On Sunday, January 24, 2016 at 10:16:22 AM UTC-5, Cursitor Doom wrote:
Yes, the voltage across that power resistor looks very different when
scoped. No clean pulses at all; just constant NOISE and lots of it up to
about 20 or more volts so no wonder it was getting hot.
I also scoped the pwm output from the controller chip (TP.2 on the
diagram) and it looks like it's outputting a pulse train but is totally
overwhelmed by noise which I would imagine must be virtually saturating
V1812 resulting in a close to 100% duty cycle at no load.
Clearly major stability issues here.

At the risk of raising the ire of some contributors, I've found over my 45 plus years in the trenches that electrolytic capacitors can pass an in circuit ESR test and still be bad. It is an extraordinarily low percentage to be sure (although in Mitsu DM boards it's typical), but it's still a probability.

If I had that supply on the bench, I'd pull every cap and test for ESR, value, leakage, and dielectric absorption.