more on cub genny delima

Here is some background info.

Some time ago ( last year at the end of mowing season) one of my cows got in the barn and ran her horns all over my 1966 IH cub. Pulled the ignition and genny/regulator wires. I put the ignition back together, and frankly.. just left the genny disconnected, as I could mow all day, and never know the difference. i use solar 'maintainers' on the tractors.. and over the course of a week, the battery was topped back off.. So I never had to jump the unit.. so that kept me 'lazy' enough not to tear into it. Besides all the other farm stuff that needed to come first. I decided to get into it yesterday and today.

Ok.. unit is a 1966 IH cub. According to SN it is one of the first units that was 12v. The I&T manual is a little stingy with exact regulator and genny info.. though there were -MANY- 6v generators used, and a couple 12v gennies. same with regulators too.

At this point.. I'm going to guess that this genny has either been rebuilt, or is just plain not oem. It's armature and field terminals are reversed from what the schematics show on all the other gennies. It is a delco unit, and does fit the oem mounts Here's where it gets funny. The 12v units, in the book, are negative ground. After fiddling with it, and doing a bunch of testing, nd work.. this unit simply will no longer charge as negative ground. I even pulled the regulator completely off, and full fielded the genny and measured the armature, after polarizing it first. No charge.. nothing.

i swapped the battery to positive ground.. polarized the genny.. and it charges perfect. I'm using a big diode and a 3 ohm 10w power resistor as my 'regulator' right now. I'm going to test the genny tomorrow to see if it will run positive ground. The regulator is obviously a 'replacement'.. new vintage.. does say 12v on the bottom of it. Deffinately is an A-circuit genny, due to the placement of the external resistor from the field tab, wired to the mounting plate.. providing some field resistance even when the contacts are open.

The genny responds as an A circuit as well.. ( oem was a- circuit too.. Hmm )

In all other respects, this genny checks out. Brushes look good.. good commie.. no shorts I could find.. etc. field insulation intact.. correct field amperage range of draw according to the fo manual, and even correct voltage and current output range on the armature. ( up to 14v and 25a.. and yep.. it will pump that out.. 14v max.. and 20+ amps when full fielded. )

Unit motors and does have a current draw at the armature, with the armature and battery jumpered ( as it should).

I looked like a mad scientist out there today. I had about 50 jumper wires and 3 VOM's set up and going. measuring field draw, armature output and battery voltage, the tractors ammeter was also in circuit showing 'net' charge.. etc. All looked 'good' and what I expected. Output was a nice 'dirty' dc 'waveform' according to my o-scope.. exactly as I expected it to be.. and have observed from my other gennies..

I have noticed a few other peculiar things about this tractor. It was sold as a 51 cub.. but clearly is a 65+ due to the sheet metal, and other features, like seat frame mounts, hydro pump, etc. The wire diagram for all the new units is straight 'regulator' run for the genny charge, while some older units did also use a lamp switch resistor wired to the genny, and no connection to the field tab.. according to some of the 6v diagrams I could find... This tractor does have a lamp switch equiped with that resistor.. however it was not wired to the field. I wonder if the lamp switch was a 'one size fits all' model, and was just universally used?

In any case. I'm going to dink with it omorrow. but really need to button it up, as I can't spare much more time on it. I'll test the vr to see if the cutout is still working and if the voltage contacts work.. if so, I'll install it and polerize it as positive ground and just run it that way,as the genny is fine with that... I fhte regulator is cooked.. I think I'll leave my diode/power resistor setup, possibly with a toggle switch option to switch in some more resistance so i can have a low/high charge setting.. perhaps even use the built in resistor in the lamp switch??

I'm still puzzled why it will not run negative ground. the armature and field being in different locations from the book lead me to believe this is not the stock genny.. but one the owner found that would fit the brackets...

You guys know of anything that would lock a genny into one polarity?

Comments and ideas welcome.

soundguy

The diagram in the Parts Catalog isn't clear on 12v wiring, but it gives the appearance that the A and F terminals on the generator may be swapped position wise from how they were on the 6 volt generators. Just go with the markings on the generator frame and don't worry about it too much. If the generator still has the Delco data tag, what model number is on it?

There is no reason a generator cares which way it is grounded. Whichever way it is polarized it will charge. If you reverse it and don't swap the ammeter connections, one way or the other will show discharge when it is really charging.

If you have a solid state regulator it will only work one way. Your diode and transister regulator will only work one way. The original units were A-circuit.

The serial number should tell you the year of the tractor but the front housing could have been changed, including the serial number plate. A 12-volt tractor (serial 224401 and up) would have the starter switch in the dash or be solenoid actuated. Hydraulic pump won't tell you much. The Early light switches that controled generator output were not installed after 1950. Those switches had 2 resistors, later switches had 1 to dim the headlights.

I've identified the armature and field posts.

The ammeter connections weren't at issue. It simply would not charge when hooke dup as negative ground. I pulled the regulator out of the circuit. Used a resistor in line with the field, to ground.. low enough resistance to allow for a 'good' charge. I used the diode merely as a 'cutout' to prevent current from backflowing through the armature when not spinning.

I didn't bother trying to build a transistorized regulator for it.. though I have on other tractors.

Anyway.. when hooked up , and polarized.. it simply won't charge as negative ground.

If you swap the battery, change the orientation of the diode, and repolarize as positive ground, it charges good. I tested using a 3 ohm resistor between field and ground, and that produced a range of voltagf from 13-14v and 8-12 amps, from idle to high idle.

Simply does nothing when setup as negative ground. I'm at a loss for that reason?!?

Tag is delco, but is illegible.

I agree front pedistal could have been swapped.. but everything else I've seen so far indicates that this is a post 65 tractor.

Starter button is on the dash. After double checking.. this has the lamp switch with 1 dimmer resistor.. so that info matches up.

Appears to be the proper vr.. it is listed 12v and has the L terminal for ignition.. etc.

I messed with it this am, and the regulator seems to polarize correctly positive or negative ground, in relation to the cutout working. I tested it off tractor using 2 12v batteries and a charger. i hooked the reg up to one battery.. polarized, and used the other battery with charger on it as the 'genny', and the cutout corectly closes when voltage on the gen tab excedes volage on the batt tab, and correctly closes when votlage on the gen tab drops below votlage on the bat tab.

Regulator is an A circuit regulator as evidenced by the bias resistor to ground from the field tab.

I'm going to go mess with it some more.

Unless I want to spend the money for a new gen and reg.. I guess I'm going to have to live with it as a positive ground system.... unless I miraculessly find somehting out here soon.

Soundguy