I checked for continity the D+ and D- from end of usb cable (the one that goes to the PC) to the leg of the pic. They are soldered correctly.
About the midi DIN5, it is not the same to connect pins 4 & 5 than 5 & 4. Pin 1 of megadrum board must be soldered/connected to... the left pin of the DIN connector or the right one?