Ambika crash / freeze / glyphed out lcd (Solved)

Ok so my friend sent me his Ambika to look at. It was working fine for 8 months but now It keeps crashing. I can guaranteed crash it by going crazy on the mod wheel but it will crash at other times too. When it crashes it starts by flashing up a black dot on the LCD then the LCD starts showing weird characters like “-/n” and random shifting stuff. Eventually the audio will crash too. Ranging from a stuck high squeal to a super bit crushed distortion.

First thing I noticed it was missing the C11 100n cap for IC 4 so I added one I had laying around. I also tried swapping out the 6n137 chip (as recomended to me) with one from my own working ambika with no change. I just went through and checked the power and I am getting the correct readings across all the points listed to test in the assembly instructions. I also checked JP1, JP3 and JP5 and am getting the expected respective 8v and -8v on each one. The crash happens even with no cards installed so it is definitely the motherboard.

At first I thought it was midi as the mod wheel would guaranteed crash it but now I am starting to think it is the bus.

Any suggestions on what to check would be greatly appreciated. The fact that it worked fine for so long makes me think a weak joint might have cracked but I’ve looked over it and can’t see any obvious cold joints. An idea of where to look would be helpful.

Thanks peeps. Sorry for taking up your time.

While I was checking around looks like one of the cards has died too! I swapped them around and one is making no sound. Balls!

Don’t know if it was like that at the start or if something I did caused it? Maybe when testing the power? Although I think I had the cards out then. Either way as I can’t be sure I’ll have to give him one of my working cards :frowning:

I reflowed the majority of the motherboard and it seems to have fixed it. Must have just been a cracked joint after all. Hopefully it will keep working now. So far it seems fine.