Good morning everybody. Unfortunately my Durst Laborator is having bad problems. It burned out three replacement lamps in few minutes. I suppose the problem lays with the power supply unit EST 450, probably the stabiliser isn't working properly. The very strange thing is, however, that the lamps seem to be UNDERpowered. When I replaced them, everything seemed all right, perhaps just a bit too dim, at the beginning, but within a minute or so the light began getting dimmer and dimmer until the lamp failed and showed a glass all covered by a grey-black powder. Also, I measured the voltage fed to the lamp with a high quality tester and, without load, it read 21 Volts AC rather than the expected 24. Does anyone know if these 24V 250W halogen lamps can fail for undervoltage? Perhaps by poisoning the gas inside the glass bulb, or by ionisation or such? It's such a strange thing. Also, does anyone experimented something similar and can guess which component inside the power supply can be faulty? It's quite a complicated circuit, very hard to figure out, but none of the components shows obvious traces of damage. The head fan is working properly, so I would exclude a problem with overheating. Lamp failure also happens too fast to be due to overheating inside the head. Thanks to anyone who will help to find out what the problem is.