need to find out if the transistors are failing due to the cpu or the playfield.

have you tried powering up the game with J11 connector removed?
If the transistor fails with the plug removed the problem is on the board, I'd say unlikely but expect the unexpected. There'd have to be a short straight to ground.

what transistor are you using to replace the original TIP122's ? Ideally TIP102

It may be a faulty logic gate in U19 for Q31 and U20 for Q33?

F2C is for your low powered coils on the C side for solenoids 1-8 being

Jokerz (resized).png

so it makes sense F2C has gone open

yes if a diode shorts internally as opposed to going open, the current is going straight to ground and not through the coil winding.

unlikely the relay board is at fault, but with the board out you could check the associated diodes D45 for Q33 & D37 for Q31. As there isn't a circuit due to no plugs connected you can test the diodes in the board, no need to lift a leg.

My replies have been purely to looking at the schematics.

But no the voltages don't appear correct to me.

So testing voltages with only J8 a 9 pin plug connected?

J11 pin 1 is connected to fuse F2C (5A) then to the C side of the 25VDC relay, which goes via jumper W6 to the 25VDC supply, which derives from the 26VAC transformer windings 6 & 7, so 40VDC does seem too high which leads me to where/how are you getting the results, like what probe to where? Not doubting your testing procedure, just curious, maybe below will help?

you could try testing your transformer voltages at J8?
meter set for ACV
either probe on pins 1 or 2, and the other probe on either 3 or 4 should give you a reading of 26VAC (the + leg of C3 should give you a reading of 25VDC)
either probe on pins 6 or 7, and the other probe on either 8 or 9 should give you a reading of 48VAC (the + leg of C1 should give you a reading of 50VDC)

Aux Connections (resized).png

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.

There is a lamp circuit that likes to blow out in this game. There is two flashers on one circuit. In my dad's game the transistor was burnt when we got it and then it burned out a 2nd time. It seems like they forgot to use a current limiting resistor on the interconnect board and the flasher filament when cold exceeded the transistor limit for an extremely brief period of time. It was just a zero ohm jumper. I think we put in low ohm resistor there and upgraded the transistor from TIP122 to TIP102 and it hasn't blown again.

https://www.pinwiki.com/wiki/index.php/Williams_System_9_-_11#/media/File:System_11_Lamp_Board.JPG

Does your board have the resistors going to the flash lamp for the transistor that is failing? The one found in a Jokerz did not. I think we put in a low ohm(under 1?) 5w cement resistor in the circuit that blew out twice. I think it was one of the only circuits that had more flashers than the rest. Its possible that game wound up with the wrong interconnect board installed.

I had a bad batch of tip102,s a while back. Not sure why but they failed to a shorted state.

IDC = Insulation Displacement Connector

to check if the A/C relay is working put the game into solenoid test via the front door, solenoid 12 (Q8)

It sounds like you have a bad coil diode. When a coil activates it creates a magnetic field. When it deactivates that magnetic field travels backwards into the transistor causing it to short out. The diode is installed on the coil in order to collapse that magnetic field preventing that from occurring. If the diode shorts it causes the fuse to blow, if it goes open it causes the transistor to blow. What often happens is that a diode goes open causing a transistor to short, the shorted transistor causes the coil or flashers that it is controlling to lock on and overheat causing the fuse to blow as designed. An open diode does not always cause the transistor to blow immediately, but sometimes it does happen instantly. The only thing guaranteed is that it will eventually cause it to blow. The most important thing to understand is that a shorted diode will not always just short the transistor associated with that particular coil/flasher, it can short any transistor in that section of the board. This is commonly seen on Williams system 11 and Data East version 2 boards. An example is a Data East Simpsons that I repaired, it had an open diode on the left slingshot that kept blowing the transistors for the lower pop bumper and the backbox flashlamps. They were all located in the special solenoids section on the CPU. My point is do not stop at just the diodes of the affected coils, test and/or swap all the diodes related to that section. Also, just to clarify, 9 times out of 10 a transistor is going to short closed when it fails. They do occasionally fail open but very rarely do so. A diode is the exact opposite, it most often times fails open.