The opto is a digital control, on/off as far as the pinball machine is concerned. There is no analog sensitivity to the flipper buttons that will send a varying voltage to your flipper coils.
Hi as I stated earlier, I understand a single opto is a digital control and an opto pair is simply a pair of digital controls. At no point have I mentioned the word analog, I KNOW it is not analog. I am a partially qualified electronics engineer, and I could write a simple circuit using early '80s integrated circuits that could measure the time difference between the two opto's regisitering an input. I could then write another simple circuit to use the output of the first to drive the coil at one of two different speeds using technology of the same era. As this is an early '90s machine the technology definitely exists. One of the first things an electronics engineer is taught about designing circuits is to reduce manufacturing costs by not using redundant components or materials. The opto pair is actually just 2 single optos mounted side by side, what you describe above will work with just one. This is very simple technology and the designers of the machine would have been acutely aware of this. I would be very surprised if they included a redundant component. (or a backup in case the first failed, it's not a plane if the primary fails and there is no secondary it's not going to kill people!). I'm prepared to accept that the machine doesn't have two flipper speeds but it makes no sense as to why the opto boards were designed the way the were. If I can design the circuit then the designers of this machine certainly could. Can anyone explain the redundancy of this flipper board? If this could be explained or proven that it is not redundant for a reason I am overlooking, I would appreciate it!
Incidentally for people who have this machine have a look at the the reel it has black plastic tabs that extend off it. It has 5 little tabs and one big tab close to one of the small tabs. Now if you lift your playfield out on it's runners look underneath the reel there is a metal bracket underneath it with 2 little U shaped pieces of (probably black) plastic. These are two more optos using exactly the same technology as what I described above. As the reel rotates a tab will first cut one opto and then the other for a brief moment both will be cut. Shortly after the first one is no longer cut but the second is still cut a little while longer. The reason for the one big tab is a "point of reference" both optos will be cut considerably longer with the big tab than the small tabs. This combined with the machines programming knowing the number of big and small tabs is so the machine knows exactly what position the reel is in, with reference to the 3 holes for the balls. So the designers clearly know about this technology as they are already using the exact same technology for a different purpose.
I think I will just go see the service agent again (might cost me but) he is a qualified electronics engineer and has worked (for around 2 decades) for the only company in my country that has imported pinball machines for the last 25 years or so into my region.
Thanks so much for everyones suggestions and ideas, I have enjoyed the exchange of ideas even if it didn't result in a solution.
Thanks again I will let you know what the agent says!