Xantrex/Sorensen/Ametek XPD Power supply - No Load Losses?

[robert_]

I just managed to get a Xantrex XPD60-9 60V,9A PSU that had at least one pretty obvious fault: a line filter inductor was rattling around loosely as both pins were sheared off right at the board. Fixing this was quite easy, and now i have a PSU that seems to work, however it has pretty ugly no-load loss, drawing about 45W at idle, with no output voltage. That doesnt look very healthy.
I sadly dont have any service documentation, but it seems to use a fairly regular boost type PFC (which does work properly) folowed by a phase-shift ZVT full bridge converter (Controlled by UC3875).
Primary FETs seem to get the majority of these losses, heating up to ~70°C with the fan speed increasing.
At increasing load, the efficiency approaches the specified 85%, and the primary FETs actually get colder.
Could be that bridge is hard switching at low load? Primary FETs are 4 IPP11N60S5, which dont look like a first choice for something needing a fast body diode (Qrr 7900nC!) to me. I dont really feel like trying to "improve" (maybe using some 60R310CFDA, 350uC ) that design, as it could go quite wrong.

I dont think it is supposed to be that bad? Does anybody have a PSU from that series (output V probably doesnt matter) and could just measure no-load power to compare?