I recently acquired an old Beseler Dichro 45 color 4x5 enlarger. It gets electricity when turned on (The fan comes on and the LED's light up on the front), but the main bulb won't come on even though it's good (I bought a new one to check it out). The contacts for the bulb are hot when tested on a meter, which is what is perplexing me. I have no manual for it and don't know where to go next. Any suggestions?