Where is the fuse on this phone?

I seem to have blown the fuse on my phone by using a cheap portable usb charger - the phone still works fine if I replace the battery manually and charge it in a separate battery charger, the phone detects when it is plugged in to a charger or a computer's USB port (it even thinks it is charging), yet the battery level goes down - is there a fuse somewhere, what type, and how can I replace it?