We are working on a Tommy that has a most peculiar problem.

Sometimes when you turn the machine on, none of the coils will fire. Other times, they will.
When the coils will not work, going into the diagnostics and running a test will sometimes magically fix the issue.
Once the coils are working, they seems to work fine until the game is turned off.
I have run a full switch test (including the trough several times) and cannot find any problems.
The relay has also been replaced, as well as its transistor.
I should note that when the coils will not fire, the corresponding flasher will fire (hence the relay replacement).

Is it possible this is a chip related issue? I was thinking about trying the logic probe up the chain and see what I could find, not that I really know how to use a logic probe

Thanks!
-Matt