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ferdd

Rectifier circuit for 727

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ferdd
Does anyone have a schematic for a dual circuit system? The rectifier I need #390892 is nla. Any ideas on how to get this to charge the battery?. I only need the dc side to work. Thanks Fred

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ferdd
quote:
Originally posted by dutch: Didn't the 727 use a starter/generator as OEM? What are you trying to rectify? Has the engine been replaced? If so, what engine is it?
Replaced with a 190707 type 0793. From a Case 108

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ferdd
quote:
Originally posted by KSever: I don't have the picture of the wiring for the rectifier but on my 717 I found this to be helpful.
I have the same picture. What I'm looking for is a schematic that shows what's in the rectifier. Or a substitute. Fred

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Dutch
Dont' know what's inside, but if your regulator/rectifier looks like this, the center wire is + DC out (to battery, and the other two are AC from the alternator. Ask your dealer if a B&S #435195 will work.

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Spyder
Don't know exactly what you are referring to as your rectifier. Most of the circuit diagrams shown do not contain a rectifier that I can identify. Electrical rectifiers are semiconductor devices similar to common transistors. The rectifiers insides consists of layers of certain metals and additives whose bonds form intricate electrical junctions. The exact way it works gets into Nuclear Physics and Mathematics so I don't think I can explain that in a short message here. The rectifier can conduct current in only one direction. And it can stand voltages in the reverse direction of thousands of volts. The transistor can conduct current with a control signal so it can be regulated electronically. Electrical rectifiers are used in Alternators to turn the varying voltage (alternating current or AC) into a constant voltage which is Direct Current or DC for short. This is the voltage which charges the battery, powers accessories and lights, and runs the voltage regulator. The voltage regulator is not a rectifier as such. Its job is to regulate the DC voltage on the battery so it does not get overcharged. However, the devices used in the electrical diagrams in the thread above are all DC components. There is no alternating current so no voltage rectification should be necessary. If your new engine uses Alternators instead of Motor/Generators, then the rectifiers are inside the Alternator. Sometimes, replacement electrical rectifiers can be purchased at Radio Shack to fix Alternators. The part number they would have is 1N4004. You'll need a little electrical expertise and a good soldering iron to do this. The price of the 1N4004 is less than a buck. I'll check this thread later to see if we are on the same note. Hope this helps. later....DaveG

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KSever
Dave and Fred, My 717 had a rectifier on it and it was hooked up for some reason to the alternator. BUT it was not charging the battery. This tractor had originally had a starter/generator on it when it was purchased from the factory, but had a newer engine installed in it when I bought it that had a alternator on it and not a starter/generator. My guess is, it was hooked up with the rectifier when in original state. And the previous owner thought he had to rehook that way also. SO, when I unhooked the this rectifier and ran the wires staight off the stator (which has a diode in the line) as described in the pictures above my battery started charging at +4 amps. Just my experience and 1 cent worth. Kris

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Dutch
Don’t forget, magneto ignition engines do not need an alternator (stator) to run. For example: Rope start push mowers. Some magneto ignition engines have an alternator (stator) only to power AC work lights. For example: Rope start snow throwers. Other magneto ignition engines have an alternator (stator) to recharge a battery. For example: Electric start tractors. Engines that have an alternator to recharge a battery use diodes to convert (rectify) the alternator AC current to DC current. The diode rectifier may be internal (wired into the stator), or the rectifier may be external (in a separate box). Recharging a battery also usually requires a regulator. The regulator is in a separate external box. Sometimes the regulator and rectifier are combined in the same external box. It doesn’t require much know how when replacing defective OEM parts. However, when swapping engines or making other modifications, it’s best to have an understanding of how systems work, and to use meters and other test equipment for selecting suitable components and rewiring.

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ferdd
quote:
Originally posted by Spyder: Don't know exactly what you are referring to as your rectifier. Most of the circuit diagrams shown do not contain a rectifier that I can identify. Electrical rectifiers are semiconductor devices similar to common transistors. The rectifiers insides consists of layers of certain metals and additives whose bonds form intricate electrical junctions. The exact way it works gets into Nuclear Physics and Mathematics so I don't think I can explain that in a short message here. The rectifier can conduct current in only one direction. And it can stand voltages in the reverse direction of thousands of volts. The transistor can conduct current with a control signal so it can be regulated electronically. Electrical rectifiers are used in Alternators to turn the varying voltage (alternating current or AC) into a constant voltage which is Direct Current or DC for short. This is the voltage which charges the battery, powers accessories and lights, and runs the voltage regulator. The voltage regulator is not a rectifier as such. Its job is to regulate the DC voltage on the battery so it does not get overcharged. However, the devices used in the electrical diagrams in the thread above are all DC components. There is no alternating current so no voltage rectification should be necessary. If your new engine uses Alternators instead of Motor/Generators, then the rectifiers are inside the Alternator. Sometimes, replacement electrical rectifiers can be purchased at Radio Shack to fix Alternators. The part number they would have is 1N4004. You'll need a little electrical expertise and a good soldering iron to do this. The price of the 1N4004 is less than a buck. I'll check this thread later to see if we are on the same note. Hope this helps. later....DaveG
Hello, This engine has an aluminum box under the blower housing with 2 wires coming from the alternator and a red wire that goes to a fuse holder on the other side by the starter. My understanding form the b&s book is that there is ac on both black leads into the box and comes out on the red lead as dc. I don't know if the box is a rectifier and regulator but 12 -14 volts dc is supposed to be on the red lead at the fuse holder. There is also a plug with ac under the fuse holder for the lights. If the 2 black wires at the box are connected to one side of the diode and the red to the other the problem is solved. I don't think it's quite as easy as that. I'll try the radio shack part to see if it works Thanks Fred

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PatRarick
I finally understand what you are talking about (takes me a while sometimes). You do not need a rectifier. The connection with the "fuse holder" should have a diode inside. It is not removable without cutting the wire. If you can pull it out of the holder, (carefully, and you may have to unscrew the box from the engine to get enough wire) you should see a cylindrical unit about 3/16" in diameter, and 3/8" long, with a heavy, solid wire which is soldered to the alternator wire. That is the diode. It converts the AC current to DC for charging the battery. If you have that diode, you only need to solder a wire connection or your charging wire, to the "head" on the open end of the diode. If that diode is missing, you need Briggs #393814 diode assembly (about $8.50), and alternator harness #393422 (about $6.25) Pat

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ferdd
quote:
Originally posted by PatRarick: I finally understand what you are talking about (takes me a while sometimes). You do not need a rectifier. The connection with the "fuse holder" should have a diode inside. It is not removable without cutting the wire. If you can pull it out of the holder, (carefully, and you may have to unscrew the box from the engine to get enough wire) you should see a cylindrical unit about 3/16" in diameter, and 3/8" long, with a heavy, solid wire which is soldered to the alternator wire. That is the diode. It converts the AC current to DC for charging the battery. If you have that diode, you only need to solder a wire connection or your charging wire, to the "head" on the open end of the diode. If that diode is missing, you need Briggs #393814 diode assembly (about $8.50), and alternator harness #393422 (about $6.25) Pat
Hello, The system I have does not have a diode in the fuse holder, it has a 7 1/2 amp fuse in it. The diode is in the rectifier on the other side part #390892. The one with the diode in the fuse holder is a 1 wire system DC only. I got this from the b&s repair book. I'm going to check the 2 wires coming out of the stator with a meter for AC, maybe I can use one of those with a diode to charge the battery. The system you describe has 2 wires going right to the connector, mine has them coming out the other side by the carb and going into the rectifier and then the red wire goes back across the stator and comes out to the fuse holder. Below the fuse holder is a push on connector for the lights. I can read AC there but it's only about 6-8 volts AC. Something in the rectifier connects the two black windings together then puts it through a diode and it comes out to the fuse holder as DC. The rectifier must have something to do with the AC side also as 6-8 volts AC is not enough to make the lights work. I think the only way I can get this to work is to change the stator to part #391529 ( the system you described). Thanks Fred

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HubbardRA
If the alternator is working, you can buy a bridge rectifier at Radio Shack or any electronics store, hook the two AC wires to it and then take the DC outputs to a voltage regulator from a starter-generator system. I have done this before. Rod H.

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