Thanks for the warning and your research on the issue. I am sure it will benefit anyone who has such a broken cartridge, especially when the code is available for reprogramming.
That is quite unfortunate and sad... Not sure what is wrong in your case, I've been able to use the slots almost all days with my SM-X, I have PowerGraph 9990 Lite and a OPL4, both from Tecnobytes, which are working good, just hope this is an issue with your particular unit (which still is unfortunate) than a general issue. I didn't change anything related to it so it is like when it was manufactured in regards to slots (so no change to pull ups, etc), I'll let people know if I run into issues with it, and I think that it is good advise so if anyone else had failures, perhaps we can gather more information to try to figure out what is wrong.
After much effort and research I managed to convert the Moonsound PEEL into an easier to find GAL.
So, should anyone ever break their GFX9000 or Moonsound, know that I can now help you fix them.
Great news! Can you describe how to do that, so other people can also fix their device?
So good new you could get back it to life