Assume you mean the VCA TO MONITOR?
The card in question is the 82E21 in the centre section.
As it switch lights up, at least everything works up until the T4 NAND gate.
Check pin 21 of the 82E21 card, and ensure the status voltage changes when switched.
I would be looking straight at the TR7 BC212. These blow out regularly, and are all over the logic cards.
Anthony.