[Clueless Newbie]

Received a tube amp with no power cord...under the chassis there's a tab
with a black and a red wire. The fuse inside amp is attached to black
wire.

So I attached a 3 prong power cord with black, white, green wires. I
attached black to black, white to red, and green to the chassis.

I plug it in and my circuit breaker trips! But, If I unhook the green wire
from chassis, I can plug it in and it seems to work fine, though I haven't
touched the thing without gloves on.

Did I screw something up? I can leave green wire off but if it's unsafe I
don't want to mess with it.

Thanks for any help