A bit embarrassed to be posting another F80/M80 issue, but here goes…

I have purchased an M80 for one of my nieces. It looks in stunning condition and plays absolutely perfectly. However, as soon as power is applied, there is a low level hum, which appears to be coming from the board. Doesn’t seem local to the transformer, and not coming from the drivers. Is something about to give up? It’s not loud enough to be annoying when music is playing, and from a few metres away you can’t really notice but it is definitely noticable when stood within a few feet.

I just plugged it in today and intend to give it to my niece this weekend. I think it is still going to work ok in her space but I don’t want to hand over something that might go wrong quite soon.

Any experience of what might be going on? My F80 isn’t buzzing, so it is not DC on the mains.

F80