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JUSS10

H60 rectifier

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JUSS10

so electrical stuff i usually dont have a problem with, i work with electronics but this little rectifier setup on my 654 is throwing me for a loop. when i look at it, it makes no sense to me, it seems like half of a rectifier being it only has the two diodes thats direct current to the positive lead and the two diodes that usually go to the negative aren't there. I thought i was having a charging issue so i checked my AC voltage and at running RPM it was upwards of 24+ volts AC but after the diodes i would maybe see 6 volts.... I'm kind of at a loss with this deal. can anyone tell whats going on? is one of the diodes bad?

my next question is, is there any reason i can't build a rectifier/regulator with an 8 amp rectifier followed by a pair of LM317 regulators set to 13.5 volts so i get a 3 amp output?

Thanks!

Justin

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MikesRJ

so electrical stuff i usually don't have a problem with, i work with electronics but this little rectifier setup on my 654 is throwing me for a loop. when i look at it, it makes no sense to me, it seems like half of a rectifier being it only has the two diodes that's direct current to the positive lead and the two diodes that usually go to the negative aren't there. I thought i was having a charging issue so i checked my AC voltage and at running RPM it was upwards of 24+ volts AC but after the diodes i would maybe see 6 volts.... I'm kind of at a loss with this deal. can anyone tell whats going on? is one of the diodes bad?

my next question is, is there any reason i can't build a rectifier/regulator with an 8 amp rectifier followed by a pair of LM317 regulators set to 13.5 volts so i get a 3 amp output?

Thanks!

Justin

You are reading AC when after the diodes you are actually looking at pulsed DC. The two diode setup is a half wave rectifier, and is only passing the positive portion of the wave, instead of a full wave rectifiers action of passing both the positive and negative AC swings and individual overlapping pulses. Here's a nice long article for a very in-depth description of why you are seeing what you are seeing: http://www.allaboutcircuits.com/vol_3/chpt_3/4.html

Why not just buy a standard wheel horse regulator and wire the AC from the stator into it, and the resulting regulator output into the existing electrical system?

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JUSS10

thanks, I had actually done some research and found that info as well.

you know, i used to have one but it went with another tractor of mine, i could build one for less than $10 and mount it on an aluminum heat sink, i guess if i could find one for less I'd be all for using a wheel horse one...

thanks!

Justin

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wheelhorse656

Diodes change the current from ac to dc and lower the volts as well i would stick with the diode set up they work better than you think!! :thumbs2:

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Lane Ranger

JUSS10: I converted two of my old Tecumsh H-60 rectifiers using Ed Stoller's posting on using new diodes. I have attached the article but the photos are also availalbe on the web. I did this and have very little electronic/electrical experience and it worked on my tractors.

The article is on the web at:

http://home.earthlink.net/~edstoller/id11.html

5-12-0 General,

Some of the older Tecumseh engines had a small stator under the flywheel and the Rectifier assembly on a board as shown in Figure 5-12-1,H 60A.jpg. Often the diodes fail and are no longer available, so this section is about how to replace the diodes with ones that are readily available, Figure 5-12-2, H60B.jpg. The circuit diagram is shown in Figure 5-12-3, H60Dia.jpg.

5-12-1 Replacement:

The original diodes were held in place with a fuse holder like clip that are riveted in place. I drilled the rivets out and replaced them with 4- 40 screws. The clip was replaced with a terminal lug shown in figure 5-12 -2. The replacement diodes are 1N5406 soldered to the new lugs. It is important have the banded end of the diode towards the fuse. Radio Shack has 3 Amp diodes; there 1N5402 has a 200 Volt rating which is a comfortable margin. If the original clips are held tight, one could solder the diodes directly to them.

Figure 5-12 - 2 Testing:

To test the complete system, disconnect the wire to the BAT + terminal and run the engine at about 3000 RPM. You should measure about 14 Volts DC at the BAT+ terminal. You can also measure the AC voltage across the two GEN terminals, about 30 Volts AC. To check the diodes, shut the engine down and disconnect the wires to the GEN terminals. Most newer multi meters have a diode test function. Using this to check the diodes, you should measure about .5 Volts in one direction and open in the other direction ( by reversing the red and black meter leads). If you don

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JUSS10

Thanks Lane, that had crossed my mind but wanted to see if someone else has done. off to radioshack in the next few days to replace the old diodes! :thumbs2:

Justin

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Lane Ranger

Some chatter on the web on some website also said you might be able to bump up the diode from 3 amps to 5 or so if I recall.

Ed Stoller and I traded a couple emails back and forth when I did mine two years ago.

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JUSS10

so i was thinking a little more about this, for now i will change up the diodes and solder in some new ones, but would a later model regulator/rectifier work better across all RPMs? i dont recall what the AC voltage output at idle is but with the current rectifier setup, the engine essentially needs to be at full RPM to even get the DC voltage output to be above 12v let alone the 13.5 that is ideal for charging.... would a regulator/rectifier be more efficient for charging the battery at any RPM? just thinking out loud here...

Justin

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JUSS10

i just looked, radio shack does have some 50v 6amp diodes... being that the motor shouldn't put out more than 30vac i suppose those would work and up the output amperage granted the AC voltage going in can output that much...

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