Trying to diagnose this one. A video is worth a thousand words right?
https://www.youtube.com/watch?v=KqdH2nx1DX8
I'm trying to determine what the problem exactly is. Troubleshooting guides point to things like bad horizontal sync oscillator and/or problems with vertical sync. This TV is a bit unique that it is a multisync monitor that can take both TV and VGA (480p) signals. Not shown in the video is occasionally the OSD oscillates in a sinewave pattern from not moving like in the video to very quickly and back.
Looking in the service docs (yes I have the service manual and schematics), the synchronization and H/V drive is handled by a Sanyo LA7860. I strongly suspect that chip has gone bad, or one of the electrolytic caps in the circuit is failing. No visible signs of leaking caps or blown components on the PCB that I can see. How the TV handles the OSD is quite complex (since its generated by the jungle chip, but the set uses an external sync driver), but its odd that its mostly working while video input is totally fubared.
This set was sitting for about a year in climate controlled storage and was working fine when last used. I turned it on one day and well, this happened. Normally I wouldn't bother, but this set is low hours and quite rare. It handles a wide variety of video game consoles and vintage computers with its RGB input.