Finally did diagnose the problem as a 2.5 volt drop under load at the T-injector. With the output on the bench showing barely 11v under load this brought the voltage down to the bottom end of what the ARR preamp needs to function. I suspect that under load at the end of 60' of coax it was even lower than 11v. Jay at ARR was very helpful in working with me to get to the bottom of the mystery as I had the same problem with two different vintage Mirage T-injectors and both worked fine with Mirage and Icom preamps, so it was quite a mystery. We determined that if you eliminate the 10ohm resister off the injector pwr switch and replace it with a jumper the problem is solved. Of course I could have used a separate line to remotely power the ARR preamps but that was going to be very difficult at my QTH. Problem it looks like is solved. And thanks to everyone for your useful suggestions and questions that led to solving the mystery.
73 Rick, W2JAZ