Last Friday when I took my meager rubbish offering to the transfer station my mmmate had two petrol generators put to one side for me, one persons trash is my treasure.
They are 1500 Watt "Super Works" a 5.5Hp Chonda 4 stroke, one had no recoil starter fitted so I concentrated on the other, drained the carby of stale fuel topped up the tank a little, pulled the start chord and away it went. OK so far so good now to look at the generator as there was no voltage showing on the on board AC volt meter, so off came the generator end cap somewhat quicker than a dirty shirt, well almost as I had to strip a bit away to get at it.
Now those two yellow wires and connector sticking up are relevant to this story later on and at 6 o'clock you can see a screw head against a curved bit of casting, anyway suffice to stay the volts I could get were around 9V AC when they should be 240v, not that I was expecting much different, people don't generally dump good generators.
I could see the rotor diodes but to facilitate checking/replacing them I stripped the stator off, there is one diode and varistor in parallel across each rotor coil. At this stage I meggered the two stator (12V and 240V although I suspect it is just tapped off) and rotor coils, all good, resistance measurements seemed to be in the ball park.
Now it is fair to say when one salvages a treasure like one of these just how much fiddling someone else have done is unknown so right back to basics. I removed the diodes and with the aid of my trusty compass checked and marked which imbedded magnet on the rotor was S and N.
I then applied the battery charger set to 6V to each coil to confirm which way the diodes should be to ensure the pole piece windings complemented the imbedded magnet not opposed it. You can see the imbedded magnet in the above pic. That sorted I fitted new diodes and varistors, and re-assembled enough for a test run, but alas still only about 9V AC bar humbug! It was getting near beer o'clock time so a swift clout with a knocking stick managed to break the rear housing.
Time to go find my honey pot and thunk about it overnight, remember I mentioned those yellow wires, well their relevance came to me while thunking so I guess that is why one takes time to thunk about things. For those of you who have not guessed those yellow wires are for the excitation capacitor, so I scratched about and found a 12uF one fitted it and tested out, around 36V AC, OK I would not have thought it needed a higher value than that but in for a penny in for a pound, more scratching and a 20uF was found and fitted.
So having succeeded electrically I applied some Arildite to the broken bits, it is a steady bearing so hopefully it will stay together.
The second unit appears to be newer (less rust and perishing on the rubber mounts) but I can clearly see that the rotor diodes have been overheated.
I will leave checking that unit out till a later date, it's not that I needed any more generators just hate to see waste and someone up here will need a loaner one day, the whole area has no mains power. I was given another unit that just stopped working while running an electric water heater ( my mind boggles) it is another China special 1000W 900 continuous.
That was an easy fix, the rubber fuel line tank to valve had perished and drained the fuel. While none of the above is all that spectacular I thought it may be of interest to show the imbedded magnets and rotor diodes, they were discussed in another recent story by greenkarson but limited pics. Oh and that screw at 6 'o'clock that I mentioned, well the capacitor mount of course.
Allan
