Today I received and interesting email about an ST head that would not self excite.
From: Rick S.
Subject: ST Head
I bought your Utterpower Cd a few years ago and had trouble free running a Lister with the ST head, But now I have a problem with the head not self exciting.
If I use the battery method to reflash all is ok and generator works perfectly no problems at all, but if I stop and restart the generator It produces no current until its reflashed again.
Whatever is happening its not holding any residual magnetism at all.
Have you ever had this problem before?
All ohm readings at the beginning are still the same today so I know all is ok apart from the problem I mentioned.
Look forward to your reply
Great topic! As you know, the ST head works exactly like so many hardware store generators, the source of field power comes from the harmonic winding in the stator, and is then routed to the rectifier to be rectified to DC and then onto the field via the brushes.
For the sake of others who follow, the generator normally holds some residual magnetism, and will start on it’s own. when it doesn’t there may be a combination of troubles, and there’s a reason to check things out..
I never trust the factory wiring, I check every brush lead, and every connection, I don;t trust the chinese rectifier, and I replace them with a western 30 amp unit with a 1000 volt PIV rating.. way overkill, but it’s what I do.
the battery flash may be temporarily healing a bad connection.. check them all, and do put as much load on the generator as it will carry and leave it there for a bit.. check the field voltage against the name plate and report back.. please..
This is a simple system, and it will be a simple problem.. when you bring the generator upto speed, take an AC reading at the AC side of the rectifier..