I have a Sony PVM 14M2U that I recently picked up that is not displaying a discernable picture, I'm guessing that I have some kind of horizontal sync issue. I've tried both composite video signals and RGB with external sync, both provide a staticy, jittery image where I can only see the colors of the image stretched jaggedly across the screen. I hear a high pitched whine that seems to come from the flyback when plugging in a composite video source or attaching the external sync plug with RGB.
Possibly unrelated to that issue is that the picture itself it's very dim, I have to turn the brightness pot to about 75% of max brightness to get a decent image.
Here is a brief clip of what the screen is showing. This is Super Mario Bros on an NES connected via composite to bnc.
https://imgur.com/gallery/ujjU9ER
Thanks