C10s.

And the tube version is really a pretty simple amp. One could easily remove the board and make a few socket holes and mount three dual triodes, and build it on an eyelet board.

The hybrid version has the 6L6 stages which are no problem, and the transistor stuff would be no issue either.

[TomCarlos]

Hi Enzo....

Yes, this amp has the preamp tubes. The owner didn't know that until I asked him to remove the back panel. He sent me a photo. Just in case it was the Hybrid version, I went searching for a schematic. I could not find one! Maybe the Hybrid was similar to another Peavey amp back in the day?

Anyway, I reviewed an old thread started by Lowcurrent - Peavey VT Classic Conversion. I was looking at his schematic (shown below) and trying to see if I could use that for the Vintage Amp. I am still trying to nail down the voltages on the Power Supply (Before choke, After Choke, B, and A).

I would prefer the Reverb vs the Tremolo. That is why this amp caught my eye.