480p/720p not working on Sony KV-34HS420

[brirec]

Edited this a lot. I wasn’t entirely sure what was wrong, now I have a better idea.

I just got a Sony KV-34HS420, and after mucking a bit too much in the service menu both 480p and 720p aren’t working for me. Interlaced anything works fine — I’ve tried 480i and 1080i and it looks great.

However, with 480p or 720p (or no input at all) I get either a garbled, flickery picture (with lots of purple and grey) that doesn't relate to what's plugged in at all that looks something like this https://imgur.com/a/rVtXU6U or I get a black screen. The OSD and service menu are visible just fine when this is happening.

I made the mistake of resetting all the NVRAM settings (service mode -> 7, 9, enter) but I put them back as far as I can tell from reading the service manual specific to this set and some further tweaking of those settings. I managed to fix everything else — geometry, convergence, audio, etc. but it simply will not show a 720p or 480p picture. Interlaced works fine.

I have no idea how to troubleshoot it further...

[brirec]

I hope that bumping this isn’t so bad. I spent all day trying to get this thing working again and I managed to get 480i and 1080i working just fine. I also discovered it’s not actually the HDMI that’s bad — this happens over component video as well, and also the “default” source of black nothingness — that shows up exactly the same.

So to be clear, on inputs 5, 6, and 7, (component and HDMI), I can only view 480i and 1080i. 480p and 720p, as well as a lack of input at all, switch it to some sort of mode with garbled, purple and grey output. Sound works, everything else is dandy, but it simply doesn’t show anything correct if I don’t feed it an interlaced signal.