I'm going to throw another potential out there, since the fuse was blown - electric short due to heat and increased connectivity. One thing I have learned is that these old bikes are bullet proof but like to run minty. Electrical connections tend to get dirty over time, so going through all the connections with a cleaner such as Deoxit will make a difference.
Although, I'm thinking one of your plastic multi pin connectors is bad in a location where heat builds up. On my bike a 6 pin connector under the tank created a problem.
I suggest using the FSM to locate and go through all the electrical connections, test the relays and rectifier, battery voltage, wire connectivity, replace the spark plug caps if they are original.
Another favorite would be POINTS and in your cause maybe condensers. These bad boys are the root of all evils on these Old Bastards.
Keep trying by testing and ruling out good working parts. Slow and steady and avoid breaking stuff.
Is there enough gas in the tank? I prefer to run with plenty verses turning the petcock to reserve - always run with the petcock on "On". Does your petcock have just a single fuel line or does it also have a second vacuum line?
... just my 79 cents - and Welcome!