Blown fuses are generally caused by an intermittant short. The only other possibility, could be a sticking solenoid, which could cause overheating of the circuit. In my early years, I used a 70mm rollfilm camera for portraits, and the shutter solenoid would occasionally stick. It caused me a lot of grief until I figured out that was the problem. Test the solenoid first, if that isnt the problem then check for shorts.