50C5 amp

[baddog]

It probably hums because it desparately needs new filter caps. Does it hum even without the guitar plugged in?

Looking at the schematic, this particular amp with the tube complement that usually is direct off the mains actualy has a power transformer. SO install a three wire cord, and ditch the death cap. (lower left in the drawing.)

Those tubes have to work as a set. I don't mean they are matched or something, but there has to be a 50v power tube, a 35v rectifier, and a 12v preamp tube. SO you can;t really slap a EL84 in it or something. There is not a lot of upgrading tubes you can do. You can replace old worn ones with new old stock tubes. No one makes those types any more, but they were made by the millions in their day. TVs and table radios were full of them.

I think it would be a fun amp to fix up. You probably should change every cap in it. Fortunately that is not very many.

Schematic taken from Schematic Heaven.

I just picked up an old JC Pennies phonograph with a 6c4 , 12ax7 and 2x 50c5 tubes. I recaped the entire amplifier and changed a couple coupling cap values . The little amp sounds great with a guitar although it still has a little buzz. Im gond to use two 120v to 12v transformers to isolate the AC from the chassis and a 3 plong cord.

[Rob55]

Coronette Mystical box

As a reminder I’m an ignorant novice. I have recently acquired a 4” speaker attached to a 2x4x6 chassis with a tube complement of two 50C5 and one 12AU6. You can find pictures at https://plus.google.com/photos/10850...OGJmPH9-7HfogE How did all that get crammed in there? I guess it is true point to point. I assume it is some type or radio receiver.

Rattling a screw driver grounded to the chassis around to everything that looked like a cap brought no snap crackle or pop. I’m just going to tear the guts out. I want to convert it to a low watt guitar amp. One knob, kind of a combination of these two 1-12AU6; 1-50C5; 1-35W4 http://dogbarkmusic.com/Harm/harmony.pdf http://lectrolab.files.wordpress.com...ab_r203_r2.jpg Do you think there is enough room in there?

I plan to use the current cabinet. It is Bakelite. Not too many dials or knobs up front. The tube sockets are riveted in and do not appear scorched or chipped. I know I need to install a 1 to 1 isolation transformer. I think it will fit on top when all those other things are gone.

Assuming the ot and speaker are ok; it seems I can read ohms across the speaker to determine impedance, yes?

I want to put a ¼ out for a speaker cab on the back. Is there one that disconnects and reconnects the internal speaker just by inserting and removing the plug? If yes what is the part #? Where do I find it. I’m not connecting with google on this question. If I use s shorting jack I can only think of leaving the internal speaker in series with the external plugged in.

Thanks for the input.

Rob

I’m sure I’ll have more questions.

[baddog]

Your going to have the same problem I had. No power transformer. These amps are kind of dangerous in that respect so I would probibly pas on that amp and find a small phonograph amplifier that has a power transformer ands nmore traditional tube setup. It would make it allot easier and safer....

Bd

[Rob55]

I've revised and re posted. It will, it will, it will have an isolation transformer. Surely it will.

[baddog]

I have an old phonograph player that has that same setup with the 50C5 and 35w4 tubes. I just havent done anything with it yet. I just had a baby girl and time is tight so I don't think I'll be working on it ant time soon. Let us know how yours turns out when you get it uP and running.