Have MTH F3 basic sound-horn system and basic coupler system (magnetic tack)- sound sticks and won't shut off -would like to swap out the entire system and move the shells

Why not just remove the horn board and replace it with any of a number of alternatives?  The ERR RailSounds Commander comes to mind.

Thanks to Gunrunner John and uberstation meister for the quick responses. My transformer is a MTH Z-4000- runs everything else just fine.  An MTH certified tech back in New Jersey said to look for a pinched wire with the lid off - did so and there are none. I live in Salt Lake City.

ERR used to be sold briefly  @ a hobby shop here many years ago- but no more.  The "genius" electronic  guys moved on- would like to learn more about where to get the right stuff for the upgrade and a  brief explanation of how to proceed ( a picture/diagram/photo of the swap is worth a thousand words)...

Thanks guy's !

For conventional operation, the ERR installation is quite simple.  You just need the speaker and power connections.  If you want the sounds to continue over direction changes and track power interruptions, I suggest adding a battery.  Naturally, I'd recommend my YLB - RailSounds Battery Replacement (RS-Lite) product, it's a once and done battery installation.

Here's the wiring diagram from the instruction sheet for a conventional installation, really simple.  FWIW, the battery is optional, like I said, it keeps the sounds going on direction changes and power interruptions.

Thanks Gunrunner for the quick response with the diagram. I like simple to understand in my (76) year old age.

Imagine how I feel my old age!

The pinch may not be a pinch, but can be any other source of DC on the chassis.  Motors and motor leads (where soldered) and also split insulation can be the cause.  I assume this is a DCRU with horn board.  You can just disconnect the horn board, or speaker.  But I still would want to find the source of the issue.

Also dirty wheels and corroding pickups can cause issues too.  G

Hi GGG- Thanks on the heads up. I'll take another look under the hood-see if I missed something. Still would like to find a reasonable MTH F-3/F-7 dual motor powered chassis-maybe with bad shells so I could pickup all the other goodies- electric couplers Proto sound etc. My main criteria would reasonable price & working condition...