Hi guys,
First porst here but long time pinside reader

I have a weird behaviour on my metallica pro I got last week.
First important point: the machine was unboxed only 6 months ago by the former owner and he never did any work nor modding on the machine, so basically its brand new.

The problem: first thing I noticed while playing was that sometimes - (not always!!) I’d get Sparky triggered with a direct hit to the captive ball.
After some more playing I noticed some more passive triggering by other switches on the same row as the captive ball.
also the grave marker gets passively triggered. As a consequence I get random multiballs (GM and sparky multiball) out of nowhere.

Of course I did some sw test and with the diagnostic everything looks Ok, no false triggering.

I tried also reseating every possiblr connector on the boards and below Pf with no success.

Upon further playing I got the feeling that some switches on row #3 sometimes activate switches on row #4.

I dont think its a diode problem, otherwise I wont expect false triggering on several switches on different rows.. i’d expect the problem to affect a column rather than a different row.

What could be?? I have no more ideas and I’m starting to wonder if its a cpu board issue..!

Other thing to consider: upon first inspection, I found a pin on the boot chip on the cpu to be totally bent out of its socket. The pinball worked just the same as now, but I could not start the code update procedure. By fixing it back into place I could update the code but the sw issue remained there. So I dont think its related.

Thanks for any hint!!!
Cheers from Italy

So, after some more troubleshooting, I think I can rule out a cpu bord problem.
I disconnected the opto amplifier board under pf and the problem has disappeared.
I’ve read that this little board is quite prone to failure.

I’ve tried to reflow solder on every component but no success.

Since its a super cheap piece I’ll try to replace it hoping it will solve the issue.
Fingers crossed!

So, the opto amplifier board was indeed the cause of my problems. Switched it for a new one and the issue has disappeared.

Thought this might be helpful for other people to know