brushless alternator?
 

Don't get all defensive now. Oil filled caps have been around since
the, well, before I was born and they just don't die - and I've tried.
Got a few in my unreg choke input filter HV supply from the 40's still
going strong.

Some AC motor run caps look like oil filled types bur are dry and a
lot less permanent, and lighter weight - like one sees in microwave
ovens. I'm guessing you might have one of those. Crimped drawn
metal, aluminum case, with a plastic insulator - no elastomer seal, no
porcelain turret connectors and a quick connect, push on connector.
Looks similar to the old oil dielectric caps, but a lot more capacity
and a lot less rugged.

Cap could be all the problem . . . but a 50 uf cap would suggest it is
just there for sine wave smoothing and not a necessary generator part
- but I don't know what your load looks like to the gen either.
Try changing the cap with a new one - that may be all that's wrong.



Sorry, I just get a bit irked by all the knee jerk reactions implying that
I'm some sort of idiot, I've been around here for a long time and know how
to properly test components.

It may well be a dry cap, I just assumed it was oil filled because it's
metal, has a soldered closed hole in the end, and says "No PCBs" on it. I
also noticed tonight that it says "Protected" on the end which I assume
means it's internally fused. I'll cut it open later to find out what's
inside. At any rate I ordered a new cap, it was only $1.75 from a surplus
outfit and I needed some other stuff anyway. If installing that doesn't fix
the problem I'll dig deeper.