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The bulk of the old tractors i look at that have bad battery trays / boil overs are those with simple cutout relays, and either manual adjust 3rd brush type units.. or lamp switch /tickle resistors that set a charge rate independent of load. I personally feel that the bulk of VR problems are caused by user error.. I.E. hoking up battery wrong polarity and starting tractor before polerizing, or polerizing incorrectly. To further that list.. I do believe a cheap VR is a waste of time. Unless the VR costs about 40$.. I'd call that cheap. I get my VR's from the mom-n-pop alt/gen/starter repair shop in town. Another issue is plain bad batteries. people need to realize that batteries go bad long before they completely die. Most people will run a battery till it will no longer crank or charge up.. what they don't realize is that while that battery is aging past it's useable life.. cells may degrade, lowering output voltage, and charge current consumption can go up.. this leads to excessive charging.. I almost never see a battery less than 5 years old when i go see a farm tractor.. I see 10 and12 year old batteries... and I fully expect those old suckers to draw excessively.. have less cca, leak and boil over.. etc. Heck.. as cheap as i am.. I can afford to buy a 29$ battery every 3-5 years... I even keep a spare 6v battery for when i go to shows, cause everyone knows most ignition and charging problems always crop up at shows! Lots of our construction equipment at the GC I work for is 60's vintage.. .. some older.. most of it is 790's 80's and 90's. We have buffalo and ingram rollers from the 50's and 60's.. all are on 6v p-grnd genny systems. wE HAVE A COUPLE MORE MILITARY SURPLUS ROLLERS WITH GAS ENGINES ON 12V N-GRND GEN sysstems (oops.. capslock..).. We have a continental power unit on an liquid asphalt distribuitor tank with a 6v p-grnd genny. Add to that a small handfull of industrial truck on old alternators with external regulators. Our mechanic is not electrically inclined. Any chargeing system problems always get refered to me.. new alternator instalss.. etc. I can tell you we have the bulk of the problem with the new 50$ auto store reman alternators and bad wireing. The old gennies are just sooooo fault tolerant. I've seen smoked units come in.. where an operator pinched a wire and burnt up everything from the armature wire to the key switch.. etc.. you re-wire.. re-polerize and go.. on the alternators that come in like that... 90% of the time the alt is toast.. 0 fault tolerance. Mechanic was hooking up an alt the other day started the truck up to test it.. dropped his wrench.. and wouldn't you know it.. hit output stud and fram of alternator.. made a shower of sparks, and it caught on fire!.. nearly ruined a good snap on wrench too. Those are just my personal experiences... course.. I'm pretty good with electronics.. so most of my equipment is in good condition.. electrically speaking. On the flip side.. if you don't like a mechanical VR... build a small solid state one. A piece of breadboard the size of a 50 cent piece and a small handfull of radio shack components will get you a neat solid state fixed, adjustable fixed, or straight adjustable control circuit suitable for powering the field of a 6v, 8v or 12v A or B type field circuit, negative or positive ground. Positive ground setup requires a bit of circuit trickery, and possibly case isolation.. but that's no biggy. Anything from pwm, to a couple different comparitor circuits, to plain 3rd brush type rheostat control.. even variable biased transistor field control.. etc... No polerizing of the vr needed.. etc.
Also.. if you want to simple make an output control circuit. like the kits for replacing the cutout on a 3rd brush.. a series pas regulator is ultra easy to whip up.. way way easier than the variable field control... using big silicon.. like T0-3 series stuff, large current isn't a problem.
Soundguy
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