Actually, it looks very simple for an enlarger power supply. That is a ferro-resonant transformer (the big thing with brown coil windings), which works with the capacitor (the other thing) to regulate the voltage. These capacitors frequently fail, and my guess is that was what happened. You can probably replace it easily, but the value (microfarads and voltage) is critical, and you need to replace it with something with the same ratings. As for the computer power supply, it looks like that would work fine. Your enlarger does not seem to have any strange circuitry, just a regulated power supply and a lamp. Before you buy the supply though, check to be sure the power wiring goes righ to the lamp and that there are no additional electronics in the enlarger. If there are, you may need the regulated ac supply, not the dc you get out of the computer supply. You may be able to find a local electronics hobbyist of ham radio operator who can help you.

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