I thought I had a problem with the video digitizer again (see other thread) but it turned out that the digitizer is working fine - if I connect an external source to the digitizer, the image appears in the VP SW crisp and clear. I checked the connecting cable from the VP Head controller board (wire attaching to pin 3 of 8P connector) to main logic board Head connector (wire connecting to J26, Pin 3). That cable is OK. It looks like there is no video output from the camera itself or there is a problem on the VP Head controller board. What should I do next to get this isolated & fixed?
I would try to connect the "video out" signal from the camera directly to the digitizer. This will verify the camera. If the camera is O.K., then the contact of the relay that connects the camera to the digitizer could be defective. This is quite a weak point of the mainboard. A relay with Au contacts would be suitable here. But the relay is a relay, eventually he dies.