I added a TCS M1 decoder for movement and lights, the MRC 1959 is now sound only, also removing the Bachmann board, all I lost was the flashing light on top, but I didn't care for it anyway. The loco runs smooth now and at low speeds, I guess the MRC decoder just couldn't handle both motors. Had to go to a smaller speaker, it went where the capacitor sat on the old board, the sound decoder is in the tank on the bottom. Now to find something to go in that hole where the flashing light was.

The loco is still running and sounding great, the only downside to this loco from the beginning no matter what decoder I put in it, it will not run at a crawl, and the BEMF is not useable the loco becomes jerky. I have a feeling it's the dual can motors. I have cut the start voltage to 0 and top voltage to 10 this has helped, just doesn't have a very good low end speed. I still have the original PC board just the decoder has changed, due to that flashing light on top, which really looks way out of scale. I may just pull the PC board and place a dummy light in the place of the flashing one. My Bachmann GP-7 with TCS CN-GP decoder runs better than this monster!

I've stopped using Digitrax decoders, moved to TCS decoders, the M1 is smaller than the Digitrax DZ123 or DZ125, and with auto BEMF, the cost is a bit more a few bucks, but well worth the money.

My DD40AX now has a MRC 1959 sound decoder!

Update the wheel assembly can be popped off and the pickups lightly bent for better contact, also pulled the Digitrax decoder and replaced with a TCS M1 with auto BEMF. Made a big difference.

I had pulled the Digitrax decoder out of the GP40 and put it in another loco, and have since replaced it with a TCS M1 decoder, its a tiny decoder and fits nicely under the area where the headlight goes. I am also using the Digitrax PR3 and computer to program the decoders, I have it tweaked just right, the BEMF works great. The TCS decoder is so much easier to set up than the Digitrax decoder, also pulled the Digitrax decoder out of the GP7 and replaced with the M1. Being a gluten for punishment, I put a MRC 1959 sound decoder in my DD40AX, minor milling, and weight replacement in the tank where the speaker goes.

The shell removal is a pain, same with the DD40AX.

One point to make here, is that not all DC loco's are good candidates for conversion. If the DC loco runs real good at low throttle positions then do it, if not, don't waste the time, money and milling effort. You will not be happy with the results.

I tried all the contact tweaking, just would not run smooth, I already had the Digitrax decoder so in it went, made a huge difference, the GP7 decoder went into a GP40 loco I had.

I pulled the decoder out of my GP7, and replaced it with a Digitrax DZ125 with BEMF. WOW what a difference!! It's the smoothest running Bachmann loco I have now, I am now considering pulling the decoder out of the DD40AX and replacing it with a Digitrax decoder. For the lights I used a light board removed from a Kato loco, cut the traces and replaced the LED's and added the resistors. No cutting or milling required. It's quiet and smooth running in both directions, before it was jerky and reverse was poor. I tried everything listed here and nothing made it run right. Once it stopped running I pulled the board tested the motor with a DC power pack, it ran smooth, so I ditched the decoder and installed the DZ125.

I have an older GP40 about 5 years old, it runs ok... ran ok on DC so the same on both... It was an el cheapo loco, looks to big compared to the GP7, so I gave it a dirty weathered look.. it looks like it should be retired. Since my main line will be Union Pacific, and it's a Sante Fe loco, it will not be used much, probably sit off the turn table in the yard. I also have a 1970's 4-8-4 that will be used as a museum piece in a park, it's one of the worst 4-8-4's made so I have found via the internet. And I learned a lesson with EZtrack, do not glue it down! I am nailing it through the foam board, too many frog failures. I'm still trying to figure out the BEMF.. will let you know when I do.

Quote from: mywhitedog on March 09, 2013, 11:53:30 PM
Mine did a total melt down, stepped away for a second, it jumped a switch and melted the trucks, the decoder board is ok, just ordered new trucks.

Got the replacement trucks, so the loco is running again.

I installed a Digitrax DZ123 in a GP40, minor milling to isolate the motor, I did not use LED's I used the stock bulbs, soldered some of the xtra wire from the decoder, and slid the bulbs back into there places. The first one I did, I milled out probably like you did, motor area and a spot for the decoder, made the light area bigger....etc, did not work out so well, I ended up replacing the chassis and starting over. The first decoder was a DZ125, the DZ123 is smaller and a better fit, no need to mill out for the decoder, just isolate the motor. You would need a resistor for each LED, the instructions for the decoder should say so. The decoder fits nicely under the headlight area, I used a small piece of electrical tape to hold the decoder up off the gears below. I may have the decoders switched around, both are small, but one is smaller.

I have been working with the switches and all have the same problem, over time the frog power routing will fail, the problem is the tiny contact that slides from one side to the other across a piece of PC board. I have made replacements on 2 switches so far, but may go to an external type connection. Since I am not using the control boxes that came with the switches, I may use a toggle switch or relay in the future, still working out the details. I am already using toggles, push buttons and relays on the control board for train routing and LED's for direction lighting.

Mine did a total melt down, stepped away for a second, it jumped a switch and melted the trucks, the decoder board is ok, just ordered new trucks.