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Discussion Starter #1 (Edited)
I just bought this 102:

http://www.mytractorforum.com/showthread.php?p=704217#post704217

which would crank but not charge. A little fiddling id'd the cutout relay in the regulator. Hooking it to a bench power supply would not pull the relay in up to 20V!! Later, when destructing, I determined that the voltage coil was open. So I went to RadShack, bought a 20A bridge rectifier. A single diode would work, but they had none large enough

Step one:

We have folded up the armature, and cut loose the heavy current winding and pulled it off the core. You can see part of the wire in the back of the picture The cutout, by the way, is the relay with the normally OPEN contacts. The voltage regulator relay has a normally CLOSED contact. DO NOT disturb any of the VR relay or wiring



Step two:

Grind off the rivet holding the relay to the base:



Step three.

Cut loose the wiring and remove the rest of the cutout. Wire and tab on left is gen connection, wire going to bottom right goes to battery. The terminal is I guess the lamp terminal, as the load goes THROUGH that coil in the regulator and up the other way. In any case that's the two former contacts connections



Last, mount and wire the bridge. I connected the AC connections together which will cause two internal diodes to be paralleled, and the AC connections goes to the "gen" terminal. The case had a corner clipped for ID, so I mounted that up against the one rivet for better clearance. The + DC terminal then goes to the wire which feeds the current coil in the regulator relay

It's difficult to see in the pic, but the two corner to corner connections are jumpered to the top left (AC goes to gen) and the + is the front connection closest to the relay




Someone on another forum was concerned about the voltage drop through a diode junction, but the fact is, the regulator simply jacks up the voltage to compensate. The regulator "sense" lead---the voltage coil for the voltage relay--hooks to the Bat terminal, so the diode drop is not important.
 

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N I C E W O R K.... I realy mean that.
I can appreicate the thought and enineering you had to do there.
 

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Parts Robber
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nice job but not sure messing with voltage regulator in inexperienced hands is a good idea. Could turn into a fire hazard real quick !! burning up a wire harness or worst a whole tractor not worth saving $50.00 to me.
 

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Discussion Starter #4
nice job but not sure messing with voltage regulator in inexperienced hands is a good idea. Could turn into a fire hazard real quick !! burning up a wire harness or worst a whole tractor not worth saving $50.00 to me.
First, I'm not "inexperienced" if that's what you were suggesting.

Second, I'm not sure I buy your arguement that just because you spend 50 bucks on a new regulator that somehow makes you "safe." Many things can go wrong in these things, including shorting of the high impendance windings, which in either relay could cause a certain amount of smoke being released.

There doesn't seem to be one single fuse or breaker in this harness that I've been able to discover.

Last, all that needs to happen--and does, often, in older systems, is that the cutout relay contacts can weld shut, and well, there you are--a burned up generator, probably a smoked harness, a dead battery, and maybe more.
 

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roadrunner, Nice work there. What is the purpose of the cut out relay? I need a refresher in voltage regs. Just trying to learn something here. thanks
 

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Discussion Starter #7 (Edited)
roadrunner, Nice work there. What is the purpose of the cut out relay? I need a refresher in voltage regs. Just trying to learn something here. thanks
A "normal" generator has three relays, the voltage regulator, the current regulator, and the cutout.

The regulator regulates system voltage, just like an alternator regulator does.

The current regulator protects the generator, which is not "self limiting." If you have a dead battery for example that would "like" a lot of amperage, you can burn up the generator without a limit. Normally 2 unit regulators use a third brush generator, which can be used to limit current.

The reason a cutout is needed on a generator is that when the thing is turning too slow to provide output, or when stopped, the battery current will flow through the generator--IN FACT--on these cub cadets the generator is used also as a starting motor. I once broke a fan belt on my 57 Chev just as I was pulling into the driveway, and when I shut off the engine, the generator was still spinning---The cutout was still pulled in.

The reason you do NOT need them with an alternator is because they use rectifier diodes which only pass current one direction--the very thing that I'm using here, of course.

I forgot to post just what I used. The device is an encapsulated bridge rectifier, which has 4 diodes inside. You normally feed AC into two, and get DC out the other two. I could have used one large diode if I could've found one locally.

Here's what's inside the device I used:



I jumpered together the two terminals marked AC (in this diagram, "in" and used the upper "out" terminal (+) output, leaving the left two diodes wyed to the bottom "out" (-) effectively unused. The + battery is hooked to the upper output . Battery current can not flow back through the diode


So electrically this is what we end up with:

gen output comes in at left, battery is hooked to right

 

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Parts Robber
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First, I'm not "inexperienced" if that's what you were suggesting.

Second, I'm not sure I buy your arguement that just because you spend 50 bucks on a new regulator that somehow makes you "safe." Many things can go wrong in these things, including shorting of the high impendance windings, which in either relay could cause a certain amount of smoke being released.

There doesn't seem to be one single fuse or breaker in this harness that I've been able to discover.

Last, all that needs to happen--and does, often, in older systems, is that the cutout relay contacts can weld shut, and well, there you are--a burned up generator, probably a smoked harness, a dead battery, and maybe more.
I wasn't trying say you are inexperienced or that there is anything wrong with what you did. It looks and sounds like a great job that will work well.

I was just saying that for someone that doesn't know what they are doing it could be an expensive "fix" I've seen many wiring harnesses burnt up because someone tried to "fix' it not knowing what they are doing. I just had a tractor in here that owner replaced solenoid and managed to put 2 ground wires onto hot side of it. Luckly his battery was almost dead (likely original problem anyway) and it just melted coating of one wire before battery drained completely .
 
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