Hey guys, a while back I received an error about Opto Switch 82 being stuck open. I've been playing it for a while but now trying to fix it. I've done some basic troubleshooting, all optos transmitters have 1.39v and all receivers have 13.5v when "open". I switched a couple transmitters/receivers and still get the message. Even if I directly jumper a piece of wire the back of receiver opto on 82 it doesn't do anything so I'm pretty sure it's a circuit issue (81 and 83 both close when I jumper them). Tonight I socketed the LM339's on the accelerator board and installed new LM339's but still now luck (got the idea for that here - http://techniek.flipperwinkel.nl/wpc/index3.htm#opto). Also swapped out the U20 chip on the MPU just in case but still no dice. Not really sure what I should check next. Any ideas?