[rotorwrench]

A diode is like a one way check valve. A cut out was originally an electromechanical device to switch the generator on line after it reaches enough voltage to close the circuit. I know that folks still refer to the diode look alike as a cut out but it's not the same critter. Depending on what type of diode was used makes a big difference. Some are near indestructible and some are crap.

Was the armature tested with a growler for opens or shorts. Armatures and field coils can be affected by heat if there is a crack in a wire or a short. A battery can also be affected by heat.

Make sure your battery connections and ground paths are in good condition and tight. Adjust that 3rd brush to limit your amp output. Over amping will cause more heat and a three brush generator always has output unless a modern voltage regulator is installed so they always create some heat unless regulated. The battery is your voltage benchmark so it has to be in good condition and well connected.