Today we spent an hour trying to debug some discarded audio gear. Among these was a Sharp SD-EX220 ”1-bit” (likely class D) amplifier/CD player.
When turning the unit on it would run for about one second, then turn off. Trying to debug the issue Tomas removed the logic and RF boards, leaving only the power supply and amplifier unit. Plugging everything in after this led to the latter releasing the magic blue smoke which makes all electronics work(!)
The culprit turned out to be the previous owner having bypassed the main fuse with a piece of copper wire, see picture below:
In short, the previous owner noticed fuses blowing and instead of having the unit repaired applied a dangerous hack. Lesson learned: always inspect your fuses!