Yeah, I'm a noob. I have a broken amp that doesn't produce any guitar sound.

When I raise my reverb, bass, middle, treble, etc. I get feedback from the speakers so I doubt the speakers are broken.

Any idea of what it could be? My friend said it was the input jack but when I insert one end of the instrument cable in the amp, and rub the other end against my hand, I get feedback.

Note that I do not have a guitar at the moment so I have no way to test it out at the moment.
To me it sounds like your guitar, Unless you have tested multiple guitars on that amp
  • Orange TH30
  • Framus Cobra 4x12
  • Gibson Les Paul Studio
  • Gibson Explorer
  • Taylor 214CE-G
Gonna need more info. Like what kind of amp etc. If its SS and you have tried different guitars and cables in it then its probably time for a new one.