Wurlitzer 7020 amp to high gain guitar amp conversion

[Nicklsm]

Not one to ease gently into a new project or hobby, I bought a working amp to convert.  Although I have been soldering most of my life, and I work with basic electrical and electronics for a living, I have never tried to build or modify my own circuits.  I have a Marshall DSL40 and a Crate 3112 that I love, but want to do my own! 
Should I just replace all the caps in the existing circuit, or tear out everything and start with the tube sockets, transformers, and chassis?  I am starting with adding a fused 3 prong power cord.  Thanks in advance!

Will need all control knobs, switches etc.

[shooter]

I bought a working amp

Keep it that way for now;
document it, schematic, DC volts
dream of how you want it to sound, find that amp schematic, compare an contrast 

[PRR]

Have you found a schematic for this model? (503?)

If it was *complete*, it might already be a Musical amplifier with high gain and ample controls. But the controls were on the console. And the B+ filtering may use the Field Coil on the loudspeaker.

(Or is this a jukebox amp?)

I love the "matched" 6L6es! It may work fine that way. I once down-rated a 2xEL34 amp and modded to take "any" large Octal. At one point I had a coke-bottle 6550 in one side, a metal 6L6 in the other side. Insignificant differences from EL34 in both holes (some tricks to that.... it was for a school where I knew strange things could happen, had already happened, is why I was down-rating a 60W to a 25W.)

[Nicklsm]

This came from an Organ.  I will have to come up with the tone circuits.  I will have to replace all caps.  Fun times!

[RWood]

I've got one of those, and the Jensen field coil speaker it came with. I haven't done anything with it so I will be following your thread.

I did spend some time looking for a schematic, with no luck. Wurlitzer made a solid state 7020 and there is a schem for that, but it is, of course a very different amp.
They made many organ amp models around that time and some were very similar, so you might get close with something that has the same tube lineup. I stopped looking for one when I realized I would be gutting it and building something else from scratch.

Good luck with yours.

EDIT
Looks like the organ it came from could have been a 4410. Here is a thread on a Model 44 conversion where the amp looks very, very similar..... and there are schematics:
https://el34world.com/Forum/index.php?topic=24391.0

[Nicklsm]

Really looks like a rat's nest in there compared to some others.  I may just start over with it.  Never built something from a schematic diagram before; I DID get into this project to learn...

Thanks for that link RWood!  since all the caps have to come out, I am really considering just tearing it down to chassis, and starting over.

[PRR]

> the amp looks very, very similar.....

If we count "points of similarity" there's almost enough for a conviction on fingerprint evidence.

IF SO.... don't chisel it all out yet!! There's a tremolo very-like Fender's fanciest tremolo (push-pull hi/low filters). The whole power stage needs no re-think, just maybe less NFB for a more open/gnarly tone.

[trobbins]

I can appreciate that the existing circuitry may look far too complex to initially understand, and the suggested changes (from the other thread) also require a lot of appreciation, and I guess that is the advantage of a kit amplifier that starts from scratch with a chassis and a few parts and a 'what to do' guide.  If you had previously grown your experience with a kit amp, then this organ amp would be a good next step to learn about what you've got and what you can do with it.  Even the path of gutting it and trying to then overlay an amplifier on the bare bones can be quite an effort for a first amp.

[1blueheron]

Really looks like a rat's nest in there compared to some others.  I may just start over with it.  Never built something from a schematic diagram before; I DID get into this project to learn...

Thanks for that link RWood!  since all the caps have to come out, I am really considering just tearing it down to chassis, and starting over.

Don't give up the ship just yet!   I was in the same place you are about a year ago with an Allen/Webster organ amplifier that I was about to gut and start from scratch. Sluckey and others persuaded me to hold off and Sluckey walked me through modding it.  I am very glad now that I didn't gut it.  It turned out to be my sons favorite amp.  I learned a lot going through that mod process.

My advice, take tons of digital pictures from different angles of each section before you start so everything is photographically documented before you start.  That way if something breaks loose you can go back and see where it went. Some of the solder joints may be brittle or the wires may break while you are digging around in there re-capping.  Not a big deal if you know where they go to re-attach and re-flow. When you start re-capping, you will find that most of the newer caps are much smaller in physical size. This cleans up the clutter a good bit and gives you more working room as you go.  Also, many of the organ amps had a lot of remote switches, controls, and connectors.  These can also likely be deleted in favor of local chassis mounted pots/switches which will remove more of the rats nest of wires and connections.  Don't pull all of the caps at once and then install new.  Replace each one, one at a time removing the old and putting in the new before moving to the next.  You will be less likely to make a mistake this way. Eat the elephant one bite at a time.

I now have a Wurlitzer 6115 that I just finished gutting yesterday and will be doing a scratch build as I can't find a schematic for it. I did find one for its predecessor in a 1939 Radio craft article which is likely pretty close. 

I will be following with interest.  Your schematic might work nicely for my scratch re-build.

Was this a working pull or is it "unknown"?

[Nicklsm]

Well, before you all had a chance to convince me to leave the circuit intact, I gutted it.  Kinda regret it now, but time to move forward!