I can't seem to find the reason my Fisher amplifier keeps blowing the 7 amp slo-blo fuse. It plays fine on my test bench but when I connect it up the my other equipment. The fuse will blow. Sometimes it plays for days without blowing the fuse. I checked my speakers and speaker connections and no problem. I checked the fisher to see if one side of the line was connected to the chassis but it's okay. Yesterday the fuse blew again and I replaced it. The fuse again blew so I reversed the AC plug (not polarized) and the fuse did not blow. My next step is to see if my pre-amp has one side of the AC line connected to ground. This may or may not be associated with the fuse blowing but after playing a tape on my Pioneer RT-909, the tape will slow down after 15 minutes or so. Any ideas? I've attached the schematic of the Fisher amp.
Thank you for your help.