Problem: I discovered that my clock didn't work properly on my newly
purchased Twilight Zone.
After examination I found that the optocouplers were intermittent. I assume
that the heat from the bulbs wired to GI caused the IR sensors to misalign
Fix: Replace the optos one by one with cash or for 0$:
Grab a pair of plyers and grab hold of the opto black cover--It's the black
plastic thing that looks like a big 'C'. Gently remove the cover by slowly
moving the cover back and forth. Pull up gently and the optos will be seen
pointing at each other. One is a transmitter and the other is a receiver.
Realign the optos carefully with the test utilities so the beam becomes
non-intermittent. Leave the cover of the opto off. I personally think the
the clock looks better with the opto covers off.
This fix also worked on my intermittent TL flipper.