You have a shorted semiconductor device some where in the unit in the power supply or power amp section, they look just fine when they are worthless, there are techniques for testing these devices...I spent 2 years in school learning some of them...go to this website



http://jacquesricher.com/NEETS/ down load and read modules 1-8 and then read module 16, you may at that time have enough understanding on how to work with semiconductors, remember to use anti-static solder equipment and workstation as these devices are sensitive to static electricity..



every time you fuse your amp you are kicking the crap out of your transformer and eventually it too will be damaged, or take it to the shop.