So I'm helping a friend troubleshoot a lock-on coil issue with a Banzai Run (System 11). After much troubleshooting, the issue stemmed back to a bad PIA, which had taken out a downstream zener diode and several other components with the lock-on. While in there doing work, he decided to replace the cluster of 6 pairs of driver and pre-driver transistors to improve the longevity of the board. Upon powering up the board, both slings locked on (a new problem). After some troubleshooting, it was determined that six 2N4401 (NPN) pre-drivers were inadvertently replaced with 2N5401 (PNP) pre-drivers.

Any idea what the damage might be from this (I'm thinking that the sling's driver/predriver at a minimum, if not the TIP36/diodes on the aux driver board).

What's I'm trying to understand is why all 6 solenoids didn't lock on as a result of this mistake? Can anyone with some more technical knowledge explain this? I would think that a PNP vs. NPN mistake on a 25V or 50V solenoid should be immediate for all the affected components. Or is it possible that some could have ended up in a "doesn't work at all" state instead of a "locked on" state?