I got a hold of this amp, but it doesn't work correctly. When I plug it in, the light turns on, so it's getting power. When I plug in any guitar with any chord, it's completely silent. I looked at the inside, and it looks like it's missing a piece called IC4. This is a Marshall G15RCD. The whole thing looks as though it's been serviced in the past. If anyone could help me, I'd very much appreciate it!
Maybe someone scavenged some parts and tossed it.

IC4 is the power amplifier chip, an LM1875. They're pretty cheap. Here's one for about 3 bucks: