Garbled screen on HDMI, VGA is fine

[Jasper]

I had not used my DC for a while, turned it on and now the HDMI output it has this strange screen tears. Video from VGA is still fine. The DCdigital menu displays fine too.

Changing resolutions or switching firmware types will correct the issue. After turning the machine off and on again the issue reappears.

I have been using the dreamcast before without any issues. I updated the firmware though that didn't make any difference. I also reflowed all connections, didn't make any difference.

What's going on here, and more importantly, how do I fix this?

 

[Pink Skelly]

I’m unsure if it would cause the issue you have but many of those pins on the flex appear to have very little solder on them. If it was me, I would go over each of those points with a bit more solder or at the very least check for continuity between the chips and the flex points. I suppose it’s possible that thermal expansion causing one or more points to separate on the video side of the flex.