Grab a jumper wire stripped at each end.
Connect one end to ground.
One at a time, touch the other end of the wire on the Anode leg of the Q7 and Q27 SCRs on the lamp driver board. If the respective lamps illuminate it says continuity from the SCR to the lamp sockets are good. No illumination means a connectivity issue.
The small SCR Anode leg is the lower right leg on the board - you will notice the right most column of SCRs have their legs marked.

Next, disconnect the jumper wire from ground and connect it to test point TP3 on the lamp driver board. One at a time, touch the other end of the wire on the Gate leg of the Q7 and Q27 SCRs. If the respective lamps illuminate the SCRs are good and the problem is likely upstream at the 4050 buffer chip. If the lamps do not illuminate the SCR is faulty.
Test point TP3 on the lamp driver board is there specifically to help test SCRs as a mechanism to manually switch them on.
The small SCR Gate leg is the upper middle leg on the board.

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