For those who are into electrics/electronics, and can make out the Dutch language, there is a quite interesting article on another forum: “https://www.circuitsonline.net/forum/view/135679” discussing the original (Ducati) rectifier/regulator, including schematics. Also giving an in-depth test and discussion of an after-market alternative from Silent Hektik. I am now trying to convince that chap to run the same tests on another alternative, the one I use, which is from one Mr. Schicke, also German.
Thanks for the link, Jan. I can’t read Dutch but will translate it later. I suspect I will find the details interesting.
The Ducati PM alternator regulator/rectifier used by Rotax was originally developed as a motorcycle part. There is a long history of Ducati RR ‘issues’ going back to the 70s (on motorcycles using them with various roughly 150W to 450W alternators) and it might be worth noting for general interest that while the various types of Ducati motorcycle unit (including those supplied by Ducati Energia, a separate company since the ’40s) may look quite similar, they are not always interchangeable. Single phase versus three phase, substantially different power ratings and so on. I just replaced one on a motorcycle, this one a difficult to obtain high power single phase version and I hope it lasts for a while this time.
I don’t have personal experience with the Silent Hektik replacement units, or other direct replacement alternates either, but on an aircraft with electronic ignition I’d be looking to use something different than the Ducati RR to maintain battery voltage. Japanese motorcycle units would be on my list, but not many were designed for use with a single phase alternator. The schematics shown on the link are for single phase motorcycle alternators, is single phase correct for a Rotax 912?
Silvaire wrote:
is single phase correct for a Rotax 912?
Yes. On the back side of the 912 there is the usual flywheel, and it carries magnets that rotate near a series of pickup coils. Four coils drive one ignition curcuit, four more drive the other ignition circuit, 2 coils charge the battery, one coil drives the engine tachometer. The spec for the charging is “250 watt at 5800 rpm” with no voltage specified; I suppose the coils are connected in series.
The rectifier/regulator from Silent Hektik would be quite suitable for your motorcycle application; if only because it can take a lot of abuse; as confirmed in the test report. It also offers much better cooling. The article states that the original Ducati stuff is so poorly conceived/built that some components, the diodes in particular, would get so hot as to unsolder themselves from the circuit board… The Silent Hektik is rather expensive, though, upward of 200 €.
At least the Ducati Energia RR isn’t providing power for Rotax ignition!
There are several replacements available for single phase Ducati RR, Electrosport is another. For some of the lower powered single phase alternators people just use two input wires of a reliable Japanese RR that’s available used for next to nothing. My ‘problem’ is that I don’t like to chop up the OEM wiring harness or change the mount, sometimes the replacement won’t fit under bodywork, and typically I’m in a hurry, so I just buy another (lousy) Ducati replacement – which depending on model can be more than Euro 200.
There are a couple of active threads on Vans Airforce about Ducati failures and using the Silent Hektik:
http://www.vansairforce.com/community/showthread.php?t=144428
http://www.vansairforce.com/community/showthread.php?t=130921
It looks like the Silent Hektik is a very good replacement and I may go for one from the start when I get to that stage with my RV12 seeing as how many Ducati regulators seem to fail.
I looked at the two schematics in the first post above. What an utterly crappy design. For a start, putting a zener in series with the base of a transistor will ensure that the knee voltage of the zener will be poorly defined. I am not sure what the circuit is supposed to do, but whatever it does do, it won’t do the same thing twice, especially over any temperature range 
@wigglyamp: you might wish to consider the Schicke design, too. It gets good reviews and is much less expensive. I have one on my own 912 and it performs flawlessly.
http://www.schicke-electronic.de/dgr3tech.htm
Should you be in a hurry, I have a second one lying around here, it is available.
@Peter: the design is certainly crappy but I think the “analog” characteristics are not very relevant. Aren’t those transistors configures as a kind of Schmitt trigger, which is either on or off? The function is to fire the thyristors so as to charge the battery; firing them sooner or later depending on the control voltage at the “C” pin. As the output gets solid damping from the battery a crude regulation is sufficient. But sure enough the Silent Hektik alternative is superior in every way.
Silvaire wrote:
My ‘problem’ is that I don’t like to chop up the OEM wiring harness or change the mount, sometimes the replacement won’t fit under bodywork, and typically I’m in a hurry, so I just buy another (lousy) Ducati replacement – which depending on model can be more than Euro 200.
@Silvaire the Silent Hektik is plug and play, no need to change anything in the wiring. I have it installed in my Europa and it does what it is supposed to do for a couple of years now. It costs 197 € http://www.silent-hektik.de/UL_R_912.htm
@europaxs, Silent Hektik RRs are not plug and play for my particular application (which is a Ducati Motorcycle).
Electrex in the UK is another well known supplier. They have versions for most of the Ducati alternator confurations including single phase and also the unusal center tap three wire configuration that isn’t used by Rotax.
Silvaire wrote:
which is a Ducati Motorcycle
Ah okay, I only know that regarding the Rotax. However I can recommend to have a chat with Toni Kurpas, the manager of Silent Hektik, who is an absolute expert on this sector and modifies also Ducati motorcycle-electric (actually he started his business with that).
