On my Riverboat Gambler (system 11c), switch column 7 is out: all eight drop targets do not register in Test Mode or gameplay. With connectors 1J8 and 1J10 removed the Switch Error message still shows at power up. The transistor (2N5550) for this column is R42, 1J8-8, green-violet wire. It tests good, same reading as all other 2N5550's with DMM. Logic probe shows "pulse" at U40 pin 12 (from Q42), same as others on that side.
I'm leaning toward the U40 (74LS244) or the U38 PIA (6821) as the culprit, but before I go ripping perfectly good components off this board, is there a way to test U40 and/or U38? Or should I look and test elsewhere?
Thanks in advance,