To JGL: Thanks and answers:
1. Is the high voltage reading is simply a 'no-load' condition? Placing big resistors to draw almost 2 amps before train is started does reduce the voltage drop; not quite done testing that, but you have nailed part of the problem with stable voltage.
2. Yes I have ERR electronics inside the pre war locomotive to run it with TMCC. There are 3 of the motors involved, 2 on one TMCC board and one on a second board to run as a lashup.
3. Do you only have the single pre war locomotive that is a problem, or are you running several that would need a 'fix'? Yes in the sense there are 3 of the same motor involved in this one train. Only ONE train, though. Pride Lines COD A and 2 B's.
4. Are you running the pre war locomotive on the same track/power block with any other engines with modern electronics in them at any time? For any mainline operation, the answer is never; this is a long distance passenger train that will run from Chicago terminal to staging yard, and no need to run any other loco of any sort in the same block for center rail power. So whatever higher voltage I use with the COD train is only needed when it's on mainline. It can leave common areas where 18v is used, like terminal and staging, on 18v because speed is slow in all those places. For one grade situation, if needed we'll decide that a helper is needed and add a concealable coupler to obs car. A LionChief loco would serve nicely for that duty :-) Whole layout has common outside rails as a single entity; no breaks on common rail side of circuit anywhere on layout. Each block has paired + and common with circuit protection, but all common returns are bussed together at the phased-together power sources and united by the common rail as well.
5. Re: Arduino control of relays and diode drops: still very interesting, and I'm sure the learning curve would not be too steep. Just a matter of devoting the time to learn the tool, and then apply it to this case. Let me finish with the testing of the system with the 1.5-2 amp baseline load before I ask you to work out any Arduino details for my situation.
To GGG: Thanks---the MTH power idea is interesting. Would be a higher cost option since I would have to change out 3 motor units. Something to not forget if the overall solution remains elusive. If done, would be a fine permanent solution!
Don
