Alternator, Pt.2

[elippse]

As I wrote before, my alternator stopped working so I pulled it out, dis-assembled it, took it to an auto electric, and they fixed me up with new brushes and bearings to the tune of $19.12 with tax. On my first trial before I put the cowl back on, it seemed to be charging, but not at very high current. OK, job done! Put the cowling on and taxied to the end of the runway and the LO BAT warning came on and then it started showing discharge. I removed my regulator and took it home for bench testing and everything was OK there. Back to the hangar and set up a test fixture driving the alternator with my drill press and connecting the regulator, alternator, and battery together and checking the field and output with a 'scope; it was taking a lot of field current for very little output current. Did the same set-up with a different alternator with very different and better results. Back to the auto electric with the parts and the owner could see where one of the diodes had a black area around it. New diode plate for $50 + taxes and now its working like a charm. Were the several days of trouble shooting vs buying a rebuilt for $200 worth it? You bet! I've seen some of these rebuilts where they wiped it off with solvent and sprayed it with black paint. This way I have new brushes, bearings, and diodes, and it'll be around a lot longer than me!