Ilford enlarger head, that keeps blowing the lamps in the high contrast holder. I found that the metal baffle plate part to prevent light coming in/out of the exhaust vents had largely closed off the associated vent, so suspect that was the cause. It had moved, because a plastic part had been warped by the heat over the years. The similar plastic part on the other side was also warped, but the plate was still located correctly.

A thorough cleaning out of the cooling fan area would be a good idea whilst in here. The warped plastic parts were sort of reshaped back, with a hot air gun and some blocks of metal. Other measures may be deployed to stop the plates from moving in future.