This thread is due for an update.
I took John up on his offer and paid him a visit. After exhaustive testing, we verified that I have a bad cable, AND that BOTH AIUs have issues. We also concluded that the failure mode was different for each one. No wonder I could not get anywhere!
Since published documentation on AIUs is sparse (understatement!), I contacted MTH Service through their website. Eventually I reached a MTH service tech who could guide me through the troubleshooting process. So with John telling me what to look for, and me reporting the symptoms to MTH, I was able to identify several bad/blown chips on the circuit boards. Unfortunately, I now have more experiece than I really ever wanted when it comes to replacing DIP chips! A big thank you to GRJ for helping identify and souce the necessary chips. So now I had 2 AIUs that could properly daisy chain.
I picked up a third AIU at the Fall York meet and added that to the mix while I was waiting for some parts to show up. With the parts installed, the 3 AIUs properly daisey chained. But now the relays would not fire correctly. The MTH people identified this as a software bug that is specific to RevL TIUs. The MTH people were able to provide me with the proper updates, which I installed. So at this point, I now have 3 properly functioning AIUs, and 2 updated Rev L TIUs.
The last piece of the puzzle is that the third AIU is located some distance from the the first 2 AIUs. I'm waiting on a long cable (ordered). With any luck, all will work as advertised and I can put this issue behind me.
So a big "THANK YOU!" to the folks at MTH and also GRJ for helping me through this mess. I appreciate it!
Chris
LVHR
