Update: Laser PSU confirmed dead. Here are some photos of the burn marks.
Last time the laser tube failed, we installed a spare tube and it still didn’t work, so we suspected the PSU and replaced that. When it still didn’t work we realized our spare tube had failed too. It’s a long story, you can read about it here. In any case we ended up with an extra PSU which was kept as a spare. So this morning @Katie and I swapped in the spare. This involved carefully splicing the HV wires. We cleaned up some of the other wiring at the same time.
TL;DR
The laser is working again, but it is not yet online for general use. There is a configuration issue in LaserCAD which may have been a contributing factor in burning up the PSU yesterday. Until we can solve that, the laser is out of order.