This column is mostly the upper targets, and none of them work. When I pull connector 1J8 and measure voltage at the pin, I get only 3 volts. All of the other pins are at 4.8V, so something is obviously wrong with the board. Do I replace the transistor or something else?

They are in the same column, which is Column 7. Collector of Q42 is at 3V relative to the Emitter (GND). The Base is also at 3V versus less than .2V for all of the column transistors, which makes me wonder if U40 could be bad.

The board was professionally repaired and tested by CoinOp Cauldron, and it worked fine for a few months.

I will do that. I have spare transistors and 74LS244 chips. I just wanted to get some opinions before tearing into it.

Dude, re-read my first post. I unplugged the connector. Playfield is not connected.

I'm going to go replace Q42 and will report back.

I thought I had some, but apparently not. I wish the rat shack down the street was still open. I'm going to look at some of the other miscellaneous boards I have laying around to see if I can steal one from somewhere. I parted out a GL a while back and have a lot of System 11 stuff from that.

Replaced the transistor, powered it up and the switches worked, but they were activating the whole row. Checked the transistor and had very low resistance between both the base and emitter and the base and collector. Should be around 6-7k from what I could tell on the other ones. So I changed the transistor again. I got almost a full game in before the same thing happened. Something is causing that transistor to pop. Could it be U40???

Saw this in the System 11 Club thread. I guess I need to go through all the wiring and look for shorts.

Quoted from Tomass:
Ok, I see why I ended up with 2n5550's and not 2n3904's. The 11c board has the 2n5550 transistor on q42-q49 but the 11a has the 2n3904 transistor in that same spot. Seems like it is the same but higher rated voltage, but that is only from reading other posts. I would think it will work since it is in the 11c board and perhaps even an upgrade? Am I wrong?
Thanks for any input

Exactly. It's functionally the same transistor, but it doesn't blow up instantly if a higher-voltage wire accidentally touches its circuit due to a fault on the playfield. Just a little more robust, and a slight bit of insurance against ignorant folk working on the game with the power on.

EOS for the upper flippers? They look fine. I checked the entire length of the wire for column 7 and can't find any evidence of shorting.

My problem is with Column 7 though, not Row 7. That's the upper pf "TOMCAT" switches, Line of Death, and Top Left loop. Nowhere near the lower right flipper.

Green/Violet. Q42 is blowing. Column 7 is on pin 8 because of the key.

Still have this problem. Grumpy, are you saying that something is shorting to white/violet, which is wiping out Column 7 whenever the Line of Death switch is active? Why wouldn't this affect any of the other columns?

I disconnected white/violet from both flippers and got several games in, but alas, Q42 eventually blew.