Salvaged 2xEL84 organ amp w/ gutshots

[Phil_S]

It might make for an interesting experiment as a cathode bypass. I realize it's value is considerably less than what we typically use, but it might produce some interesting result. If you have an amp with B+ below 200 in the preamp section, you might give it a try. Yes, this one seems to be marked for polarity, so it isn't appropriate as a coupling cap, but others might be "regular" non-polar.

LOL! I've got a small stash of those 200v Goodall caps I harvested from an organ chassis. Someday, I might find a use.

BTW, when you use two caps together as if they are one, you get to add double the voltage rating.

[Firestorm]

Resurrecting an older thread.

Are polystyrene Good-All caps good for anything? This one appears to be polarized (but not sure). It is only rated at 200v, so that rules out most coupling applications.

Probably not polarized; likely just an indication of the outer foil side. A lot of these weird brands (including the Sangamos and the Japanese PIO caps) start leaking their little hearts out after a while, so keep 'em away from oscillator circuits or any blocking/coupling cap applications (the 200V sort of rules that out anyway). Way small for cathode bypass use except in RF land. Maybe something for tone shaping: you could use them in a tone stack if you blocked the DC first (like in a Baxandall); bright switch; presence, etc.

[Rafael]

I bought an organ from a thrift store several years ago for 15 bucks. This was long before I became interested in tube amps. It sort of worked at the time but I had no use for it so I gave it to a friend, whose garage its been sitting in ever since. Tonight I realized it might have some potential as a starting point for a project.

I'm no expert but I am working on a similar organ conversion [Baldwin w/leslie] and from what I can see the main chassis has a power transformer, output transformer, rectifier socket, and 4-9pin sockets, two for the 6bq5 [EL84] Push pull output section and two for the 12ax7 pre, mixer and inverter. Like a few others have suggested, you could gut it and start over, or you could do something similar to what I am doing with an old Hammond amp which is similar in design if not in execution [the chassis is totally different].

What you most likely have is a PP output section, which you should be able to see pretty clearly, with one half of one 12ax7 as an inverter. The rest of the 12ax7 sections are most likely a preamp for the tone section of the organ plus another stage that is used as a mixing stage for the reverb return. With a little work you should be able to convert those sections to gain stages.

One thing I found with my Hammond is that there is a lot of stuff in there that makes sense when you are designing a stable organ amplifier for home use that does nothing for the guitarist looking for the godtone. Things I have hacked out of mine are many bypass caps, the entire feedback circuit around the output section, and all the stuff that supplied the other chassis [all those plugs that the tone section plugged into for example].

Then I had to add some things that make it a useful guitar amp like power switch, fuse, standby switch, volume control, and tone controls.

Now, I have to go and search out some more surplus organs for my experiments.....!