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My RPi B+ stopped booting suddenly after 1month working. I try 4 different usd cards and for all of them act (green) led flashes 4 time and no video and no power on usb ports and ethernet. I know it means start.elf not launched, but new NOOBS seems not having start.elf. I try formatted usd and act led is on permanently. Even I deleted bootcode.bin and act led is on permanently. So RPi seems have access to usd card and I don't know what the problem is. When usd is inserted clock pin of usd has no voltage (dc or ac). Can someone help me?