Dear DNA, I am not sure exactly which switch you are looking for a setting on. The title of your post says turbine comp't temperature setting, but then another part of the post lists 26BA-1, and lastly in your post it lists 26QA-1, so I'm a bit confused.
A device spec I have for a vintage 1985 Frame 5001P has the following settings, hopefully one of them is what you are really looking for. I do not have a listing for 26BA-1, seems like some sort of alarm setpoint.
26BT-1, turbine comp't high temp alarm 300 degf.
26BT-2, turbine comp't fan shutoff 95 degf.
26HT-1 Turbine comp't heater control 40degf.
Lastly 26QA-1 lube oil header temp high alarm 165 degf. which of course has nothing to do with the turbine comp't temperature.
I hope one of these is what you needed and it seems realistic for your machine.