Just learned of this site... here's my current project. Another rusty old PA amp

[va3dxv]

Pics first, I have an album on imgur, hope thats OK: https://imgur.com/a/FsP20

This will be my first ever build and I'm pretty stoked. I've been playing solid state modeling crap, never had a tube amp until recently when I picked this up https://imgur.com/PxhHdUQ and rebuilt the power supply to be quiet/safe, and ended up turning it into this: https://imgur.com/a/YxNl8. Thus begins a new addiction

I tore out the original circuit entirely because I have no idea what this is, no schematic, and it had been butchered badly in places. So I've almost got the chassis and power supply ready to go and I'm not sure what to build. I'm thinking either a Bassman or a 5e3 deluxe... but the octal tubes I have on hand don't really fit with either. I have 2 x 6SF5's, 1 x 6SC7, 1 x 6N7, and 2 x 6V6G-JAN. I have a 6SN7G kicking around also. I'm trying to use the original sockets, pots and xfmrs. the PT works fine, not sure about the OT but it should be OK based on a crude multimeter test... not sure how suitable it will be for the purpose though.

If anyone has any input on this old thing I'd love to hear it! I'll be visiting here a lot as there's a wealth of information.

[jjman]

The impedance of the OPT needs to be determined unless that is marked somewhere. I'd be concerned about potential bass from the OPT but it doesn't look too small and may be fully adequate. You could make just about anything with all those holes sockets available. Are the smaller holes sized for small 9pin sockets?

[martin manning]

Looks like you're well on your way. The dirty red looked like solid rust! Do you want to preserve most of the circuit you have or just a part (power amp, say)? My first inclination would be to keep most of it. I'd get it functioning by putting in some 6L6G's, and replacing bad resistors and leaky coupling caps. See what it sounds like, and trace out the schematic to contemplate the possibilities for modification.

[va3dxv]

The impedance of the OPT needs to be determined unless that is marked somewhere. I'd be concerned about potential bass from the OPT but it doesn't look too small and may be fully adequate. You could make just about anything with all those holes sockets available. Are the smaller holes sized for small 9pin sockets?

Yeah, there's 2 holes that fit a 9 pin perfectly (and I have plenty 12A?7 tubes), but I was really hoping to go with octals and use the original sockets... I'm starting to think I should go that way though since it opens up so many more possibilities. I see so many posts all over the place though, of people saying octals just sound better most of the time... Most of that talk might be voodoo magic stuff, but I don't really have the experience to know

I have no way of knowing what the OT is, I was just gonna try it and hope for the best There's a number on top of the OT that reads "S 3917". It has 3 primaries and 5 secondaries. Only one of the secondary leads is a decent gauge wire, the rest are single or double strands of solid 20ga it looks like. I guess to figure out the impedance, I'd have to feed a small AC voltage to it and read the output voltages, right? Due to lack of test gear, that's about all I can do... I'm using the tubes that were in it when I got it, so I assume it was working at some point with those tubes and this OT... but who knows lol

[va3dxv]

Looks like you're well on your way. The dirty red looked like solid rust! Do you want to preserve most of the circuit you have or just a part (power amp, say)? My first inclination would be to keep most of it. I'd get it functioning by putting in some 6L6G's, and replacing bad resistors and leaky coupling caps. See what it sounds like, and trace out the schematic to contemplate the possibilities for modification.

It's too late the only thing left of the "original" circuit is the filament wires running to the sockets and a few other wires... half the stuff was mouse chewed and the cloth covered wire was so brittle it couldn't be worked with

[sluckey]

Look at some Ampeg schematics. Plenty of examples that use all octals. Lot's of 6SL7 and 6SN7 circuits.

[pompeiisneaks]

Been there, my Tweedle Dee Deluxe was bad, that's how I got to do that transformer teardown video, I think the amp was from about the 40's and hadn't been well cared for... Sad because restoring some of that old stuff is pretty cool.

~Phil

[martin manning]

It's too late

Oh well, it still has a cool look about it. The OT will "work" with 6V6, but the primary impedance for 6L6 is typically half of what a 6V6 would use. That could result in over-dissipation (red-plating). Re octal vs. noval, 6SL7 is pretty much like a 12AX7, and 6SN7 is pretty much like a 12AU7.

[M Fowler]

There are so many cool old circuits one could build into this neat looking chassis. Ampeg B15N or my Leo Fender's favorite the Fender Tweed Bassman 5B6.

I favor 6SL7 over the 6SC7 which are wired differently on the socket. The 6SN7 is good in the phase inverter too.

Most of these old PA amps had 32ohm, 16ohm, 8ohm and 4ohm secondary's on the OT.

Mark

[va3dxv]

...and today I lucked out and found it's bigger, badder, much meaner brother...



This thing must weigh 70lbs...



I'm gonna clean it up and see if it has any identifiable markings anywhere. The chewed up foil sticker on the OT is Hammond I think.

[dorrisant]

Nice project... Just curious, where did you get your inspiration?

[va3dxv]

I've always had more fun making old stuff work than I have taking something out of a box and turning it on. I'm a ham radio guy as well, but recently I'm getting more into playing music and wanted some better sound... but I'm cheap (read: broke-ass white boy), so having lots of contacts with electronic 'junk' around they want to get rid of is a factor also... oh, and, also yours and a few others I've seen online.

[pompeiisneaks]

OOOO someone's got the bug

Congrats on another rescue

~Phil

[va3dxv]

OOOO someone's got the bug

I've got bugs alright.

[pompeiisneaks]

man that leslie sure is gorgeous, would love to hear some samples of it too. I had an old pedal that had a leslie simulation in it that I loved to mess with

~Phil