I have 4 chained ST50 instruments. The backlighting on two of them will fail pretty regularly. By that I mean it turns off. It can be turned on normally when it does that. (Recall that the ST50 backlighting can be started via any one of the chained instruments.) Raymarine said it sounded like a voltage drop. I checked the fuse panel and found a terminal screw loose. However, it does not appear to be it. The connections on the Seatalk backbone are so small I don't see how I can clean them up. Any ideas? *o Rick D.