Can anyone aid in identifying this amp??

[Resonator Guy]

I just got this little beauty. It wasn't working but I saw the fuse holder was broken, installed a replacement and away it went. It has a 6SL7 , 6V6, 5Y3 tube line-up, no identification anywhere and its logo has perished. Inside, it has a choke and a strangely wired OT in that the output wires go to terminal strips and then to the speaker. It has one of the strangest cap cans in it (see pics). It is a Cornell Dubilier 2x25 mfd 600VDC - 5ngn unit. Never saw anything like it before.It also seems to have an added cap can inside and the old can is still hooked up. It also has one banana jack that may be a later addition as the mounting bolts are crooked.
The thing is dead quiet, no hums or buzzes, but it isn't very loud. I would like to find out more about it before I start replacing caps etc, so if anyone can help, I would appreciate it.

[Chuck H]

I don't have an answer for you. I'm only posting to say that you may not get an answer. It could be a distributor branded Valco or some such. It could be a DIY. It certainly doesn't have a polished look like better amps of the era. That doesn't mean it's a bad amp. It just means it doesn't have the fancy cosmetics of others. That tells me it's likely a contracted piece that was marketed by a discount store. There must be millions of those out there. IMHE even if you DID know the name on the amp you still wouldn't know who made it. Many such marketers sold the same model in different years made by a different company. Unless someone here has one with the name plate and has stumbled upon some info because of peripheral interest and sheer time, I think this one remains a mystery.

That's a rusty transformer there.

[olddawg]

It many not even be an instrument amp. It may be an extension amp for a projector or sound system. The reason the level is low may be because it takes a line level signal. It seems to have just a volume control and both 1/4" and RCA jack inputs which would be consistent with a line level amp. I would try driving it with a preamp and see what happens. Just bring the level ip slowly.

[Enzo]

I see two 1/4" jacks and a RCA jack, I see no bananas. Can't say about all the jacks, but the bulk of it looks commercial to me. The parts all riveted to the chassis would not be a basement build.

I agree it is probably just a powered speaker and so needs a preamp. But that's just a working impression.

Your sealed, oil filled metal cap is a bathtub cap. Here, look at some...
http://www.surplussales.com/capacitors/BathtubCaps.html

[olddawg]

One 6SL7, one 6V6, and one 5Y3... Probably a 3 watt powered speaker.

[Resonator Guy]

Thanks folks. I thought a 6SL7 was a preamp tube. It is in other amps I own. What is it that makes this not a preamp tube here?

I didn't figure I would find out what make it is but it's always worth a try.

I will try it as a powered speaker, perhaps with a surround sound system, just to see if it works better that way.

[Jazz P Bass]

The 6SL7 is probably being used as a preamp.
Something has to drive the 6V6.
That tube lineup, sans 6SL7, reminds me of a Fender Champ amp.
The Fender Tweed Champ: July 2010
The design looks like a prewar Gibson EH-150.
https://www.google.com/search?q=gibs...C_fi4APPnYHIBw

[Resonator Guy]

Yep Jazz, I thought it was a lot like a Champ also, until I saw the choke in there, but maybe I can make it work like one. The light coloured design on the front does look like a prewar Gibson - I wish.
Also, I figured the 6SL7 was a preamp tube, what else could it be, and I am going to review the wiring to see what could possibly be altered to get a little more out of it - - - or I may leave it as is, because it does sound pretty good and I really don't need more loud.

[Chuck H]

The 6sl7 is driving the 6V6. Though the circuit may not be designed to deliver the 6sl7's full gain. I personally think it's an instrument amp because of the racing stripes That doesn't mean it's wired as one right now or that there isn't some other issue causing the low output. One tip might be whether the amp is distorting at low volume or if it never reaches distortion with a guitar level signal.

[Resonator Guy]

Chuck, it distorts just a little when up as loud as it will go, with a Gibson Melody Maker pushing it. I checked other somewhat similar amps I have with different preamp tubes ( 75 Silver-faced Champ, 57 Supro super, 60s Garnet Celebrity) and turned up as far as they would go (never had them that loud before)- any one would blow this out of the room.
I haven't started to trace the wiring on the 6SL7 yet, but probably later today. Then I will compare that to other amps with 6SL7 preamp and see what I can draw out of that.

I just had a good look at a Princeton 5B2 schem. Same tube layout so I will work my way through that.

[Chuck H]

If it's clipping at all that means the output tube is putting out all the clean power it can. If that power seems low it could be due to a poor bias condition, low efficiency speaker, that old rusty OT, very low plate, screen or preamp tube voltage or possibly just an old power tube. Or any combination of these things. I'd trace the circuit and compare it to others to see if it's pretty much a guitar amp. If it is I would just rebuild it and see what it sounds like. If it's not then you can always rebuild it as a guitar amp. If the low volume is due to a low efficiency speaker and/or that old rusty iron you may not get any improvement in volume though. And by the time you're done rebuilding and replacing parts you'll likely be into the amp for more than it's value. I know that's probably not the point or even an issue.

[supawah]

i say GIBSON

If it's clipping at all that means the output tube is putting out all the clean power it can. If that power seems low it could be due to a poor bias condition, low efficiency speaker, that old rusty OT, very low plate, screen or preamp tube voltage or possibly just an old power tube. Or any combination of these things. I'd trace the circuit and compare it to others to see if it's pretty much a guitar amp. If it is I would just rebuild it and see what it sounds like. If it's not then you can always rebuild it as a guitar amp. If the low volume is due to a low efficiency speaker and/or that old rusty iron you may not get any improvement in volume though. And by the time you're done rebuilding and replacing parts you'll likely be into the amp for more than it's value. I know that's probably not the point or even an issue.

i'm fuzzy, and I've owned a lot of amps, I had the exact amp labeled Gibson at one point. I think, I sold it to the guy who was playing with Big Sandy, british guy. anyway, I vote Gibson.

[supawah]

i'm fuzzy, and I've owned a lot of amps, I had the exact amp labeled Gibson at one point. I think, I sold it to the guy who was playing with Big Sandy, british guy. anyway, I vote Gibson.

oh, and mine had a field coil speaker, are you sure that ones not replaced? it's exactly the same except the speaker.

[Resonator Guy]

Chuck, I probably will rebuild it much like the 5B2. Cost may have a little bearing but not much. I really enjoy working on these old amps and don't ever expect to get my money back. It is a great hobby and keeps me out of some trouble.

[Resonator Guy]

Supawah, I am sure it isn't a Gibson. I have a pretty good collection of Gibsons and this doesn't seem like one and isn't in any of the books. That said, Gibson did do many weird things so who knows. This looks like the original speaker and field coil ones are generally larger.