I had a similar problem once, but without an IDE-Fix (or similar) board attached. What happened was, I had a homemade VGA monitor adaptor and a monitor that had trouble syncing occasionally. I managed to short something in the VGA adaptor (by being stupid), and bang, my A1200 went dead. The Short 2.5" ribbon cable to the hard drive looked exactly like the one in your photo. I had someone else look at it, and he got it working again, but for some reason an accelerator couldn't be connected anymore (more damage somewhere). Fortunately he had a replacement that worked with my accelerator.
What's strange is that a fault in a non-related part of the machine caused the cable to burnout like that. I never really investigated further as I was just happy to get it working again.
Hans
