DD40AX electrical pickup

[cybr]

I just got this locomotive.  But it seems like the electrical pickups at the trucks don't make full contact.  If I push down slightly, it will go, otherwise it will stop and not move.  Any tips on what to do?

[skipgear]

It's probably the contact between the decoder board and the top of the chassis. They contacts are via friction  contacts under two screws and if they are not tight this can happen. If you feel like tinkering, pull the shell off and adjust the contacts and or the board. If not, send it back to Bachmann.

Here is what to expect under the hood...

[cybr]

Thanks, I'll take a peek at it tomorrow.

[cybr]

Took the shell off,  using slight pressure on the PCB it would light up and move.  Let go and it would stop including the lights.  Pulled the PCB off, noticed that the brown wire to the motor was nearly severed, patched it and no difference.

[cybr]

I'm sending it back to Trainworld, and they will be sending a new one.

[cybr]

Got my replacement from Trainworld and it works great.

[mywhitedog]

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.

[mywhitedog]

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.

[mywhitedog]

My DD40AX now has a MRC 1959 sound decoder!

[mywhitedog]

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!

[skipgear]

Did you use two decoders? You can't use BEMF if you have both motors connected to one motor. The BEMF feedback from two motors would confuse the heck out of the decoder. The load of two motors on one decoder is probably what is causing your startup problems also.

As far as mechanical issues, look for binding in the trucks. The new doodlebugs have this issue, the screws holding the side frames together on the trucks are too tight. Backing them off a 1/4 turn makes a night and day difference.

Even the new Bachmann HO version is using two decoders for sound. It is the only way to do it right becuase there are two completely seprate power systems in these things in the real thing. The engines are not connected and do not sync exactly with each other.

[mywhitedog]

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.

[skipgear]

You are still going to have a problem with two motors on one decoder, especially if you are using BEMF. It goes into a long thesis on how BEMF works but put it this way, two motors, spinning out of sync from each other are going to send mixxed signals back to the decoder. BEMF is going to be useless and cause more headache than good. Use one decoder for one motor, the other for the other motor and then play around with the speed tables on the M1 to get it to match the MRC decoder. It will be a little more work but I think the results will be much better.