The harness is for the most part color coded so there is a lot that I can piece together but its still a lot of effort. The diagram would at least verify the connections, which I would like as I've still not found something like an isolation or step down transformer. I am starting to wonder if this thing is ACTUALLY 120v in both input AND signalling. Terrifying. Not even 24v AC?
Also yes the two fuses are ye ol screw-in type. One for either side of the AC input and rated for 15 amps. I could keep them in there but I've been holding onto a few of the mini breakers for years now and this would be a great time to use them.