Quoted from Xtraball:The tech thinks it might just be a bad led.
It could be a bad connection to the current limiting that powers the LED, this resistor is right next to the capacitor and dielectric that leaks out of capacitors is corrosive. Personally, I would not have returned a board with a non-working LED.
Quoted from Xtraball:I thought maybe another component somewhere was heating up?
Could be...perhaps U2 (LM336), but its also very unlikely as these are quad comparitors and a heat issue would likely effect more than one of them; could also be R25 on the 16 opto board if you are pulling excessive current as resistors increase in resistance as they get hot, this is also an unlikely scenario.
Quoted from Xtraball:After about an hour of frustration I began mounting it back into position and IT STARTS WORKING! I pulled, tugged, bent wires and pounded on the playfield and couldn’t get to NOT WORK! So I put the balls into the game and stared at a perfect switch edges display...and 5 seconds later the switch went open again.
You got to love problems like this...so frustrating 
This is likely going to be a wire connection or cracked solder joint.
Have you checked the opto connector for the VUK? This is a 12-pin Molex type connector, looks like this:
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Are you positive you are working on the correct optos?
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Next time it stops working, remove all of the balls, lift the playfield, and measure the voltage on both of your optos for that switch, one lead on each wire ... E and C on the Photo Transistor board, A and K on the LED board; record these 2 measurements and let me know what you have. Do this while in switch test so that if one of them changes when making the measurement you can here the switch change states.
Elizabethtown, KY
