Hey guys I got this P2K GP9 Phase 1, I am trying to install a decoder but if Plug the decoder in it just shorts and clicks... I checked the motor its fine its insulated, if I cross the pickup power to the motor brushes it runs. Any ideas? Thanks Mike
It's hard to tell from your photos exactly how you have wired the decoder, but it appears that you're only picking up power from one rail through the trucks. The frame acts as the pickup for the other rail.
The decoder's red wire should be connected to the two wires coming up from the trucks. The black wire should connect to the frame. The orange wire connects to the top brush of the motor, and the gray wire to the bottom brush of the motor.
Have you checked the motor brushes to see if they are isolated from the frame? In many locos of this type the motor must be removed to insulate the bottom pickup from the frame. You need a VOM (Volt-Ohm Milliameter to check this. That metal screw in your bottom photo is probably holding the motor in place and could be shorting it out.
Other way around actually. The wires from the trucks are the black wires for the decoder. Right behind the bulge of metal that holds the front light, there should be a screw into the frame which connects to the red wire. The top motor brush is the grey, the lower brush orange. It's the same mechanism and chassis at my GP-7 except for the -7 they color coded all the wires.
The metal screws (there should be two) hold the frame casting/weight to the chassis. The four black spots in the other 4 hols are the plastic motor mounts.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
First, the wires were coded but I actually like to upgrade all the wires if I can't find a short because it rules out all problems in wires. Second, the ground screw is there. But if you said the motor clip do you mean the brass piece that retains the brush springs?. I would really apperciate it if someoe could give me some clear close up photos on how they wired a simular wire. Thanks, Mike
PS: I have both brass screws to hold weight to the frame I only put one in to save time, I actually run a business repairing models but I mean I am very knowledgable in the field and I have the proper tools to find and repair the problem. But I am just puzzled I have checked and rechecked, but I just can't figure it out, no shame in asking and finding out, that's how you learn right?
I think somewhere on my web site I have linked photos of similar P2K locos, the problem is every one of them will have color coded wires as I don;t replace the stock wires. All I've ever done with any of them is connect the like colored wires to the decoder and they've always just worked. I do swap out the lights for LEDs with 1K resistors, but the rest of the stock wiring stays in place. The one that was a ahrd wire was the SD7. My previous GP7's I just used Digitrax SH163L0 decoders which drop in place. The most recent one I have I hard-wired a TCS T-1 decoder but I haven't taken any pictures of it yet. But like I mentioned, it's just a decoder with a wire harness with the black decoder wire connected to the black loco wire, the red decoder wire attached to the red loco wire, etc, and the joints covered in shrink wrap.
That is what I mean by the motor clip. The original wire on top attached to the motor under the plastic cover that retained the front light. Since you repalced the wire, did you leave a loose strand, or too large a blob of solder so it is touching the weight? Or the same for the bottom motor wire.
[edit] I also see your replacement bottom motor wire comes up at the front of the motor instead of the back where the stock one did - I'll bet the place you soldered it on is making contact with the chassis down there.
I will look thanks for your help. Mike
I had a similar problem with my p2k 1st generation GPs. You have to really check all the places that can short. The short checks will need to be preformed with a Ohm meter. I found the trucks can touch the frame or the weight in many places. Check the wheels to the frame in any kind of turn. Also with the 1st generation, the clicking could be the split gear disease that can develop on the wheel set gears. This is easly repaired with a set of athearn replacement gears.
Barry S.
CCMRC