I found out what was wrong and corrected it. I must have gotten a Friday locomotive. The pickups in the trucks were so badly placed that they were making intermittent contact and in some cases were shorting out. I fixed that problem in about 30 minutes. The soldering was very badly done. The wires on the trucks were so poorly soldered that they would come loose with just a gentle tug. 5 minutes of soldering fixed that. Here's the biggie. The motor is faulty. I'm not sure what's wrong with it, but it won't hold a steady RPM. I changed it out with the motor from a John Deere BB F7. The locomotive runs fine now on DC and DCC, no humming, no growling (except a little from the BB motor). The growl sounds quite a bit like a diesel engine. These are problems I would expect to find in a BB locomotive, not a $110 RTR that's supposed to represent quality. If this had been a Proto 2000, Walther's would have gotten it back with a strong letter of complaint. With all this repair work, it has earned itself the title of 'Honorary Tyco Locomotive'.