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Had a really strange one yesterday. I have a test track in my workshop, just a 40" piece of tubular track hooked up to a Z-750. I wanted to test the basic functioning of a newly arrived MTH Traxx locomotive, so I plugged a TIU into it and tested the unit. Things seemed to be going fine when, for some reason, I took a track voltage reading with the remote and it read 32 volts! That's really weird, since the Z-750 will only put out 16, max. So I put a voltmeter on it. Sure enough, the meter was giving me 0-32 volts at the track. Took the locomotive off the test track, still 32 volts. Disconnected the TIU, checked the output on the transformer - 16 volts, just like always. The TIU was connected correctly to the track through the Fixed-1 channel and everything worked normally when I was testing the locomotive. I've never seen anything like this with the TIU hooked up to a Z-4000 or an old KW. The Z-750 is the later version, after MTH modified it to work properly with Proto-1.

 

What's going on here? Is this some anomaly related to the zero or light load, that would go away if I was actually drawing any significant current? I couldn't actually move the unit more than a few inches because it was just a piece of straight track - I had to take down my test loop when I finished the benchwork on my layout and I don't  have track on the layout yet, so I can't do a full-operation test.

 

Can anybody explain this? 

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Perhaps some sort of sine-wave oddity causing the meter to read more than the engine is actually getting?

 

There was a discussion over a Lionel video discussing transformers, and there was mention of smoke units performing better on a CW-80 than a postwar transformer because the chopped sinewave delivers a higher voltage that is seen by anything fed through a capacitor. Or something to that effect. Perhaps related?

 

---PCJ

Did you have the Z750's controller hooked up, or did you plug the brick directly into the TIU??  TIU Fxd 1 channel, I assume??

 

Analog or digital doesn't matter, but volt meters may be designed to read voltages differently, e.g. peak, RMS, average.   Each of those meters will also be designed for a specific wave shape. 

Originally Posted by Gary:

Thanks. I always wondered what that TIU/barrel jack adapter was good for. As far as the thread goes, it confirms my observation about the voltage readout on the PS3 locomotive, but but it peters out without a firm explanation. There is the suggestion that the meters are measuring peak to peak. Also, at least one of the guys who posted in that thread checked his track voltage with a regular meter and got a normal reading. My meter agrees with the locomotive. I might try another meter (I have at least three) and/or a PS2 locomotive on the same setup, just to see what happens. 

I just checked with Barry's book and the real world - plugging a Z750 brick into the AUX input lights up the TIU but does not provide any track power. I'm still wondering why I get those strange voltage readings. That does remind me, though - I'm moving from a single test loop to a multi-track layout, so I will have to make provision to power the AUX input so the TIU will work regardless of whether I apply power to Fixed Input 1. 

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