vintage tube amps

I have a 1959 VM mono tube amp that I am wanting to use as a guitar amp. My question is there are 4 wires coming out of the chassie one black,one white,one red and one gray. Can I hook the black and white to a power cord ? The wires were hooked to a AM reciever. Can anyone help me hook this up so I don’t get “fried” …

Reported for forum change.

If the wires were hooked to a radio receiver, they are for an input signal to the amp, not for AC power.

A picture would help quite a bit.

I would take the bottom off of the amp and see if I can trace the wires. If two of the wires go to a transformer, then there’s your power input.

sometimes old amps didn’t have a power supply. a multiwire connector came from a power supply to the amp. these were modular systems.

if the power supply was internal two the amp it would likely have two wires for power. the power and signal wires should be well separated in the unit.

amps for home audio systems are not the same as instrument amps. you would likely need additional circuitry to use for something other.

without information like a model number and some electrical know-how on your part it is very possible to fry yourself or the amp.

I’ve heard of people using old radio and phono tube amps for guitar. You need to know how to bleed the charge out of the capacitors to be able to work on it safely. They can store enough charge to ruin your day.

This. Be careful, this stuff can kill you. Know what you’re doing and what components are lethal when improperly handled, or what things might be dangerously foolish, like applying house current to some random set of wires you see.

NO!! In some tube amps there’s a transformer on the output side. It’d tend to be smaller than the power transformer. But as noted above, some tube amps have external ppower supplies & no power input transformer. So tracing wires to a transformer in and of itself provides zero useful information.
glrybnd1: You’ve got something pretty dangerous there & apparently don’t yet have the knowledge to deal with it safely. It’s hard for somebody from modern times to understand just how much casual danger was acceptable in pre-1980s electronics.

Take the thing to a guitar store with a service dept. They’ll get you going right. The alternative is a fire or a nasty shock either now or at some later time. Folks have been killed on stage when they strummed their guitar & grabbed the stand mike at the same time.

Yeah. Some of those old amps weren’t entirely safe even just to use. I wouldn’t screw around with it.

You girls/guys are awesome (not the OP) – I’m just finishing my first semester of electrical circuits (with lab) and popped in hoping I could add some help from the perspective of a regular joe who knows about re-wiring a few things from back before I started playing vintage keyboards, and you guys came out swinging!

This is OT, but not worth starting a new thread – how long can caps (lets say a big old bunch of Farads) stay “armed”? People have told me in the past that you should always be careful around any cap that’s even fifty years old, even if it has had no current for as long. Stricto sensu, is that true?

Electrolytic caps can maintain a charge even after being discharged. Other capacitors will probably be ok once they have been bled down.

To the OP, I’m not sure how much I can help if you don’t know anything about electronics. I assume that a mono amp from the '50s will be a class A tube amp. It may play ok as is, or it could be a great source for parts to make an amp. You might want to post pictures of the chassis and also of the wiring inside.

Probably not.
A big capacitor will be electrolytic, and they have pretty significant leakage. Still, it’s always wise to treat any capacitor as charged.

Now, TV picture tubes are a different story - they are charged to very high voltages, and the capacitor is formed by the metal-on-glass of the tube itself, so they have extremely low leakage, and could store a charge for years…

I sense a formula … I see, … dielectric constant … and … dead people!

Seriously, I didn’t know about paramagnetism in CRT in television sets. Something I can do during break. Thanks for humoring me and all others.

Back in 1985, when I started at the University of Waikato we got a tour of the physics lab. Some postgrads had been playing with a fusion rig (magnetic mirrors, not toroidal). They had a small room full of massive electrolytic capacitors for initiating, including one that had a blown pole. It was sitting in a corner, had been there for years, and is probably still there now. With all the damage, they could not figure out how to safely and completely discharge the thing.