Low outut from alternator

[yosemite]

Hi
The 906 discharges the battery when running with lights on.
Checked battery voltage with engine running, no lights rises to around 13.2 volts, with lights on battery is around 12.4v and falls
Voltage output at alternator is around 15v ac , across the two yellow wires at 3k revs, with load disconnected, the voltage output from the shindengen reg/rect unit is around 14.5 volts with the output disconnected from the harness.
Battery has been changed to check if that is problem, but made no difference, all connectors have been checked cleaned or replaced if any doubt. Seems like part of the alternator has failed, as I am sure it used to produce a higher voltage output but cant remember, its been a few years since I fitted regulator, only the two yellow wires are connected to the reg/rect
Is there an alternative higher output alternator stator that will fit without changing the rotor?
Thanks in advance

[Mc tool]

alt ac output should be 40 - 50vac at 3000rpm and about 75vac at 5000rpm . Im pretty sure my 906 alt has 3 wires , 2 yellows and a red , anyhows you probly need to get an ohms meter onto the alt windings , they should be pretty low at 1 - 2 ohms and there should be no continuity to earth

[yosemite]

Will get a meter on it next week, was about 5 years ago that I changed reg rect, not sure exact reason red wire was disconnected but think that I followed instructions in the faq about fitting an electrex unit, anyway its been ok until last week.

[Mc tool]

The red wire goes to the end of the two yellows where they join , mine is connected to the reg because it was when I bought the bike , man ,that was the start of my Ducati education , never had another vehicle that needed so much "sorting " admittedly a lot was "previous owner '"generated stuff ( he was a sawn off little smart arse , I enjoyed showing him how well it went after I had fixed the reason he sold it )