One of them was "fat", an obvious sign to the trained eye that the Lithium-based battery inside has gone bad. So .... an excellent candidate for looking inside! The second specimen does not hold the charge, so I think it is going down the same road of its brother.
I didn't expect fancy technology, and I was surprised I could read markings on ICs: (RDA)5807M I2C FM radio and AK2117C "Artek Digital Multimedia Chip" (an 8051-like MCU with multimedia I/O).
While looking around the board I noticed a strange "white" component behind the 3.5 mm audio socket. Looking closer I saw that it is a pushbutton! That's why in the picture there is a small screwdriver stuffed into the audio socket.
I tried to push it on the still-intact yellow player and it seems to act as cold reset button. Probably it works for something else too, like triggering firmware update, but I don't really care.
Still, that button has been hidden in a very smart way!
By the way, the RDA5807M chip tunes from 50 to 150 MHz WBFM!
