Thread: selenium rectifier

I have a harness 1970 and my silinium is 1974

What color wire put on what pol on the silinium

wire : red and green


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personally i would not even think about using the selenium rectifier..they just are not that efficient and is one item that should be discarded and replaced with a modern silicon rectifier...look on ebay and get a silicone rectifier with honda oem plug (about $25) and its a simple plug and play application..also make sure it is rated at least 40 amps (those alternators (AC current) put out a lot of amperage on these little bikes) and i would use a heat sink...clymer has the wiring diagram and its a simple process..i cant answer this without looking at a wiring schematic and if you dont have a clymer shop manual (or other) get one...

ps:$25 is cheap...digi key has the silicone rectifier for about $7 (not including shipping) but you have to get an oem honda plug plus wires plus shrink tube...add your time in and $25 for an upgrade that will offer immediate improvement is cheap (one of the few upgrades that is actually worth doing)

ps:there are a few sites on the net that say you can check the selnium rectifier using an ohm meter (continuity)...i dont buy it...you need a singal generator and an oscilloscope to really verify..luckily i have both and its readily apparent using those tools if the selenium rectifier is in fact functioning at least somewhat reasonably...for kicks its neat to look at the DC signal (aka voltage) out on the silenium rectifier compared to the modern silicone bridge rectifier...if you ever see this you can see how antiquated/useless those silenium rectifiers are..bottom line is they just aint worth repairing (or even discussing) and they all should go to the trash can of history..your battery will thank you and so will your bike

there are a few sites on the net that say you can check the selnium rectifier using an ohm meter (continuity)...i dont buy it...you need a singal generator and an oscilloscope to really verify..luckily i have both and its readily apparent using those tools if the selenium rectifier is in fact functioning at least somewhat reasonably...for kicks its neat to look at the DC signal (aka voltage) out on the silenium rectifier compared to the modern silicone bridge rectifier..

Huh? Not to hijack this thread but as a process electrician in a steel mill, I routinely repair BIG rectifiers which are controlled by smaller selenium rectifiers and the only time an oscilloscope is required is to make sure all are firing in proper sequence. I always test with my fluke!

personally I think selenium rectifiers are cool and if my bike have one from the start id definitely not replace it with something from digikey.

Just my 1/2 cents worth

Anyways the dratv schematics don't have 70 wireing so I just went to the KO which I'm guessing is pretty close..

The 2 wires shown are red and grn with red being on neg post of the rectifier.

Hope this helps

I tested my selenium rectifier on an HP4145B semiconductor analyzer. It seems to work just fine. Given the fact the lights on the stock bike run on AC, the rectifier really doesn't need to do a whole lot of fancy work.

I had several good years of riding with one. Seem to work nicely. If it works, why replace it?

To answer your question, the green wire connects to the green wire coming from the stator, and the red wire goes to the positive battery wire.

As far as the rest of the thread goes, MrD has you pointed in the right direction.

Without getting deep into theory, the selenium rectifier is nothing more than a diode, or, to put it simply, it's an electrical one-way valve. Current will only flow one direction through it. The output from the stator is alternating - a sine wave that goes positive, then negative, then positive, then, . . . well, you get the idea. The rectifier allows the positive portion of the stator output to flow into the positive terminal of the battery.

(Yeah, there are voltage drop issues and and current leakage issues, and I'm not even going into the electron flow controversy, so if there are any engineering/physics zealots out there well you can just forget about it!)

Selenium rectifiers on little Hondas generally work fine for their intended purpose, but they have a few inherent problems. They are somewhat exposed, and corrosion will sometimes ruin them. They heat up in use and sometimes the heat will eventually do them in. And, they are old technology. Face it, the Honda 70 was designed before solid state electronics were in common use, so the charging system is a bit archaic. But as long as they are working properly there is no reason to replace them, apart from a desire to improve the charging system, or an incurable need to tinker with things. I suspect that there are a variety of inexpensive ways to improve on the stock charging system, but to make those changes would require a good working electrical knowledge, or good instructions from someone who has done it before. Or a willingness to replace burned up parts and learn from your mistakes.

That's my 2 cents.

-kevin

Thanks for answers

I seach juste where on put the wire on my selinium

The selinium is same for the diode

the green in and red out when test on my tester

thanks

One member said that it should be rated 40 amps,its hard to believe that little alternater could possibly put out that much,is that a fact???

Originally Posted by knucklebuster2

One member said that it should be rated 40 amps,its hard to believe that little alternater could possibly put out that much,is that a fact???

yes there is a lot of current flowing out from those little alternators..therefore...use a heat sink if you ever decide to upgrade to silicone diode pack..i think i went with 50amp...plus heat sink..hafta check though

thats interesting but brings another question to mind,how can the wires handle 40 or 50 amps as small as they are

Originally Posted by knucklebuster2

thats interesting but brings another question to mind,how can the wires handle 40 or 50 amps as small as they are

mr honda hired compenent electrical engineers..wire guage is adequate to handle the juice..if not you would be going down the road at night and the headlight would go off due to roasting wires