Obviously it wouldn't work without ground lol :smile: but ground on the OPL3 board doesn't need the ground plane.
If you open the board in Eagle without the ground plane, you'll see there is also an almost complete ground trace, which is incorporated in the ground plane. So for most of the ground connections, the ground plane isn't actually needed for the connection. That's exactly why I decided I wouldn't etch a new board. I wouldn't have gone on if all ground connections were missing, obviously... Where a connection was missing (in two places) I added it.
Secondly, the test tone firmware is loading and running fine, and the mp3 is from that one.
So no, I'm not missing ground and the firmware is loading fine.
With the FM firmware (and only with that one) I have exactly the same problem as described here:
So what I meant was that it can't write the 256 EEPROM bytes. There are no errors in uploading the firmware itself, which runs fine and responds to midi and patch changes as it should. As mentioned in that thread, that error would only affect the default patch.
My question, which started my post, was if this output was typical for a dead YMF? Because if it is, I can probably stop looking for something else.