Doctor Who, problems with optos

Hi all!

I'm going crazy over my Doctor Who mini-playfield. I'm having problems with the
optos, so I changed them all in one go. Then some of them worked, some didn't. So
looked the small boards over, reconnected, and now some other than before doesn't
work. Seems sporadic. I changed to 'high-output' IR LEDs, now NONE work.

So, I'm about to change the IR LEDs once again, to try my luck with some others.
I am paying attention to what nM I'm using etc.

I find it very hard to find infomation about this. I know I could just order IR LEDs and
receivers from a pinball shop, or even just buy the repro boards...but have this idea tha maybe these transmitters/receivers shouldn't be that expensive.

I do find it strange that the numbers on the two boards doesn't add up - for
example Q4 will line up with LED2 when the boards are installed on the plastic
housing. Can anyone confirm this?

Thanks!

Nicholas