Hardware Insights Forum

OUCH.

I know -12V is rarely used anymore but do we really need to take the chance??? The oscillation only happening in some of the tests...that's mystifying. Given that such ripple on the main rails would be Fail Award-worthy, I think more than a 1-point hit to the rating is warranted.

I wouldn't be so surprised by them messing up something like LLC resonant, but a good-old forward converter...

(I won't be surprised if, before too long, forward converters go the way of half-bridge, as there were PC PSUs using it in 2001 if not earlier.)

I considered removing 2 points myself, but I just don't think that the real world implications are serious enough, at least not for the PSU's target audience. This is intended for a new gaming PC, not to replace your old P4's failed PSU. I would have no hesitations about using it in a new PC. The rails which will actually get used are still in spec with plenty of headroom.

I kind of fixed one of them. I removed one of the two 470uF -12V filtering capacitors, and added two fairly beefy capacitors in its place - a 3300uF and a 4700uF. It's back down to just under 150mV now, which is still high, but miles better than it was.

What series are those???

In the scope shot for test 7, the -12V ripple was at the double mains frequency, so capacitance would help with that. But if it doesn't stay in spec even with the huge capacitors you used...

The 3300uF is a Panny FC, the 4700uF is a Panny FR.

I can't figure out exactly what is causing it, though. I suspect it's some oscillation in the feedback loop, but my oscilloscope just isn't designed for probing around inside a PSU.