I Want a cheap and easy "Confidence Builder" amp kit.

[g1]

I measured Voltage between EL84's pins 7 & 3 (plate & cathode) at 245.7 VDC. The OT primary at 226 ohms, and Voltage across OT primary at 5.64 VDC. So, using a calculator Plate current is 5.64/226 = 25 mA and Plate dissipation is 245.7 VDC * 25 mA = 6.14 watts. If I'm correct, the EL84 is idling at ~50% maximum, right? If so, can I fiddle with the Cathode resistor to increase the plate dissipation?

A simpler way to find the current is to just take the voltage across the cathode resistor and divide by the resistance. This also includes screen current but it changes the reading very little.
The schematic calls for about 28mA current. (5.5V divided by 200 ohms). So you are right in line with the recommended bias. You can play around with it if you want, but if there is no big benefit (tonally) to your ears, the lower current will increase the tube life. You may find a compromise somewhere between the factory spec. and the maximum.

[Chuck H]

What Helmholtz and g1 said^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Yes you can lower the cathode resistor value for more current. 100% rated tube dissipation at idle for class A in your case is fine. As mentioned, class A means that the one tube is biased so that signal swings from the center of saturation and cutoff. So you can only expect half peak voltage at either end. Since your voltage is a little on the low side I think you shouldn't expect more than about five watts. A bit less actually because tubes are never operated in perfect, on paper circumstances and there are losses in the circuit elsewhere.

[gui_tarzan]

I think for modern Fender amps, fuse on live side is common, but power switches usually open both hot and neutral.

There would be no reason to put a fuse to neutral (which ties to ground at the panel anyway) and keep the hot line hot. I see it in a lot of schematics and always wonder why. If the switch gets bumped or left on and you touch the hot line in the chassis, you're going to ground it and get shocked even if the fuse on the neutral blows. I always put the fuse and switch in that order before tying into the power transformer. Then if the fuse blows you have nothing "hot" inside the chassis aside from that one side of the fuse holder. Unless of course someone wires the outlet you're plugged into wrong. I found a few of those in our house after we moved in.

[Enzo]

The reason they wire hot to switch and neutral to fuse is convenience. In th days of two wire cords, you could not count on which wire was which anyway. If we wire it like we should, we splice the neutral to the transformer primary wire, then series wire the fuse and power switch to the other lead. But that requires a wire splice or mounting a terminal strip. In the old Fender chassis, they could run the two mains wires in, terminate one at the fuse holder and the other at the switch. No extra parts or work needed.

Not defending, just explaining.