brightness not consistent

[lonix]

Hi, I have a cheap eBay laser green colour, it's got a nice focused dot that can be quite bright at times but goes from bright to dull then bright again, I have opened it up and had a look at the circuit board and did some minor tweaks to the pot which didn't help the laser keep a consistent power output I think there was a mosfet on there does anyone think that the mosfet is dead?