I have that Omega too, and there may be something intrinsic to the Omega timer that could trip a GFI. Looking at the schematic, you can see that there is a voltage-buck/boost winding on the power transformer with a series capacitor that will charge and discharge along with the inductive buck/boost winding. (It's the winding that does not appear to be connected to anything else). The initial power-on surge-backsurge through that buck/boost winding could appear to the GFI like a partial short between the neutral and hot line-input wires. Try the enlarger with all its accessories on an outlet that is not GFI-protected. If it works flawlessly, without any apparent electrical problems, the Omega may 1) either not be compatible with GFI outlets or 2) you have a very sensitive (low-current-trip) GFI. An electrician may be able to help with GFI outlets with reduced trip-sensitivity. Good luck - and you may want to obtain a schematic diagram for troubleshooting.