Sorry, I was confused. Now this makes a bit more sense. I’ve also had this issue with SCSI2SDs before. You are hooking it up internally or externally? Do you have a spare SD card you can test to format on this SE/30? Any other real SCSI HD to test? I’ve had to set up individual SCSI2SDs before on various machines to make it work well. Just ruling anything else out...using a SCSI2SD is a whole different thing.

As previously stated the device I'm testing with works fine on another SE/30 and Mac Portable. It's a SD2SCSI and the filesystem was created on the other SE/30. The drive was just moved from one machine to the other.
  By one drive I thought you meant one drive connected at the time rather than a particular drive.

Resolder the logic board? That's a no no for me, I can barely resolder the analogue board, I guess I'll have to find someone who's gonna do the job... Also other weird thing that happens with the picture is that over time, the picture just becomes wider, you can't see it expanding, you will only notice it when you use the Mac for a few minutes. Any pointers for that?

It’s possible it’s just the disk itself. I once had a bad HD that caused that very same issue: Bad Disk Name

All recapped now including C1, boots up loud and clear (i.e. the sound is fully functional again). I did clean/reflow any badly corroded pins I could find, though I didn't touch the Sony IC's, which are looking just a little green on the top side.   Anyway, all good in the hood. I was going to ask whether or not I should recap the analog and PSU as well, even though I'm experiencing no issues, but I think I'm just going to go ahead and do it as preventative.