I have been using plenty of STM32F4 discovery kits for my PhD research project. Now I received bunch of new version (rev. D) and found out, that if powered from external 5V, the MCU does not boot up. If the USB is plugged to CN1 and removed, it is OK.
I tried few boards and all are the same. It does the same thing even with the original demo software (freshly unpacked PCB). I had no issue like that with the revisions B and C. Please advice.