I had a problem like this with a digital copier/laser printer. The circuit controlling the fuser would go nuts and overheat. It never occurred in the lab. It was only when we saw a customer installation that had it on the same circuit as another laser printer that we figured out that they both created noise on the AC line. That was enough to confuse the circuit, which was looking for the zero-crossing point and couldn't detect it in the noise. Some small changes to the circuit and control software fixed it.
TomMasz
lemmy.world
TomMasz@lemmy.world