Will contacted me directly and here are my replies to several posts above.
The common failure for Ducatti are the internal diodes. Ducatti uses a full wave
rectifier circuit which has two SCR (controlled diodes) and two conventional
diodes. The mechanical construction fails on the conventional diodes.
Electrically,
the diodes are connected to terminal G and terminal B so you can put external
diodes to substitute or replace the faulty internal ones. The original
diodes are rated at 1200 v and 45 A. You must also mount them on a heat sink.
If you use diodes, the heat sink will be at +12V. A better solution is by using
a bridge rectifier on a heat sink so the heat sink is electrically isolated.
The bridge rectifier is 36MB120A (Newark Electronics PN 48F1234) and heatsink
is Wakefield 403K (Newark Electronics PN 58F505). The rectifier is wired so
that the two yellow wires going to G on the Ducatti also go to the two inputs
on the rectifier (AC1 and AC2) and the wire coming from B on the Ducatti (output
voltage) is also connected to + on the rectifier. The terminal of the
rectifier
is not connected to anything. Wiring diagram is attached. The same diagram
shows the diode for adjusting voltage and the crowbar OVP.
There was also a question about adjusting the voltage when using a Ducatti. To
make the output voltage higher, just insert a diode in the C lead which is the
voltage sense lead. That will make the regulator think the voltage is .5 volt
too low, and adjust cause the output to raise .5 volt. I have this in place to
get 14.2 for my EarthX. A 1N4001 will work fine.
Finally, my overvolt protection is a crowbar style purchased from B&C. I have a
relay that connects the regulator output to the aircraft buss. The crowbar is
across the coil of that relay, so if it trips, it will cause the relay to drop
out.
There was a guy on the RV12 list that made a robust copy of the Ducatti
regulator
long before B&C produced theirs. I purchased the circuit board from him and
built my own. It works good and it will output 25 A all day long!
Jim Butcher
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