Magnetek 3230 power converter problem

Thanks everyone. The filtered and unfiltered power makes sense, but I now have some new information that may help... looking at some of my pictures taken on a different angle, I now see that the main battery negative lead area is corroded and burnt. I guess the bundle of white wires had been blocking my view. I have a feeling my friend may have briefly reversed polarity when he installed his new batteries recently. I now regret that I didn’t check actual voltage, as opposed to simply presence of nominal 12V at the battery and fuses. I can hear it humming faintly when the circuit breaker is on, but I’ll bet the converter is fried.