Hi Jos,
I think I found an interesting bit of forum:
http://www.pilots24.com/pilots24/forum/viewtopic.php?t=7756&sid=542ce097cbdde3a5ceba2e5bd0d71c38
Scroll down to 40% of the page.
Writer Arrow is convinced that he has found the problem with the
912/Ducati regulators, as follows.
The regulating bridge has 4 elements:
2 power diodes MR2510 and 2 thyristors TP154E (obsolete) or 2N6504.
One diode and one thyristor in series conduct part of one half sinus of
the alternator output, the other diode and other thyristor in series
conduct part of the other half sinus of the alternator output.
The thyristors have TO220AB packaging and are mounted directly to the
housing.
The diodes have MICRODE BUTTON CASE 193 leadless packaging and Ducati
designed a mounting technique: both diodes with their cathodes soldered
to a small copper sheet, copper sheet mounted to the housing using
silicone foil heat conducting isolation; wires to the PCB soldered to
both anodes and the copper sheet.
Everything potted with a potting compound.
The problem is that heating/cooling cycles work the electrical
connections to the diodes loose. The symptoms are as follows: charging
ok after startup (13.8V), losing it after half an hour, but the warning
light stays off.
The writer has a diagnostic test using a battery and two 12V lamps to
check continuity under heating.
The writer has a solution: parallelling the diodes with an external pair.
The writer has notified Rotax and asked them what they had done / were
doing about the problem (January 2008). The correspondence can be
followed at:
http://www.pilots24.com/pilots24/forum/viewtopic.php?p=48297&highlight=#48297
Scroll 30% down.
The upshot seems to be that Rotax knows there is a problem but it must
be because units are operated above 80C. No redesign yet.
By the way, Jos, the MR2510 datasheet shows a forward voltage drop of
0.9 to 1.0V at 20A, the 2N6504 one of 1.3V at 20A. Your 0.6V is too
optimistic! Newer parts may be better...
I understand that Schicke and Silent-Hektik make a better product than
Ducati:
http://www.schicke-electronic.de/dgr3.htm
http://www.silent-hektik.com/Duc_R_Duc.htm
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