KRK RP5 no sound when cold

Hey guys,

so I've had these KRK RP5 monitors for a while and one of them is only working when it has warmed up and I can't really figure out what the problem is. When it's cold,there's a lot of noise and a little buzzing with just a hint of the audio signal that should be played. After a while, the signal gets louder and the noise disappers (apart from the normal noise floor of these monitors, which is pretty high anyway).

I switched out quite a few caps that looked iffy, scraped off the infamous hygroscopic "black gunk of death" and replaced a few rusty resistors that had fallen victim to it. I also reflowed the power transistor's connections for good measure, but the problem still persists.

To me it seems like maybe there is a cold solder joint that makes a connection again, when the solder gets a bit warmer? But I can't really see any obvious ones. So my question is: is the any part in particular that would exhibit this behaviour with a faulty connection or smth. that I could specifically look out for? Or am I barking up the wrong tree and it's something else?

Best
Jannis

I know transistors like to act up in relation to temperature changes more often than other components in my limited experience but who knows.....

Maybe take some readings from your good amp and compare???

Maybe this is interesting for you:
https://www.youtube.com/watch?v=dftkoD7LG0A
EEVblog

Thanks for your replies!
Yeah I've seen that video before, but, apart from it being kind of entertaining, it doesn't contain any hint at a solution to my specific problem.

Transistors might be a clue. I just thought that it might also be a problem with the power supply not delivering the required power to the transistors from the get go (which would most likely hint at another capacitor fault or smth.), could that also be a possibility? I'll have to check what the operating voltages are on the working one, I guess.
Btw. does anyone maybe have a schematic of these things flying around? Can't seem to find it anywhere online.

Best Jannis

Use "Freeze spray" or in a pinch, at least here in the States, canned air when turned upside down, will spray out a very cold substance. you can use that to cool components to see which one is causing the problem. You can also use the tip of your solder iron to do the opposite and heat things.