Studio Beam Fan Blues

Hi folks...

I've had a problem crop up with my Studio Beams a few times now and I'm not sure what, if anything, I can do onsite to fix it up. Two of my three spares currently have logic cards that will not drive the head fans. The motors work just fine, the lamp will strike, and even the ballast fan is working, just not the head fans. The fans work when hooked up to my last remaining working Studio Beam, but I'm nervous to pull the logic card from my working spare and try it in one of the other fixtures in case the problem lies in the 24V power supply and it's frying something in the logic card.

Am I being too cautious? Any thoughts or tips anyone may have would be greatly appreciated. Thanks!
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