I'm not sure how much I'm helping but thanks
The switching is done by the relay.
So back to the start, Q31 (Double Score Flashers) & Q33 (Left Upper PF 'JO' Flashers) are still causing the transistors to die, also taking out fuse F2C?
Is this still the case?
I'm stumped at why the transistors are failing/dying and not protected by the fuse?
The following is with the game off.
J11 pin 1 on the Aux Board is the power for Solenoids 1 to 8 on the C side of the relay, but there aren't any solenoids on the 'C' side, they are all flashers, the 'A' side is for the switched solenoids.
The flash bulbs are easy to get to, so I'd start by removing the 2 in question. Also look at the housing of the bulb, and test the diodes at the base. Shorted diodes might cause the problems you are having. Visually look around for solder tabs touching each other, the odd strand of wire not soldered and touching something else and the like.
It must suck swapping out transistors.
You could remove the bulbs which in turn stops the circuit and try again? ........but first try, with the bulbs removed, and J11 removed from the Aux Board, use your meter and check for where the shorts to ground are? This is me assuming that it is a short to ground that is causing the problems.
So with the transistors changed and J11 not connected, your meter set to continuity, put either probe on J11 header Pin 1 (Q33) and the other probe to any part of the ground plane and you shouldn't hear a sound/show maximum resistance, so in other words no short and circuit is good. If you hear a sound then you've found a problem, but you have already tested the Aux Board without J11 connected and all was ok.
J11 header Pin 6 (Q31) and the other probe to any part of the ground plane and you shouldn't hear a sound/show maximum resistance, so in other words no short and circuit is good.
also touching the metal tab of the transistor with either probe and touching ground with the other probe it should be the same, if you hear a sound/zero resistance then the transistor is shorted internally, you can try this when you know a transistor has died. The alternative is a transistor going open but it won't take out a fuse as there isn't a circuit.
with J11 not connected now do the same but put the probe on the mating IDC (Insulation Displacement Connector) pin and the other probe to ground and hopefully through some testing you will hear your meter and will be narrowing down to the culprits
also all the connections from the playfield use the interconnect board and the flashlamps use J4, check resistors R1 & R5.
I don't have a System 11 pin but am wondering if with the bulb removed and dead transistors in place/or not, if in lamp test via diagnostics if it might display an error in more detail, like directly?
anyone reading this, if you have any ideas please jump in as all the more help would assist.