40s Epiphone Electar

[timford]

Hi Guys, my name is Tim and I'm a newbie but long time lurker. I'm getting to the point where I am about to build my first simple amp like a champ (I'll get to that in a later post as I want to do it point to point. I've drawn it up and will ask you to have a look over it for me and make suggestions).

But.... I've come across a 30's Epiphone Electra that I'm thinking of picking up. It is sitting in a shop. It doesn't work at present, and has a broken cabinet that I can easily fix nicely. Really interesting appearance those old prewar amps. I'm interested in a project. Possibly the main salvagable parts will be the cabinet and chasis.

I have not opened up the back yet to see exactly what tubes it has in it. I need to find out its history and how cheap I can get a non functional amp (hoping less than 100). It has the old rola 10" speaker and looks like http://uv201.com/Audio_Pages/epiphone_amplifier.htm When I get the back off I will check to see if the speaker works.

Cloth wiring I can see (from the chassis to the OT) is frayed and exposed. Can't wait to see if there is anything left inside the chassis. Probably never been touched, and not even sure if the tubes would ever have been changed. Not much corrosion on the back of the chassis. Looks like it has been kept inside a house all it's life. USA power (we are 240v) and no earth. I've got a converter that will drop power down to 115V.

I really want to see how the old ones used to be made, and play around with it. Am I mad? Is this where a lot of you got started? Can I get a little help when needed? - I've got a heap of books and played around inside my amps a lot, and done lots of little electronic jobs in the past - but I want to start making some of my own (especially pentode front ends, point to point, low wattage but relatively clean sounding amps).

In your experience, should I do it?

[Cliff Schecht]

I would wait until you get more experience before you go at an old amp like that. Most likely all of the caps inside will need to be replaced (any paper/wax and paper electrolytics will be bad) and many of the carbon comp resistors will be bad to boot. Then you have to test the power transformer under no load to make sure it's safe/stable (applying power with no load, aka cooking the PT). It's also good to test the output transformer either in another circuit or with a multimeter, but the latter won't tell you if the OT is actually good for use with high voltage. You will probably have to clean or replace many of the tube sockets and verify the integrity of the cloth covered wire.

I'm skipping over lots of the details when it comes to repairing and testing such an old amp but IMO it would not be a good project for you to tackle without any prior experience with tube amp repair. Even the simple things like how much solder to use, how hot to keep the iron and how long to apply the heat are things that you don't want to learn on old, sensitive components (a lot of the parts you'd be dealing with are heat sensitive). There's a lot that can go wrong in an old amp and if you don't know what you're dealing with, you can easily wreck the amp (and not in a good way ).

I'm not trying to discourage you, mind you, if you can get a good deal on the amp then by all means get it. But I wouldn't dig into it until you get to a point where you've built a few amps and understand the details of wiring up a power section properly as well as how to actually test/operate on high voltage circuits. The vintage factor really just adds another level of complexity that you probably wouldn't enjoy dealing with if you aren't ready to do so. Once you get a few builds under your belt you will be more familiar with the general procedures and precautions that you need to be taking when working on any amp and you won't have the extra variables of working with parts that may be bad or intermittent.

Edit: Just reread your post and saw you have experience working on amps. I'd still be weary about really digging into the circuit until you have experience repairing vintage amps though. With amps older than the 60's there are parts and construction methods you will be dealing with that are not anywhere near as safe as more modern amps. Knowing how to deal with these is where the caveat lies. If you do pick it up then maybe we can guide you through the process of how to test everything but it probably wouldn't be very enjoyable to flip on the amp after repair and have something go up in smoke and take out the transformers.

[Jack Hester]

Hello, Tim -

I would get real weak, if I had a chance to get an old amp like that. My problem is that I collect for the sake of curiousity.

This may well be the schematic to that amp:

http://www.el34world.com/charts/Schemat ... lectar.pdf

If it is the correct one, that should be an easy amp to do a cap replacement. This schematic is not original, but a redrawn by someone who needed one. It has some modern mods, but otherwise good for troubleshooting.

Which model Champ are you looking to build? I built a 5C1 Champ and a 5C2 Princeton, chassis' only. I'm not a woodworker, so they were just tabletop amps that plug into an external cab. The 5C1 has a warmer tone and the 5C2 is some brighter, but has a tone pot. I like the 5C2 better, as it offers tone adjustment. The 5F1 Champ is a much brighter amp than either of these. Again, just a chassis build. My wife says that all men are boys, and as soon as we conquer something, it goes in the pile with the other toys.

Jack

[timford]

Thanks a lot for the advice guys.

If I can get it really cheap I might get it, and I'll have a look inside, but may be wise to put it aside for a while.

The one I'm looking at is not as old as this one http://prewaramps.org/epiphoneele.htm but has the same looking speaker. So the one I'm looking at is probably 40s. Sounds like the older ones had the power connected directly to the rectifiers with no PT. I didn't even realise this was how they used to do things (see the other epiphone amp with nasty gutshot and description of how it was in the day)

Jack, I'm guessing that the schematic you posted is probably the one, or a close cousin as the amp evolved. I'm trying to find out if it was made by another company and subsequently if it has a more universal 'name/code' and easier to trace schematics. 'Electar' was a pretty broad umbrella. Sounds like the earlier ones were made by the Danelectro man. If I opened it up I would make my own schematic as I've done with my other amps, and as the 'prewar' guy has done with his amps. And lots of good pictures.

I'll probably start off with the 5c1 or 5f1 and learn from there. I'm reading a couple of books at the moment by Merlin Blencowe and Robert Mergantz and I'm getting really excited about testing some of the stuff I'm reading and understanding how it all work. I've got to get practical now, and that means doing something that has been done, before experimenting. And this is the best website I've come across for support and information. And I've noticed there are a few people who build without boards which I want to try (I've got amps of both types that I spend time just looking at the guts, layout and grounding of for reference).

Thanks again for the feedback. You guys are great.

[timford]

Had a good look at it today.

I have not bought it. They want $350

Apparently it worked 10 years ago when it was bought in the US and was then shipped back to australia where the cab was damaged in transit. Apparently the owner was so annoyed he never bothered to try it? I don't buy that one. How could you not test an amp you just bought over from the states in working condition - or at least get somebody to check it over.

It has a 5 pin plug on the field coil speaker. The information I have found so far (with 4pin) indicates that the field coil should have an ohm reading between 700-2k, and I got 1076. There is meant to be a reading between the voice coil and the humbucker of less than 10 ohms and the only other reading I could get from the pins was inconsistently around 350. Wires are exposed in places and could leading to a bad reading. They are bunched firmly in 2 places and it is hard to work out which is which as they are mostly shades of brown. Otherwise there could be a problem that will take some research to fix.

B+ goes to the field coil through these wires and back to the amp and works a bit like a choke between the 2 electrolytic caps. I'm assuming that most of the wire should be replaced by cutting it short to the field coil, rather than patching over with heat shrink in the exposed areas or cutting the exposed wires (mostly the last inch) and reattaching the plug.

There is a bit of dust and crap in the speaker but it looks like it has been kept fairly well otherwise.

Not much obvious rust on the transformer.

Tube compliment is 7A7 loctal (lock in 8 pin) pentode, 76 triode, 2 6v6s and an 80 rectifier.

Chassis doesn't look like it's been opened much. Electrolytic caps are blistered/showing white, and the other caps look greasy and the wax has little cracks on at least one of them. Point to point. Wire looks frail but not fraying from what I could see quickly.

I'm really tempted to give it a go at the right price. Could lose, could win?

But what if it could ever sound like a (noisy) version of this (looks to be completely overhauled including a major polish of the chassis).


http://www.youtube.com/watch?v=MEpaPqzIQc0

[timford]

Nah, just watched the video again, and that one has 3 knobs on the back, and the one I'm looking at has volume and volume only. But this is the only thing I could find that was remotely close (with external reverb).

First job I would have to do is take detailed pictures and then make a complete schematic and let you guys have a look at it.

This is what a 10" rola field coil can sounds like in another old amp when it is overhauled.

http://www.youtube.com/watch?v=_7Iz7gdh ... re=related

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