If he has ac voltage at the regulator, and the diodes are open.. then he could just replace the rectifier (s) just depends on how handy he wants to get.
"Norm, it seems, but I am not sure, that this unit uses external full wave rectifiers built into the regulator. He has 30 volts AC out of alt but no DC at bat. If AC is making it to regulator but no DC is coming out then it looks like the rectifiers in reg are open circuited. It's time to replace regulator which I think he is going to do."
I've seen both the pulse width modulated fields like you mention, and a simple 100% on time variable field density setup as well.
"Soundguy, regulators, as far as I know, modulate field current by turning on and off current flow through the field windings at a rapid frequency (duty cycle). Field on time will be high with heavy electrical loads and low with light loads. "
Two stage mechanical voltage regulators, a most comon type, also use shunt circuits when in their second stage. Depending whether they are of the "A" or "B" types, these units will shunt either the B+ or the gnd side of the field circuit to shut off field current flow when peak (limit) alt voltage is hit.
Shunting the field is a much different case than shunting excess charging current. I've seen many setups that shunt the field to produce a definate 'off state'. In some transistor circuitry negative bias is often used for 'off state' situations ( ( base and/or gate ).
"On controlling alt output by using an "end stage regulator"."
"These units work by taking excess current and voltage (watts) and converting the excess to heat. They are not very efficient since there is no point in using fuel to make power and then throw it away. "
My point. why make it to waste it. But keep in mind that there are also end stage regulators that do not shunt excess supply voltage in order to regulate output voltage. For a simplified idea, pull up the specs on a 7812 from the radio shack web page. Though we are talking about a tip style package with a 500ma to 1amp capacity, the concept is the same.. just a smaller or larger scal application.
"My apologies to the group for all of this technical garbage.
This charging problem, while interesting, has spun out of control."
I wouldn't categorize it as out of controll. And as for techo-info. Seems the more the better. I see no need to appologize either. The topic we are discussing is 'charging systems', and our discussions back and forth, are without a doubt, on topic.
In deference though, I believe that we may be doing a bit more theoreticle work on a tractor charging system than the original engineers who designed it. But heck... it is fun, and that is why we own these tractors anyway... for the hands on experience.
Soundguy
