I have a friend that came to me with a used MTH engine with PS3 (30-20235-1) he bought at a flea market for $100. He said the guy put it on a track to test it, and when it started he acted surprised that it did (red flag to me that he expected it to fail). When he got it home and put it on his layout, it just sat there, making some strange noises that sounded like the speaker crackling. He brought it to me to take a look. I haven’t run O-gauge trains in about 7 years since we moved and my new basement doesn’t have enough open space to run the bug curves I needed, but I still have my DCS system and enough things to test engines.
First I tried to just hook up a length of test track with a Z-1000 setup. When I put power to the rails, nothing happened. If you touch the train to move it the slightest bit manually, it makes crackling noises that sound like they are coming from the speaker. No lights come on at all.
I hooked up the DCS system and got things going with a Z-1000 brick fed through fixed voltage 1 input. Same thing. It cannot add the engine at all either, it never finds it.
I opened it up and found no wires broken inside. I did find that it has likely been opened before. It was missing some screws on the bottom of the chassis holding the shell on, and 2 internal body posts were broken (not a real problem), 1 with a screw in it, and the other stuck to a wire it had been pinched against, probably at the factory. The main proto-sound 3 board has a plastic tray under it, and that was all bent out of shape as if someone had worked on the train before, or it could have been that way from the factory. I double checked all the wire harnesses to make sure they were all fully plugged in.
That's about as far as I can go with it. I'm no electrical engineer. I'm hoping that someone here may have had a similar issue and found the problem. Otherwise, he may end up converting this to a dummy unit.