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Fanmanj 
Bronze Level
Joined: 08 May 2011
Location: Thibodaux,la
Points: 19
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 Topic: Diode instead of cutout on Allis B?
Posted: 10 May 2011 at 1:36pm |
OK... my next question. I've checked out the generator on this Allis B. Changed the brushes, cleaned the commutator, and sure enough, she spins when 6V is applied. I installed it, fired up the tractor, and it still isnt charging! now there is this diode mounted to the generator, i'm guessing as some sort of modern repacement for the cutout? other than the diode, the electrical system looks in order. I can put the Charge/light switch anywhere, and the ammeter doesnt move... Help before I rip the 6V stuff off and install an alternator (which I dont wanna do). I think I polarized the genny right. touched the armature terminal (the one with the diode)  to the positive on the battery.
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Coke-in-MN
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Joined: 12 Sep 2009
Location: Afton MN
Points: 41785
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Posted: 10 May 2011 at 2:12pm |
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Is your diode good ? check with meeter to be sure it is passing voltage in one direction or not open . If you ground the field you should have full output from gen.
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Faith isn't a jump in the dark. It is a walk in the light. Faith is not guessing; it is knowing something.
"Challenges are what make life interesting; overcoming them is what makes life meaningful."
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Fanmanj
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Joined: 08 May 2011
Location: Thibodaux,la
Points: 19
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Posted: 10 May 2011 at 2:42pm |
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that's the strange thing... the field terminal has been grounded to the generator body with a short wire and eyelet (visible in pic), and the armature terminal is the one that goes through the diode.
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cmsmoke
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Joined: 19 Feb 2011
Location: Johnstown, Pa
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Posted: 10 May 2011 at 3:05pm |
Aren't "B" models positive ground? If the feild terminal is grounded (full feilding the generator) it should be making full output. The red wire goes back to the ampeter then to the battery negative. The ampeter could be open as well. If it doesen't flow through, the machine won't charge. The diode only lets the current flow out of the gen.. If it wasn't there, the gen would spin just like when you powered it up.
It has been a while for me to revisit a positive ground charging circut, but I will check the "C" manual tonight. Someone correct me, if I'm wrong.
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Fanmanj
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Location: Thibodaux,la
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Posted: 10 May 2011 at 3:30pm |
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Yep it's set up as positive ground. I'll have to check the ammeter.
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Tedin NE-OH
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Joined: 30 Mar 2011
Location: OH
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Posted: 10 May 2011 at 3:36pm |
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If you suspect the diode just jumper it to see if you get charging then. The purpose of the diode is to prevent the discharging of the battery back through the genny when the engine is NOT running.
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cmsmoke
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Location: Johnstown, Pa
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Posted: 10 May 2011 at 4:10pm |
Also depending on if your wiring has been reworked, the headlight switch origionally controls the rate of charge. See if it may have been bypassed and/or loose connections.
This may help.
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CTuckerNWIL
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Joined: 11 Sep 2009
Location: NW Illinois
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Posted: 10 May 2011 at 4:14pm |
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And if the light switch isn't grounded well, it won't ground the field even with good wiring.
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Brian Jasper co. Ia
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Joined: 11 Sep 2009
Location: Prairie City Ia
Points: 10508
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Posted: 10 May 2011 at 6:40pm |
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The best test for that diode would be with a light bulb. A digital meter may not be able to "turn on" the diode. It should conduct power one way and not the other. The original generator should be a 3 brush style. The 3rd brush is used to set the max charge rate. You can remove the belt, disconnect the field terminal, and jump the diode with a wire. If the generator spins fast and slows down when you ground the field, you know the wiring and generator are good.
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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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