You might remember this rather unhappy Japanese Sega Saturn from a little while back. The disc appears to spin backwards while the laser assembly goes completely berserk, and the motor sounds like it’s trying to escape from the CD deck. I bought the poor thing as faulty, and it certainly hasn’t disappointed in that department!

I’ve been having another look at the drive board to see whether I can work out what’s making everything behave so strangely. One component that’s caught my attention is the BA6798S on the left-hand side. It’s a ROHM four-channel H-bridge BTL driver, which is responsible for driving various motors and actuators in CD mechanisms.

That makes it rather interesting when I’ve got a CD deck with a spindle motor racing away and a laser assembly moving all over the place. Could it be the problem? Possibly! But I haven’t proved anything yet, and there’s still the servo and control circuitry to consider. It could just as easily be something else telling the driver to behave like a maniac.

For now I’m putting the white Saturn back on the shelf while I wait for parts and work out what to investigate next. We’ll make you better, faster, stronger! Or at least get the disc spinning the right way, which would be a pretty good start.

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