Updated 11/6/2019:
Today I attempted to troubleshoot and program my TPC-400 that I have owned for years. It last worked in 2016 when I tore down Panhandle 1.0. But yesterday and today - no soap. I finally removed and replaced it with a Legacy Powermaster (6-37146). As you can see in the photo below, we are now running on all 8 cylinders (Power Districts).
I am haunted by the thought that I was doing something wrong. This TPC exhibited the same behavior as the one I acquired and later returned. And that one is now functioning. I must have done something wrong, but for the life of me, I can't figure out what.
In any case, I have replaced older technology with the latest version. So on we go.
More when I know it.
George