I'm not sure, I am trying to tack it down, but haven't been able to find that exactly. I've checked all of the wires coming out of the CRT and they appear connected correctly. I think the unit took a blow to the side during shipping and am afraid there might be a broken solder joint or trace. Someone told me to get out the magnifying glass, but I don't have a lot of experience at this and am not sure I will spot the break.