i think you can find a replacement.. as long as it's the same spec as the one you have now, and the same connector... (i.e. just check to see that it supplies the same amount of DC voltage, and that that it has the same current rating...)
usuallly the supply has something that says "Output...
ok.. second harmonic.. i wasn't sure.. that's why i said ..it [might] be a harmonic of 60Hz.. which you just confirmed that 120 actuall is the fundamental though.. cause of the way the shit deforms.....
also, i thought i read 120Vrms, but i was wrong... nvm
OP:
if it's annoying you.. or if it still bothers you.. go ahead and get it replaced again.. just don't be surprised if the 3rd supply still makes noise..
the OP hasn't described if the sound is loud or low...
like i said.. if it's a low sound.. then it's probably fine.. if it's loud.. like annoying loud it's probably a problem and should be replaced...
i'm just saying..a very low whine is ok... that's it that's all
human range is from 20Hz - 20KHz.. i thought it was 300Hz to 20KHz.. my bad.. so you can hear the 60 Hz from the outlet.. if you're young..
I think the other poster got mixed up.. the voltage coming out of the wall is 120Vrms, while the frequency is 60Hz.. so it would be a 60Hz sound...
it probably is a switching supply since they are more efficient actually.. i'm sure they would use that in a laptop supply more so than a basic rectifier PLus LDO regulator
They ALL whine to a certain extent.. if it's not that loud it's fine... sometimes the vibration is so subtle you can't hear it.. but if you can hear it.. it doesn't mean it's fucked up.. do me a favor and walk around a power station and you'll hear loads of vibration from all the transformers...
again.. it depends how loud it is... if the room needs to be completely quiet to even hear it.. it's probably ok.. i've seen that with many laptop supplies as well as PSP supplies.
WOW.. capacitors squealing? that's something hahah... are you sure it was a cap? normally they just pop, or...