Update: Had a friend look at the board. He replaced (2) 2N6427's in the lower right he said were the wrong type.
Also pulled/installed all (8) TIP42C's ..Said the ones he pulled were not the right ones. I am trying to find the baggie with them in it so I can post what they were. He touched up some solder and tested runs with a DVM.
When I put it back in the pin, it was exactly the same way as I described before.
I snipped out IC12 (acid corrosion) and replaced with a 14 Pin socket and a N7406 IC.
Try it back in the pin. Same problem..
Swapped in a known good driver board from my Pharaoh. All worked perfectly.
Column 4 lamps still out with the bad board in.
Question: Even though IC12 was a mess (see pics) , does it control IC13 or go thru IC13 which is the 7408 for Lamp Driver Columns 1-4 according to a schematic I downloaded in this thread?
IC13 looks fine but is there a way to test before snipping out more IC's?
Can I test this with a logic probe or DVM easily enough? I'm smart enough to follow step by step instructions but I am still a newbie at reading/understanding electronic schematics.
Thanks if you can assist!