I have an old Crown D-60 power amp that was working fine until a couple of days ago. I turned it on and it blew the fuse (one of those small 2 amp glass fuses). I went out and bought an indentical replacement but it also blew as soon as I turned the amp on. The amp has been mounted in a rack in my studio for almost 5 years and hasn't been moved during that time. What would cause this? I'm assuming that some component somewhere has failed due to age?