RCA Tube Victrola

[peobus]

I just found an old RCA Victola at my school. Thinking of converting it into a little practice guitar amp. Anyone have experience doing this?

[Regis]

A lot of those old amps have a schematic pasted inside the amp. Pull a panel or the bottom off and see what you have. Also post the tube compliment of the amp, then we can see.

[peobus]

There's no schematic. It has an RCA 25L6GT and some sort of rectifier can with the following info stamped on the side:

943800-4
RED 50MFD 150W.V.
YEL 50MFD 150W.V.
BLACK NEG FOR 75° COPER
472 6039

ON/OFF Volume knob and a Tone pot. I've heard of these things being converted. Thought it might be kind of cool to have kicking around the living room when I wanted to plug in.

[J Martin]

Some of those old phonographs had enough power to drive an output tube directly, but you need another gain stage or two for guitar. A tube that draws the same heater current as the 25L6 is needed like a 6SL7, 12AX7, or a 6SJ7. You may or may not have to adjust the heater string resistor, depending on how present day line voltage affects the voltages. Then there is the fact that the chassis can be live in those amps and presents a hazzard. At the very least put on a polarized line cord to insure the metal work is always connected to the neutral side of the AC line. An isolation transformer is ideal but defeats the idea of a low cost prctice amp. Its probably as much work as building a simple amp from scratch.

[peobus]

You know, you're probably right about the work. The thing looks sooo cool, though. Do you know where I might find a schematic for this thing?

[J Martin]

You can find a schematic through the Sams Photofact archives. That amp is so simple its not worth buying a schematic. I have one sitting in my shop that uses a 50L6. Just turn it upside down in your hand and you can just about memorize it on the spot.

[Steve Conner]

My magic 8-ball says "Watch out, hot chassis"

[peobus]

My magic 8-ball says "Watch out, hot chassis"

Chassis? It's more like and altoid box!

[soundmasterg]

What he means is that it is probably using tubes that add up their filament currents to the wall votlage, and these amps have a hot chassia and are dangerous. If that is how it is wired, then I wouldn't bother trying to make it into a guitar amp.

Greg

[peobus]

What he means is that it is probably using tubes that add up their filament currents to the wall votlage, and these amps have a hot chassia and are dangerous. If that is how it is wired, then I wouldn't bother trying to make it into a guitar amp.

Greg

I got that, Greg. Honestly, I haven't openned it up yet. I swear I've heard of this being done. I let you all know what I find when I take her apart.