Vintage Epiphone combo

[andresound]

Pulled the trigger on this yesterday. Still need to collect. It was owned by an 80 year old widow. 1961 Epiphone EA-10RV, 1x 15 inch combo. Unit works and seems to have the wrong output tubes (looks like a 6L6), but one is missing!! and recto (looks like a GZ34). Some work has been done in past.

Any info would be appreciated, I.e. Schematic etc.

If this is a PP (25w with 6v6's), how can it still produce sound from just one output tube. (I requested a video demo), Or has this been modified to SE?

[Stevem]

I could not find a schemstic for it on line , but I will look thru my stack over the weekend for you.
Seing as the amp has a 15" driver I would take a educated guess that 6L6GC tubes are correct for the amp and I can see that it is a Cathode biased output stage.

I can also see that the 2 yellow filters and the Orange one still need to get swapped out for new ones!

The amp can play with just one output tube and will do so in almost a Class A mode until a high enough volume is reached and then it will distort and really sound like crap, but that being said you should not really have it on with only 1 output tube in it as both the filament voltage and the amps DC voltage level will be a tad too high without that other tube in it.

For now it would be better to run it with two 6V6 tubes than just one 6L6.

That's a nice find and I bet you will love it when it's up to snuff!
Oh, also that speaker if it's still good is worth over 200 bucks all on its own!

[martin manning]

That is an odd one. I think it is basically an EA-10 Deluxe, which does have a GZ-34 and 2x 6L6, plus one more tube for the reverb. A p-p amp will make sound with one output tube missing, the output waveform is just clipped on one side when the remaining tube cuts-off.

[sliberty]

I have the scheme for the EA10 Deluxe, and will post later.

[martin manning]

Link to EA-10 Scheme: http://bmamps.com/Schematics/gibson/ea_10-deluxe.pdf

[M Fowler]

I love old combo amps and this one looks like fun.

Mark

[sliberty]

Link to EA-10 Scheme: http://bmamps.com/Schematics/gibson/ea_10-deluxe.pdf

Well, now I don't have to :

[andresound]

Thanks for info guys. Martin Thank you for the schem. On epiphonewiki.com there is reference to a Delux EA10 and EA-10VR. Both are listed at 25w, 2x 12ax7 + 1x 12AU7 (PI), 1x 5AR4 and 2x 6V6. I don't know what tube would be used for the reverb of the RV model.

I do not want to risk local couriers, so I will probably only have the amp in my grubby paws in about a month when I get a friend to transport it the needed 600km.

Looking forward to this project. Will keep searching for a Schem that includes the reverb circuit.

Will post soon

[Firestorm]

If epiphonewiki is correct about this wanting 2x6V6, this probably matches closely to the BA-15RV, but with a 15" speaker and 12AX7s instead of 6EU7s. PI is cathodyne, so the reverb is driven off half a 12AX7 (V2b maybe) and recovered with other half of the 12AU7. According to Blue Book, Gibson only shipped 76 of that model during its lifetime from 1961-1963, so it's a rare bird.

[andresound]

This is what I have found. Apparently, only 76 units were shipped of the RV model

[andresound]

The RV model I have, has 4 pre tubes.

[martin manning]

The Wiki page seems to confirm that the EA-10 and EA-10RV are basically the same amp save for the reverb. Note the Wiki says "2x 6V6GB," a type which never existed, AFAIK. The EA-10 schematic shows 6L6GB, which is more likely to be correct.

I think Firestorm is onto something with the BA-15RV, though. It uses a 12AU7 cathodyne PI, which would free up half of the EA-10's paraphase PI tube to drive the tank. The 4th tube in the EA-10RV would then probably be a 12AX7, with one side feeding the 12AU7 reverb driver and the other for the reverb recovery as shown in the BA-15RV.

What I would do is look at the PI and see if it is a cathodyne (and in the picture you posted it looks like it is), then trace the rest of the reverb circuit out for yourself and see if it matches the BA-15RV.

[andresound]

Thank you Martin. This will be my first experience with this type of PI and a reverb circuit. So some research and learning is on the cards.

[martin manning]

It'll be an interesting ptoject for sure. To confirm the output tube type, measure the OT primary impedance. For 6L6 it will be around 4k, and for 6V6 it will be around 8k.

[Phil_S]

I am thinking the schematic is somewhat similar to the Gibson GA15-RVT. Ignore some of it that doesn't fit. Structurally, I'm thinking the number of tubes, etc. It might give some helpful hints.