agentz

This is probably a long shot, but we had something similar with our set ups in our primaries... about 18 months ago we rolled out a batch of Dell E5510's without any issues. We then replaced a bundle of projectors with NEC NP310Gs and a number of users started reporting 'jittery' cursor movement, and jaggy horizontal lines when drawing on their Smartboards. Like you I eventually narrowed it down to only happening when the VGA cable was attached. Turns out that the previous projectors had been grounded, the NECs were double insulated, and the E-port replicators we'd just put in were also DI (they shipped to us with the two-pin version of the mains jack, randomly the next batch had three-pin sockets on the mains input side). Some weird ground loop interference I guess. Was able to prove it to one of our sparkies who was very sceptical about it by using an anti-static wrist strap (the sort that clips on to a yellow plug) and croc-clipping it to one of the thumscrews on the VGA connector. Eventually convinced our property maintenance people to re-wire VGA sockets to ground them properly for any users experiencing the issue.

Hi Neon and everyone else with the same issue. Not been on here for a long time but I just want to give you a huge thanks for this solution - I've had a couple of users report the jaggy line problem after having new NEC projectors installed to replace failed Hitachis. I was kinda sceptical the first time when a teacher insisted that the problem only started after they got their new projector installed but after finding this thread and earthing the VGA cable as suggested the problem went away I hunted round the school and found a Dell power supply with an earthed mains cable and attached it to their port replicator and the problem got significantly better but didn't go away completely. I'm now speaking to our electrical maintenance team to get a workable, easily deployed solution as we're just about to place an order for a couple of hundred NEC projectors to replace ageing Hitachis and I can guarantee more teachers are going to have the same issue. So, once again thanks to Neon and others who helped me with this issue