Does anyone know how to troubleshoot/fix one of these? Thanks in advance..
I have repaired a couple of these but I am a bit to far away to help you direct. In both cases it was the cutout diode that failed almost certainly caused by misuse or bad set up of the generator.
That's not a cutout, there's only a spool with contact points or a single diod inside a cutout. This is some kind of voltage regulator - if it's a Fun Projects regulator from John Regan, you shouldn't have removed the cover - it'll be more expensive to have it fixed now. (You can determine whether it's a regulator or cutout from looking at the underside - there have been photos posted at the forum)
Here's a 2014 post from John regarding his policy towards repairing regulators that were killed in action (most often by being connected to the wrong polarity, I think..)
"We offer a flat rate repair for repairable regulators. This flat rate applies only to regulators that have not been tampered with (cover removed is tampering). We will repair regulators that can be repaired even if tampered with but not for the current flat rate of $20. We ask that you send the regulator to us with cover still installed, along with $20 (personal check is OK) to Fun Projects, Inc. If the regulator tests good then you get all your money back except return shipping which at this time is $4. If the unit is faulty but repairable then you get it back repaired but we keep the whole $20. If you want an unrepairable unit back then we keep only $4 for return shipping otherwise a totally unrepairable unit is not repaired and we return the whole $20. Most of the regulators sent to us test good."
It is a fun projects regulator.