MTH Z-750 woes. Help appreciated.

I had this same problem last year with my Z controller for my Z1000.

It was cheaper to buy a new one than try to have mine repaired.

I also had the same issue with a z750 controller. The controller can be purchased separately. The new controller I got had a 6 amp rating.

Thanks for the advice, gentlemen. Sounds as if a new controller is the best way to go.

Better than even odds that it's the triac semiconductor component that shorted out.  While it's a $1 component, it's difficult to access/replace and requires soldering.  Given labor costs, I too believe it might well be less expensive to replace the controller than to pay someone to repair it. 

Obviously time is of the essence since this is a holiday setup.  But if at some point in time you want to roll the dice on a DIY repair, ask again and I'll post some photos and instructions on exactly how to replace the triac in a Z-750 controller.

Thanks, Stan. Fortunately, I have another that I am taking to him on Friday so there is no major time cocern. I noticed that the replacement is six amps like Alextwister stated above so I assume that means it has a higher rating/tolerance and is less likely to blow. I don't know how many amps the blown one is but I am guessing it's fewer amps. If the voltage is constant coming from the brick then why does it suddenly trip the triac semiconductor? And do the later controllers have a heavier load? If someone were to open the throttle too high and too fast (like a young child) does that risk the failure? Just wondering.

The Z-750 transformer puts out a max of 21 volts.   Way too much for our trains.   No way it should be turned up max.

The original z750 transformer controller was rated at 4 amps. The replacement  controller is rated at 6 amps which is what the z1000 controller is rated. I tried to get an electrical schematic for the z750 but MTH never got back to me.

Check out this thread:

https://ogrforum.com/...stant-18-volt-output

Similar problem of full-voltage to track irrespective of controller throttle setting.  From what I can tell, MTH consolidated the 50W, 75W and 100W controllers into a single model.  4A x 18V is about 75 Watts (Z-750), 6A x 18V is about 100 Watts (Z-1000), etc..  As shown in the other thread, replacing the likely-suspect component(s) is a roll-your-dice proposition which didn't win in that case.  It's just that the components are $1 or so, so if you have the time and interest it can be a rewarding experience to bring something back to life.

I don't think how your son turned the throttle blew the controller.  Consider that every time you press the DIRECTION button, the track voltage instantly drops to 0, and then instantly jumps back up to whatever track voltage as you release the DIR button.  That kind of transition is surely faster than how fast a kid can turn a knob!

Great information and reference. Thanks. It will be a few days before I get the thing and can open it to make a decision as to how I will proceed.

Check the top of the brick of the z-750.  Puts out 21 volts not 18.