PA50 Recifiier: Why?

Stupid question, but I haven't found the answer after searching for a bit. Why is there a rectifier at all? What is the purpose?

Re: PA50 Recifiier: Why?

Its supposed to help steady the light flicker.

Re: PA50 Recifiier: Why?

Downhill Harvey (OFMC) /

To make the current go in one direction. If you check for continuity, and it does check, switch the leads, and you won't get continuity.

Re: PA50 Recifiier: Why?

I know what a rectifier does, but I'm wondering what purpose it serves on the moped. It's part of the ignition system as far as I know.

Re: PA50 Recifiier: Why?

Chris Holbrook /

i thought the alt. generated electricity in ac & the rectifier swapped it to dc..

Re: PA50 Recifiier: Why?

Yes, but why? Other mopeds don't rectify, so why does the Hobbit?

Re: PA50 Recifiier: Why?

Chris Holbrook /

wow i thought all bikes did from the 49cc all the way up to the big boys.. learn something new everyday i guess.. i was under the impression that all ignition systems ran on dc, either 6v or 12v..

Re: PA50 Recifiier: Why?

Chris Holbrook /

i talked to my old man about this & he said if it doesn't have a rectifier it doesn't have an alternator.. it has a generator just like the old cars do.. ignition sys. won't work w/ curent flowing in both directions..

Re: PA50 Recifiier: Why?

But it does work fine without it. Old men are idiots!

Re: PA50 Recifiier: Why?

I think its for charging a battery.

Re: PA50 Recifiier: Why?

fallout Survivor /

What year is the PA50. If it was after 81 or whenever they put on the battery box you need a rectifier for the battery which is dc only. Interesting question to study up on magnetos driving ignition, generators, alternators and 2 stroke electrical theory. Old cars had DC generators. Now they all have ac alternators with rectifiers. Why the switch? And lawnmowers have magnetos with an alternating current....

Re: PA50 Recifiier: Why?

It's an 80, and as far as I know, had no battery

Re: PA50 Recifiier: Why?

Chris Holbrook /

here's why i just found an tech article because you got me really curious.. its pretty interesting.. all of em have rectifiers just some are separate & some built in..

http://www.electrosport.com/technical-resources/technical-articles/how-motorcycle-charging-system-works

Re: PA50 Recifiier: Why?

That's not true though. Maybe for motorcycles but most Mopeds don't.

Also, if you look at the pa50 shop manual, many of the wiring diagrams that have them have no battery.

Re: PA50 Recifiier: Why?

Oh yeah, if you look at the other geographies that had PA50 they may have had batteries where the US did not. I can't remember for sure from the diagrams I was looking at. Probably cheaper to mass produce a "standard" wiring harness and just have the rectum fryer on all of em. I took mine off, never looked back.

Re: PA50 Recifiier: Why?

Chris Holbrook /

did you read the article? it said that the permanent magnet alt. on bikes all produce 3 phase AC.. the alt. has to be able to produce enough power for the ignition sys & the lights at idle, what do you think it produces at high RPM? high voltage, the rectifier on a non charging sys just grounds the power it doesn't need.. thats what i got out of it anyway..

Re: PA50 Recifiier: Why?

That's a regulator. A rectifier is just a diode bridge that converts AC to DC. Hobbits have a separate regulator (just a big resistor actually).

Re: PA50 Recifiier: Why?

Chris Holbrook /

cool.. inspiring me to look stuff up & then educating me.. i love this site.. i thought they were the same thing, i didn't know it had a separate regulator.. i think i have a bad rectifier on my bike, i already replaced the coil & still have voltage going to the head light.. but no spark, new plug & plug wire to.. if its not going to screw anything up on my old 79 points bike i'll remove the damn thing..

Re: PA50 Recifiier: Why?

Jimbo Grand Daddy /

I have an idea that might make sense. Let's say you're a mechanic at the local Honda dealer. You work on a wide array of bikes. Some guy brings his Hobbit in for an electrical issue. You start to test with a multimeter set to DC volts, as you assume it is DC volts, because the larger bikes that you work on more routinely tend to be DC voltage. Your multimeter blows because of the different type of voltage. My uneducated guess would be for this type of thing. A kind of idiot-proofing for mehanics. Does this sound reasonable?

Re: PA50 Recifiier: Why?

Eehhhh, nice try, but that wouldn't harm anything. Besides, if they wanted to sugar coat things, don't you think they may have started with the carburetor :)

Re: PA50 Recifiier: Why?

fallout Survivor /

Old cars had generators that had deficiencies: the current passed through brushes which limited the output and cause a point of wear (due to arcing).

They then went to mechanical rectifiers then solid state rectifiers on alternators. Some ignition systems still are ac (ak magnito) like lawn mowers.

Re: PA50 Recifiier: Why?

Jason T Wrote:

-------------------------------------------------------

> Oh yeah, if you look at the other geographies that

> had PA50 they may have had batteries where the US

> did not. I can't remember for sure from the

> diagrams I was looking at. Probably cheaper to

> mass produce a "standard" wiring harness and just

> have the rectum fryer on all of em. I took mine

> off, never looked back.

my vote. cost over reason 9/10.

Re: PA50 Recifiier: Why?

So you run your hobbit with the rectifier disconnect....and the resistor in?

Re: PA50 Recifiier: Why?

Jimbo Grand Daddy /

Like I said. It was an uneducated guess.

Re: PA50 Recifiier: Why?

Seems kind of funny that they would go out of their way to cast a unique case for the pa1 just to prevent upgrading cylinders, but they would save a buck by making wiring schemes the same.

Re: PA50 Recifiier: Why?

couple maxims:

engineers are way smarter then us.

but they have to answer to the bean counters before the end users.

nothing is added without a reason ($$$ matters)

i fail to understand why they do a lot of things the way they do:

"a unique case for the pa1 just to prevent upgrading cylinders"

i doubt that is really the reason, they just didn't need to explain to the end user why.

in laymans terms, 2 inches of extra wire times 100,000 mopeds is a ton of money saved.

my best guess for the rectifier, to reduce eddy currents / backfeed.

still no clue to phase / polarity mysteries.

Re: PA50 Recifiier: Why?

Let me throw in my two cents even though I only slightly understand magnetos..first in reference to that interesting link above to motorcycle magnetos , three phase ac current , ac rectifiers please note in the articles diagram there are THREE SEPARATE COILS mounted on the magneto each one is 120 degrees separated. That's why there is three phase ac!!! Now my hobbit which I recently bought is not understood yet by me BUT my Vespa bravo IS starting to make a little sense, it has only one lighting coil so by definition it can only produce one wave of ac current! I suspect the necessity for a rectifier is related to both this and of course the need and or presence of a dc battery. The weaker the power output from a magneto the simpler the need to handle excess current. Thats why we need a supply of light bulbs since the simple magnetos do often put out too much voltage.

Re: PA50 Recifiier: Why?

Cosmo nPuch Stillstolen /

My guess is that the rectifier "smooths" out the voltage for lighting.

You don't want any of that 'tricitee going backwards and heating up something.

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