Snow/static effect on video signal

[Mu.]

I'm running my VA1 via VGA and in the last month it's picked up a serious problem with static-like noise all over the picture. At first I thought it was my television but no other system I tried had this issue, I'm certain it's the console itself after running it through my GBS8200 upscaler and still experiencing this problem.

I've included a video of the issue to YT here:




I had a cursory glance at the signal path the VGA pins take from the AV port back into the system, the only components between the RGB encoder and the output are a set of 75 ohm resistors and a ferrite bead for attenuation and smoothing. I was worried that the RGB encoder chip (SEGA 315-6258) was dying, but after replacing it with a chip from a dead motherboard I'm no worse off than when I started.

I'm beginning to worry that this issue may be coming from somewhere further in the system, if it's in the Holly chip then I doubt there's very much I can do about it.

If anyone else has seen an issue like this and knows what the cause may be, please let me know. I'm already looking to get yet another VA1 board but really don't want to if I don't have to.