I have a Harmony 535 guitar amp that instantly blows the fuse with all the tubes pulled and the amp still in stand by.
There is no sparking or arcing and no popping sound. I need to know how to test the filters and both transformers please. I do have a wiring schematic for this amp.
I have 35 years of experience fixing Major Appliances, I use a Digital Multimeter and I am well qualified on safely tests on live circuits. I have made a dim-bulb test so I can test with out blowing the fuse