@moira The buzzing is probably coil whine in the transformer, from some subharmonic of the switching frequency that happens to be in the audible range.

It's possible there's a bad capacitor somewhere, like in the feedback for the controller, or if the power transistors have a snubber circuit.

@toroidalcore it seemed too low pitch for transformer whine but I didn't think about lower harmonics so maybe that's it

capacitors are easy to check, at least. ^_^

(this is not the same model as the one with the splody cap and the values are all different so ... sure hope I have some lol)

thanks ^_^

@moira You can get weird effects if something goes a little bit unstable, or unstable during certain load conditions. It's kind of hard to say without poking around with a meter or scope.

Good luck!

@toroidalcore @moira if it sounds more like buzzing, it could be the core laminations becoming, er, de-laminated. try squeezing the core (in the direction that squeezes the laminations together) and see if that helps at all.

admittedly this is more common with older, larger transformers.

@wohali @toroidalcore oh it's buzzy for sure

i'm kind of afraid of operating it with the case off given the previous [POW] incident tho'

@moira

Do you have access to an oscilloscope by any chance? I'd be curious what the output looks like when it's doing that.

@wohali

@toroidalcore @wohali well guess what's not making the noise and not cutting out anymore

so it must be heat dependant and there must've been some heat even tho' i didn't feel any

@toroidalcore @wohali WHELP we're back

big voltage drop and the buzz, gimmie a sec for recording

@toroidalcore @wohali and it's leaking 60hz (at very low AC voltage) at all times, I didn't check that before

also I thought the buzz was higher pitched than I'm hearing now but I could be just remembering that wrong

@moira

Is that AC-coupled? That looks like the AC component on top of the DC output. What DC output voltage are you expecting from it?
@wohali

@moira @toroidalcore that's not terrible AC overlay, but it could be improved with better output filtering.

i assume you're not getting the voltage you expect here? or is it just a buzzing?

as always with these things, suspect the electrolytic capacitors. look for any leakage or funny smell.

here's a very good intro video to how SMPS work if you need one: https://www.youtube.com/watch?v=3FyXqNcqvRM

@wohali @toroidalcore oh now when it buzzes it's dropping voltage like a mofo

and quick, too

this is all new, none of this was happening until this afternoon so something yearns to fuck off into the sea

@moira @wohali I second the electrolytic caps having a good chance of being the culprit, but if possible it would be interesting to look at the switching signal to the transistor, and maybe the feedback.

I have to go to sleep, but will check in in the morning.