Epiphone Century

[rafe]

I picked up an Epiphone century today it is missing the tremolo tube, the schematic calls for an 6sq7 but this is wrong as the amp never had an octal socket (anyone know the tube they used?) or the equivalent Gibson model? It has a 15" Jensen alnico with a "7" year date, but I believe it's a newer replacement. I think the amp is an early 60ish It has had the electrolytic's redone at some point.... and a 3prong that is iffy at best .....I am going to redo that. the polarity is still wired in the circuit, and the death cap is on it (Not Good) I'll bypass that switch ....Thanks for the tube info in advance , It's actually a different preamp tube line up than the schematic 6eu7's and a 5879....i think it might want a 6eu7 for the tremolo?

[shooter]

the amp never had an octal socket

6EU7 is a 9 PIN wired NOT like 12XX7

[rafe]

6EU7 is a 9 PIN wired NOT like 12XX7

Besides the heaters pins 1&2; only 4,5,& 6 are wired .....1/2 of a 6eu7 would only make sense

[AlNewman]

Show the schematic of your amp.

[mresistor]

Read this it answers your ?   https://themusicemporium.com/products/epiphone-ea-25t-century-1961

[rafe]

Show the schematic of your amp.

This is the only schematic I can find of the epiphone century, the tube lineup is not the same as my amp. The one with the ? mark is missing the two crossed out are 6eu7's in mine ....I am pretty confident the missing tube is going to be a 6eu7,but I'm not 100% sure.....The socket is wired indicating the same pin wiring as 1/2 of a 6eu7.....The next question would be can I trust the rest of the schematic

[shooter]

to quote a previous President; "Trust but VERIFY"   

[SEL49]

The next question would be can I trust the rest of the schematic

You're in the best position to answer this question. Trace the amp wiring to see if it matches the schematic.

[rafe]

   Mr.Resistor: There you go....That verifies it. I wonder if they had a supply of earlier 15' speakers, if the speaker is original P15R it's dated the 42nd week of 1957, one of the 6v6's is a 1961 Gibson badged Raytheon (NICE) Always wanted a ga-20 .......what a shocker lol Thanks


Sel49. Yes that is true, however I am starting to think it would be, It hasn't been molested other than electrolytics .....so I'll be checking the values of the original resistors .....and compare them to the schematic Thanks

[bmccowan]

I am pretty confident the missing tube is going to be a 6eu7,but I'm not 100% sure.....The socket is wired indicating the same pin wiring as 1/2 of a 6eu7.....The next question would be can I trust the rest of the schematic

I have repaired several Gibson and Epiphone amps from that era and I think you are right about the 6eu7. They are found throughout both lines of that era.
My guess on the 15" speaker is that Gibson had been making a lot of accordion amps with 15" speakers. As polka music faded they needed homes for those speakers. But its just a guess. Nice speaker for sure.
Can you trust the rest of the schematic? In my experience, no. But any differences will not be huge: resistor and cap values mostly. It seems the attitude in the shop was "can't see it from my house."
They can be hard to work on, but sound great once serviced.

[rafe]

I sorted out the 3 prong cord leaving the polarity switch unused (for now) Both the 6v6's are 1961 Gibson branded Raytheon's I, I found a G. Brit. 6eu7 and put that in the first position and moved the tube it replaced to the tremolo. It's funny how I decided not to fire it up until I fixed the 3-prong set up ....Which was totally insane. One of the speaker wires was connected by 1 yes One strand .....PO said it worked (One Strand ???) any way I discovered it when I needed to remove the chassis. Yes, the mahogany footswitch is with it and connected. The 9 pin sockets had rubber grommets that are pretty well gone....I will address them at a later date. I left it in the shop as the only thing needed is to resecure it in the chassis (Need extra hands and or patience to do that) and re-solder speaker.....This is my start on revisions on schematic

[bmccowan]

That's a pretty unique amp you found. Good luck with the rest of the project.

[bmccowan]

And two things:
 - attached is a schematic of a Gibson from that era that uses a 6eu7 as the oscillator tube - it might be useful.
 - Those rubber grommets on the tube sockets are one of the nicer things Gibson did. Their typical use of pentodes in the preamps stages likely led to that. I have found suitable replacements searching through good hardware stores; O-rings, rubber gaskets, etc. Depending on what you use, you can't tighten them down too much, so a little Loctite on the threads helps keep things together. The originals are probably riveted, eh?

[rafe]

1961 Epiphone EA-25T Century | The Music Emporium


Mr. Resistor post this article and it cleared everything up. They made tube changes to the century amp ....I'm pretty confident that the schematic I posted is correct or at least very close with possible  value differences. Yes the sockets are riveted and will need to be addressed further on down the road .....I put it back together and I think this is the best amp I own. Dead quiet and two distinct channels ....vibrato on the second channel  eewwwww it's good. ....This is  a GA-20 in it's best form IMHO

[rafe]

All original except the electrolytics Spragues) and the burlap grill cloth ....I had to put new feet on it too

[bmccowan]

1961 Epiphone EA-25T Century | The Music Emporium


Mr. Resistor post this article and it cleared everything up. They made tube changes to the century amp ....I'm pretty confident that the schematic I posted is correct or at least very close with possible  value differences. Yes the sockets are riveted and will need to be addressed further on down the road .....I put it back together and I think this is the best amp I own. Dead quiet and two distinct channels ....vibrato on the second channel  eewwwww it's good. ....This is  a GA-20 in it's best form IMHO

No need to gloat - I was already jealous. That amp is almost like having a GA-20 and a GA-40 (5879 preamp) in one chassis. Very cool. I have two versions of GA-20s and two of GA-40s - one would think I'd be happy.
I think you are right on the schematic. I posted the 25rvt schematic because it was an example of Gibson's use of 6eu7s.

[rafe]

GLOAT? Greatest Luck Of All Time, I met up with a guy 1/2 way 30 mile trip to buy a Lesmann 500 accordion amp.....which is compared favorably to a fender pro tweed. I grabbed that ....He happened to have the epi with him to show a friend of his. I didn't know the half of it, but I knew it was worth $50 more than he was going to ask from his friend. I will have a lot of ?'s on the Lesmann, as there are no know schematic .it's a 1960 15" alnico that specs out very close to the pro and is very high quality .......

[bmccowan]

As luck would have it, I also have a Lesmann 500. I bought it a few months ago and have not yet touched it. I think I located a schematic - I'll check. I agree that is similar to a Pro and is very well built.

[bmccowan]

Here it is

[rafe]

We seem to be on a parallel amp journey, I looked everywhere for a schematic  may you find a 61 century......The 500 I have seems to have been worked on Nothing added but there are 2 sockets to nowhere .....i'll study the schematic, but Ima be playing the century for a few weeks nonstop before i work on it lol

[rafe]

It might be a little different schematic but not where it will affect me ....on the bottom left is a socket that I think is an output to a transformer to an accordion, My amp has two such sockets,,,,,,If you check e-bay right now there is a Lesmann 500 amp and accordion for sale and there is a pile of cords with boxes that go with it. at first glance I thought there were two tubes missing on mine but the wiring disproves that . Also  Uncle Doug worked on a different model Lesmann and the transformer was built in ....you need a pretty big step-up to hear the transducers in an acc. and organ ....if you get a chance look to see if you have one or two empty sockets under the skirt of yours ....Thanks and regards....Mine is functional and sounds good for guitar so I'm thinking
 someone did something ....I'm not sure what yet. But i'm getting a weird swooshing on the pots and I think it's bad caps ....one is an old wax, and it's got to go
<E-BAY

[bmccowan]

I'll check - it won't be for a few days as it is at another property.
I set it aside when I got it and have only peaked at the chassis. What I gather is that the amp and accordion were a matched pair. The accordion is electronic and gets it's power from an amp interconnect. There was also a DeArmond expression pedal. So at least one of the sockets you see carries high voltage - careful of that!
In the meantime, here is another one on Reverb - better description and it has the same schematic:
https://reverb.com/item/59340640-lesmann-imperial-500p-accordio-organ-amplifier-1966
And a project blog with some interesting info:
https://judyboxamp.blogspot.com/2017/04/the-lesmann-amplifier-project.html
And discussion threads:
https://www.tdpri.com/threads/psa-an-oddball-amp-you-should-not-dismiss.889958/
https://bb.steelguitarforum.com/viewtopic.php?t=318830&sid=82453800b79302bb2f4a6a11bb105512
https://www.tdpri.com/threads/my-new-fargen-lesmann-tweed-bandmaster.1152581/
https://surfguitar101.com/forums/topic/18865/

[rafe]

Mine is the one in the second link ....the only difference mine has two inputs and that one has an input and a switch, I believe mine is original two different channels .....  I have a 1960 ....it looks like the 500P underwent a few changes. The lettering is mostly gone on mine and a couple pots have illegible tape markers on them ....I don't know yet if the were modified or not. I need to fire it up again as I assumed both inputs were like a fender (the same) so I need to check again. I also need to take a closer look for any obvious (or not so obvious) mods ....It looked pretty unmolested at first glance ........Thanks for the links , I had found some of them but not all ....I also have a Dearmond volume pedal from an earlier purchase .... l'll probably start another thread when I deep dive on this