There is a thread on this forum from October 6, 2012 that has some very interesting technical details on the TAT IV throttle. A user who signed himself "RBC" and used the handle "bullchitbids" (use this as a search term in 'community search' to help finding a post from that far back) noted that he then had a copy of Dennis Blunt's Transitrol build manual. (And demonstrated that he had the knowledge to understand what its details called for.) It is possible that Kalmbach reprinted the then-current diagram in one of the Brandywine Traction Co. articles in the mid-70s, and that would give you a leg up on values and component types that you could at least re-engineer.
Since the PM function no longer works here, you'd have to ask if anyone knows him, and can get him to post again in this thread if he is still 'with us.'
Hello,
I have all of the original articles from Model Railroader for the TAT III and TAT IV throttle and I'm in the process of working out the component substitutions that would allow me to build the TAT IV using modern components.
I was wondering if anyone has a copy of the build manual that was put out by Denis Blunt when he was running Transitrol please? If you have it and can either copy it or are prepared to sell it to me please get in touch. Please however bear in mind that I'm in the UK and I'm unsure how much the postage might be to send something like that.
Best Regards,
Jules (TriangTrain)