I have several MTH Proto-2 engines that have never been out of the box. Today, I removed an AC6000 Diesel (20-2265-1) and put it on a test track without DCS and fired it up. Seemed okay at first, but the sound was a bit loud and the smoke unit was on. So I removed it from the track and turned the sound down and turned off smoke. Put her back on and there was no sound. So I tried direction control and nothing. So, I then placed the loco on a DCS loop on my layout, discovered it, started it up, sounded okay, and the loco moved forward on command. Then, the z-4000 transformer's "red light" came on, I smelled fried electronics, then nothing.
Is there a process one should go through when operating early P2 engines, perhaps changing the battery? I wanted to give this to a friend for his grand kid. I have other engines, but don't want to fry them as well because of my mistake.