A bad transistor.

So if you were to ground the metal tab of Q-14 with a jumper connected to the ground braid, does the flashers light now?

No big.

Maybe?

This is a correct part.

???

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I would use a logic probe or DMM and test the output of U-17 pin 8. In attract mode pin 8 should be a low/0.8 volts.

This seem normal, now check SR5 pin 9 in attract mode. Should be 0.0 volts.

Correct the white dot is pin #1.

This would indicate that Q-10 is still good. So this just leaves Q-14. Now the question remains why Q-14 went bad? Are you running standard #89 bulbs or leds? After replacing Q-14 I think I would do a current test manually on this circuit before turning on Q-14. This can be done by using your DMM in series with this circuit. Set DMM to DC current, move red lead connection to correct spot, hook black lead under ground braid, turn on game, then touch red lead to Q-14 metal tab. Read meter and disconnect red lead. What do you get?

That seems fine too. Maybe you just got a bad TIP 102. It happens.

The wire solder tabs can sometimes spin around and touch each other, this will be a short circuit. If this happens it will pop the transistor the first time it turns on. You may have inadvertently spun the wire tabs apart when you changed the bulb removing the short, but the TIP was already damaged. This is something I always check when I bring home a new game for the first time.

Is there any alkaline damage to CPU board?

Well as SRC-6 goes, that was a very good temporary repair. I don't think that this is the cause of your flasher issue, but you never know. Either you have a part that is randomly acting up (U-17) which is smoking the driver transistor or maybe this Hack is causing erratic switch closures causing the driver transistor to lock on. Replacing SRC-6 with a non capacitor resistor pack is well documented on System 11s. Try that with a new TIP102 and retest.

Since you know SRC-6 is bad, then replacing this first might be the way to go for now. I would purchase some AND gates just to have on hand anyway. Also some chip sockets too.

There are many TTL logic gates used on the CPU board. U-17 in the circuit you are working on is an AND gate. It has a part # 7408 under the label.

https://www.marcospecialties.com/pinball-parts/7408

https://www.greatplainselectronics.com/proddetail.asp?prod=7408

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The 4 flashers in the backbox, alternate back and forth in pairs during the game and at the end of the game.

You either have alkaline damage or you have bad game rom sockets. If your board looks good maybe you should change sockets if your able.

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I have seen this before, but not very common. The flashers could also be part of the erratic behavior.

I understand that something on the play field could be miss wired/shorted and be causing damage to Q-14, but this can't set off random sounds. Now if U-10 was to be acting up it could set off some coils( solenoids 9-16) and some sounds. But bad sockets on the CPU chips could cause this also. U-10 isn't socketed from the factory so you can't swap in a different one for easy testing. Williams did use cheap sockets that are @ 35 years old now. I can't tell you which is the best direction to go, from my couch. But you know what your options are.

It has only a 5 ma current limit.

https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/DM7408.pdf

This one has 16 ma current limit.

I'm not sure what you mean by "The original setup" ? None of the flashers should glow dim. And they should fire very bright during solenoid test.

When you restore the missing bulb sockets I recomend you use heat shrink on both the sockets and the switch stacks next to them. You don't want 30 volts touching the switches which are 5 volts.