Whilst I'm thinking about it - worth a sanity check on the cooling to the laser tube - my inlet/outlet on a cheap 40W Chinese special were swapped (fed through each other's holes in the back of the enclosure) - the water inlet is supposed to be on the lowest point on the tube and the outlet is on the highest part of the tube - to ensure that once coolant is flowing that it completely encloses the laser cavity (and thus cooling it). If you get those the wrong way around, the water flows in from the upper inlet, and drains out of the lower outlet without being able to form the water bath to properly cool the laser.

It's the work of a couple of minutes and (thanks to the Chinese manufacture) a single screw (from what I recall) to visually confirm this before risking damage to the tube.