Power fuses are usually slow blow. 2A sounds reasonalble but 3A would not be unusual. 2A is 240 watts. Your amp will pull more current warming up and may actually pull more than 2A for a slort time, thus the slo blow.
I would try a 3A slo blow but first I would replace all tubes. the cause of fuse blows in tube amps is almost always a bad tube. The first suspect was the rectifier because you saw an anomaly there, but it could have been challenged because of a short in one of the tubes it powers. I always have spare tubes, maybe not a spare set of my premium high quality tubes but a spare set of cheap but known good tubes.
Sizing a fuse by the OEM is not generally the precision engineering that you would think. the signal path is carefully constructed with components chosen carefully to achieve the desired result. but the fuse sizing is often a bit of kentucky windage as the designer balances protection of the component with reliable power to the component. some OEMs will put more margin between operating current and fuse current than others.
Even if you try a 3A fuse and it works, I’d try to figure out what changed and fix it. that is harder with autobias. If, on the other hand, you have a short in a tube or similar fault, the 3A will blow just as fast as the 2A.
I like manual bias, partly because you can look at the tube current for each tube.
good luck
Jerry
