"Do you think it would be safe to conclude that the proper sized ballast can be determined with an ammeter, instead of measuring it's resistance, 4 amps when it's powered up? "
I don't have a problem with the use of a good analog ammeter myself. An "ideal" (none such made however) has zero resistance so as to NOT affect the reading. The critical limiting factor (to prevent premature points failure) in a typical old tractor coil ignition is how much current the points can pass and switch so if you get that in the 4 amp range and provided 4 amps is a sufficient coil current I say compute the ballast resistance by that method makes sense. That's where they get the typical 3 ohms vicinity for 12 volt coils and 1.5 for 6 volt coils as that yields the 4 amps of points current. NOTE these are not all exact figures, I've seen stock 12 volt coils from 2.5 to 3.5 ohms.
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Today's Featured Article - Sunday Drives - by Cowboy. Summer was finally upon us here in Northern Maine. We have two types of industry up here, one being "Forestry" (Wood Products) and the other "Farming" (Potatoes). There is no shortage of farm tractors and equipment around here! I have been restoring old Farm Tractors for the past 6 years, and have found it easier and less expensive to hit all the auctions and purchase whole tractors for parts needed. My wife who works at a local school, and only has weekends and summers off, while on t
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