Some time ago I asked for donations of dead R/R units to analyze. Two units, both early BB units were received. These units have the soft RTV potting compound on top, no fins like the later version in my 03. While I have heard of late model units failing, I have not seen any to analyze.

Underneath the RTV glop is the wiring to the plug, while the actual circuitry is under another layer of epoxy looking compound. I don't think it is practical to get thru the epoxy and examine the electronics. So my observations and conclusions are a bit limited.

I measured the units with a curve tracer, a device that shows the voltage and current graphically.The indications are that the rectifier diodes are breaking down and shorting. It appears the regulator part of the circuit is still functional.

The diodes breakdown and short, when the voltage applied is around 20 volts. The diodes should be able to withstand whatever peak voltage appears from the stator, this could be easily up to 100 volts. The stator coils will have very large currents flowing when the diodes short, this is why people have seen the plug melt and also the stator fail.

The diodes would appear to be the weak link, and most likely are not properly rated for this application. I do not believe that the power consumed by the bike is a major contributor, as this appears to be voltage and not power related. However, most electronic failures do have a temperature dependency, and it would be prudent to keep the unit as cool as possible. On these early units the entire heat conduction path is through the bottom plate, it would be a good idea to have some thermal grease applied to the bottom to help conduct heat to the bike frame.

Having now seen the same failure mechanism on two units, I have to believe that the early R/R is inadequate and probably should be upgraded before blowing out a stator.

Thanks for that evaluation.

Are you gonna build us a super-duty better one?

Thanks for the write up----much appreciated. I swithed to an R1 unit when mine went out. Used thermal grease on it and was good for about 4k miles. That one a diode fail-----so I mounted the next one on a heat sink from an electronics store-----though I did have to mill a couple of fins so it would fit under the bodywork. Been doing great for several thousand miles now.

One thing I noted as I was checking out and changing the last one-----I hadn't done a very good job of tieing up the wires so they wouldn't vibrate loose. They can not move with this last installation---so fingers are crossed. Mine is a '97 with right at 42K now-------------happy trails kel

Good work Mike!

I've heard news of a revised '97-8 finned version from Honda of the R/R... Is there any truth in this? With ~40k on the bike, on original equiptment, I've been thinking of taking the current one off and replacing it with the "new" version and taking the original one with me as a spare...

Also, when I was working for an electronics company for a college internship, we used old/shitty soldering irons to bake through the potting to get to the electronics, to reverse-engineer other people's stuff... I mean... uh...

Mike

I just replaced the R/R on my '97 last year with a brand new Honda OEM one. Yes Mike, you are correct. The new ones now have good fins on them and the mechanic at the dealer said they have "beefed up" the new ones. If this thing fails in the near future I will be very disappointed.

I would be interested if there is any difference in longevity between OEM Honda and Aftermarket ones I see on e-bay.

I've heard aftermarket R/R's are worse than OE...

Mike

Edit: SHIT, even through servicehonda.com, the replacement part is $160... and if the R1 R/R's are $60, then I could get (2) to have 1 as a spare and still be $ ahead! Damn!

I'm thinking of building a better one. Problem is that it takes a lot of time to really be convinced you have a solid design. If I do design one, it would be more for the purpose of maximizing output. I think by using a synchronus rectifier of mosfets instead of diodes the efficiency would improve a bit at low speeds. We'll see...

How does the unit work? Is it just a 3-phase rectifier and a following regulator with a fixed voltage and fixed max current, or something smarter? Wouldn't the easiest solution be just to use a Rec/Reg from a bike without this problem? I man they all seems to have three alternator windings and about the same raw-voltage.

I've got to agree... it's like they told us in school... "look around... if there's something you want to make, chances are, somebody's already made it, and you can buy it for $0.20 in a single chip"

I too had thought about making a R/R, but honestly, with the majority of the operation being in the linear region of the FETs, you're probably not going to save a whole lot of power/heat by going to FETs over the transistors, and you can buy the R1 R/R for something like $62, and frankly, it'd probably cost $80 or so to do one yourself, once you got the big heat sink and everything hooked up, and on a PCB and everything...

IMO, not worth my time...

Mike

R1000, don't know your name,I'm pretty sure it is just a 3phase diode block and linear regulator following the diodes. So yes, just getting any other unit that is good should be the smart thing to do.

Mike, None of this is worth it's time, I just like to fix and build stuff
But I was not talking about changing the pass device to a fet, I am thinking of using a fet instead of diodes to minimize the voltage drop. This should help the low rpm operation where the diode forward voltage is a significant part of the total available voltage. But this requires a control circuit to trigger the fets,much more complicated than diodes.

Gotcha... I thought you were talking about changing the reg part to a FET...

I like to build stuff too, but even though my degree is in EET, I still would rather fabricate something out of metal... but that's just me, and to each his own...

Mike

Nerds!

Me too, that's why I have a Bridgeport mill in my garage I would mention the lathe, but it is an antique Rivett , turn of the century (not this last) and not too usable as it sits now.

Also a gas welder that I need to get better with, a hydraulic press, band saw, a proper drill press and lots of hand tools

Oh, and a wood lathe and router table. Wonder why I'm single

GAY NERDS!

Also make homebrew, you pussy.

None of that carb cleaner you snowbound louts like to suck down