Hi all and happy new year !
My Williams system 3 Disco Fever is driving me mad.
As soon as drop target 'E' or 'R' goes down other inputs corresponding to the same column stop working.
Even when drop target E or R are not down the inputs of the same column are not very responsive.
They need to be triggered several time to report 'closed' when in test mode. Other inputs from other columns / lines are responsive as normal.
I checked all diodes and connections for shorts or open circuit (from 2J2 and 2J3), I even checked for ground fault. Nothing found wrong.
I tested the switch matrix from 2J2 and 2J3 using jumpers with diodes (to simulate multiple inputs closed at the same time) and every thing report perfect and in a responsive manner. What can I check next? Any idea what the issue could be? I'm lost :-s
Thanks for your suggestions.

schematic (resized).jpg

THanks Slochar,

I have ordered new connectors for 2J2 and 2J3 already so I will see when I get them but I don't think it is the issue as I tried hooking up the specific column / row directly and it behaves the same. I read somewhere that it could be related to issues with IC15 or IC16. I have also ordered new ICs and supports.

I have planned to 1st replace the connectors and then do some more testing (disconnecting each contact one after the other until I find something).
Will see...I keep you guys posted.