A battery charger puts out pulsating DC since there are no filter capacitors in them. Seeing AC is normal and lower than expected DC reading is normal, too. The more modern units will have filtering since they have other circuits that need pure DC. When it is on a battery, the battery acts as the filter.
Maybe you have had an old tube type radio that hummed? That is bad filter capacitors that allow the DC to pulsate a bit.
Try it on a battery and it will probably be fine.
The fins on the rectifier diodes are there to get rid of heat. A diode is like a check valve in this application. It only lets current flow in one direction. The center tap on the transformer allows both the positive and negative excursion of the AC to be used.
Same-Day Shipping! Most of our stocked parts ship the same day you order (M-F). Expedited shipping available, just call! Most prices for parts and manuals are below our competitors. Compare our super low shipping rates! We have the parts you need to repair your tractor. We are a Company you can trust and have generous return policies! Shop Online Today or call our friendly sales staff toll free (800) 853-2651. [ More Info ]
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.