First off, I wish a Happy & Healthy New Year to all,

I've been diagnosing a lamp matrix row failure, row 8 lights are out. My diagnosis has led to the failure being on the driver board not the playfield.
I purchased a Logic Probe & I have to say this thing is really cool. So I've been testing the failed circuit comparing results to a working circuit & found many differences with most of the components. The difference starts at IC12 output, so I'm assuming the other components in the failing circuit are getting different results from the working circuit because IC12 seems to be failing. Am I correct in this analysis? I realize there could be other failing components after IC12, I did already replace Q59 2N6122 Transistor because it was shorted out but that didn't correct the problem. My real question is, could a failing component after IC12 in that circuit cause IC12 to read bad? Or should I start with replacing IC12 & work from there?

Thanks for your reply Tuukka,

If I remember correctly IC12 pin 2 was high, but I will have to confirm, also I have checked that the playfield is good. If i pull the connector & jump a any working pin to row 8 on the connector, those lights works fine. So the playfield wouldn't be an issue, correct? I will recheck R130, Q58, Q59.

OK, thanks, I will check those.

I just checked IC12 pin 2 & it's low, so I checked S7 compared to S8 & this is what I got.

S7 = C Low B Low & E Low
S8 = C Low B Low & E Pulsing Low

Then compared R129 to R138.

R129 = High & Low
R138 = High & Pulsing Low

Bump

Not sure this is relevant to my issue.

Hats off to Tuukka, it was the 2N5060 SCR @ S7. All good now.
Thank you Tuukka