Hi,
I have been using chinese built 2.1 boards (2x devices) for some time without any problem. Recently I have come across several where the output filter inductor (typ 10uH) overheats to the point of blackening. I now find all the units from different suppliers are doing the same. I have tried replacing with a 10uH bournes 2101-v-rc but this produced no improvement. When supplied from a 24V supply (24.2V) with o/c loads the board takes 400mA (2 devices remember) cutting two (bass one complete device) drops it to 180mA, running on one is 100ma and all removed is 50mA. Checking output frequencies I get 400kHz on one device and 120kHz on the other. Bizarrely, using a known good device the output frequencies are the same (which astonished me) but the no load current is 70mA, about where it should be. When connected to a loudspeaker system astonishingly it seemed to work quite well, until the smell of burning PCB makes you turn it off that is. Anybody got any idea what's going on?