Some of you may have never looked at the light inside the laser tube. Glass and laser does not absorb much visible light, so we are able to see the pink light. At low mA, you can see the pink light at the end of the laser tube; the light at mid section of the tube is faint. As mA goes higher, the pink light becomes longer. If you see thick/faint purple light at high mA, the laser tube can be bad.
When you need to transport a laser machine for repair, it is good to take out the laser tube. Even if the laser tube is not firing, we only need to test the laser power supply. If the laser power supply is good, the laser tube is very likely bad. A GSI laser tube survived in a machine after traveling 300miles; maybe the truck's suspension was good. You may not have luck with other brands' fragile laser tubes.
When water is not changed and becomes dirty, it is hard to clean even with steel wire. Using acid to dissolve them is not fun. It is wise to keep the water clean.