MTH Z Controller puzzle - Question

A couple of thoughts.  It's likely your meter is not a True RMS voltage meter.  Since you didn't mention it, I'm also guessing you're not measuring the controller output voltage with any significant electrical load on it, other than a high impedance meter.  Some sort of load (like an incandescent bulb in parallel with the meter) will make the measured AC voltage out of the controller read higher on your meter.

A word of caution with this 24V brick is that it exceeds the recommended 19 volts Lionel recommends for LionChief and it's other command controlled locomotives.

With these considerations in mind, this Topic may help you understand these mysteries a bit better.

Chopped wave transformers: How much voltage is really going to your engines electronics?

Thanks Steve for your response.

I did have an engine moving slowly on the track while I took readings. 

What I have not seen before is this MTH set up where they used a Z controller 750 paired with a 24 VOLT brick.  This Z controller does not behave like the two I already have.  It only puts out about half the voltage (at full throttle)  when paired with one of my newer MTH bricks.  When the 24 VOLT brick is paired with it's mate,  they run a basic train fine (no electronics).  I was wondering if the controller was somehow "governed" inside to put out only the 12.5 volts regardless of the 24 VOLT brick.   

Any idea why MTH produced this arrangement?

As you mentioned, 24 VOLTS is too much voltage for our O guage  trains.

Thanks Dave

It sounds like your controller is suspect, especially because you say that it doesn't behave like the others you have.  If you put your meter on the raw output from the brick, what do you get?  What happens if you plug the 24V brick into one of your other controllers??

It's true that Lionel warns against putting more than 19V on the rails for Legacy and LionChief, and I'm careful not to push it.  But I will call them out here for a shortsighted design decision.  Many existing prewar transformers put out 24V, as did the Right-of-Way transformer circa 1990.  Some conventional locos need that much!  The venerable ZW puts out 20V, and the Z-4000 21-22V at open circuit.   So Lionel imposed this arbitrary lower ceiling sometime in the last 20 years, giving us one more thing to worry about.

It frustrates me, because using 24V motors combined with a higher track voltage would have yielded a small performance improvement and lower current draw, relative to the 12-15V can motors found in premium steam since the mid-1990s.

Same brick but differing Voltage looks a little sloppy on MTH part.

set your controller at halfway pull the knob off and push back on at off position than crank it up all the way and see what your reading is than

Thanks for the responses Gents.

As requested, the MTH 24 VOLT brick puts out 24.7 V.

When it's mate, the Z750 controller is hooked up to the brick, it will only put out 12.5 V.

Take that same controller hooked up separately to my 2 MTH bricks putting out 18 V and it will only deliver 9V.

So yes Ted, it does seem that the Z750 is faulty.

I have done a lot of searching, finding many incidents of the Z Controller putting out the full 18V with no control.

But I have not found any incidents where the controller is "halved" in it's output as mine is.  Half of 18V at 9V and half of 24.7 V at 12.5V.

I am not likely to use this brick but I would like to save the Controller.

Anyone have any ideas on which component may be at fault in the Z750 Controller?

Again, Thanks for the responses.

Dave

You can buy the complete circuit board from MTH Parts and Sales for less than a new controller.  With an AC voltmeter, you should be measuring close to the brick’s output at full throttle.  No true RMS meter needed.

Why did MTH make the same model transformer at to differing voltages ?

Early and late.  Who knows why.  But MTH engines have no issue with higher voltages.  G

@GGG posted:

Early and late.  Who knows why.  But MTH engines have no issue with higher voltages.  G

Well I get mix messages about voltage and MTH electronics. I am cautioned often about high trac voltage and PS 1/2 boards. Was this not the case for PS 1 boards and the PS 2 5V failures ?  Or was there operator’s error involved ?

on a side bar I would like to ask some additional questions about MTH boards my I contact you on private message

thanks

Yes. G