JUNK STEREO REPAIR UPDATE
Hi Vince,
some of those SD Card slots have two tiny contacts to detect that a card is inserted. Could it be that those pins have been bent/shorted by clumsy use and that the CPU is detecting a card but getting no response and that this is deactivating the USB port?
McBryce.
That's an idea. Yes I did see such a contact in the SD car connector.
Not sure that's my problem though, see as even when I put an SD card in the slot, then switch the input selector to SD, it won't read the card.
Also the CPU was having problems powering the USB port, with too low a voltage and not enough drive to support any load, not even my DMM. So there is something fioshy inside the CPU inside, like Dragon said.
Also, the stereo is MEANT to have both USB and SD card connected at the same time, because it can copy MP3 files from one to the other.
Still...I will take that stereo apart again and play with that SD detection switch just in case...