I'm working on a vintage Grommes 503 Receiver and came across these capacitors. I assume they are 250ufd and 15v, but could it be the other way around? I can't find a manual or schematic anywhere. On another note the problem it is having is a hum, and no sound on 1 channel no matter the input. So I'm starting by replacing all Caps. Any other ideas what it might be?