Hi! Took awhile to read all of this thread
I have a D&D almost working, just a few things that I have questions about.

During gameplay, all I hear are the gongs and no music or laughing by the witch or the dragon. Not sure why, might be in the sounds testing, but very stumped because some of the sound works.

When the back pop bumper triggers, the right one triggers as well, but when I try to activate the right one, nothing happens. Is there messed up wiring somewhere?

Other question is that when I have 3 balls installed in the game, its says ball missing but adding a 4th ball starts the game. The trough opto board I got had 4 emitters but only 3 receivers so I added another receiver. Was this the play or what was I supposed to do instead? I was reading that 4 balls is the way but when I look elsewhere I see that 3 balls should only be installed.
Thanks for the help!

I tried reaching out to Great Lakes Electronics and they did not reply to any of my emails. I am a little nervous that they went out of business!

Hey pinballfan I got the trough opto boards a few days ago actually and I just saw your message haha it works wonderfully!

Now, the reason why I've come back to this thread, I'm having an issue though with my game though. When I lock a ball sometimes, and then the ball goes into the back left dragons lair switch, or just the ball goes to the left dragons lair switch in general, the right dragons lair coil will fire over and over but the left one won't fire. Why is this? When i turn the game off and turn it back on the left coil kicker fires to knock the ball back into play. Please help thank you!

It might because I have only 3 balls installed in my game....will check when I get home today. Problem only happens during multiball when I only have 1 ball locked.

---- EDIT...I think I might just extend the rubber so the ball doesnt go in that eject anymore. It only happens during 2 ball multiball and sometimes it kicks on the left and sometimes it kicks on the right, and I can't seem to duplicate the problem on a consistent basis. when I drain out of multiball it kicks the ball out. Could be PIA chip

https://www.ministryofpinball.com/en/trough-opto-receiver-board-bally-6803.html
https://www.ministryofpinball.com/en/trough%20opto%20transmitter%20board%20bally%206803.html

I will replace the cap on the switch when my order from Marco comes in next week. This game has always been an issue but its a keeper. Game was hallowed out when I got it. No boards, not even the transformer was in it, only thing that was there was the cab, the stripped playfield, and the fuse block on the left.
Sometimes I think this hobby is a money pit, but then I realize after my 10th game that its an INVESTMENT

awesome! they got my D&D working as well!

Someone said CPR is making a playfield for this game?? Can anyone confirm thanks