I recently purchased a Proto 2000 E-7 (new old stock) and it runs perfectly in DC mode. I have brought it to my club layout several times and it runs very nicely. Last week I decided to convert it over to DCC. I have several other Proto 2000 E-7’s that I have already installed a DH163 decoder in. It’s really pretty easy, remove body, remove 8 pin dummy plug, install 8 pin wiring harness and decoder, program on programing track and run.
On my first attempt to program it, it would not respond on the programing track so I then went and attempted to program it on the main. As soon as I did this, the decoder fried.
Thinking that maybe I had a bad decoder, I purchased another one (DH163) and tried again. Once again, nothing on the programing track. Went to the main line track to program it and once again, nice smoke show from the decoder.
Again, with the dummy 8 pin plug installed, it works great in DC mode.
Somewhere, somehow, power must be going to the frame or otherwise conducted in a manner that’s disastrous for decoders. I would start by testing the wiring with a multi-meter to see if there’s a path to the frame someplace. I would clip one lead to the frame and touch the other lead to all the wires and/connections checking for continuity. If I get a continuity reading I know that wire or connection is grounding.