Which track?  Does the

Which track?  Does the problem happen on regular track or when going through a turnout or a crossing?

If the problem only occurs going through a turnout or crossing, the power pickup from one or more trucks may have an intermittant connection.

Does the problem occur on straight track, a left curve, or a right curve?

If curvature makes a difference you may have power pickup troubles with one or more trucks.

If the problem happens pretty much everywhere  you might try determining if the problem is electrical pickup from the track or in the decoder (or motor).

Take the loco off the track. Disassemble it enough to be able to put clip leads on the track power wires going into the decoder (black and red wires). Turn off the track power. Now connect the clip leads between the decoder (black and red wires - doesn't matter which wire goes to which rail) and a piece of track.

Turn the track power back on and select the loco with a throttle. If it runs smoothly, chances are you have an electrical connection problem between the wheels and the decoder track power inputs. Get out your magnifying glass and check that all the wires are attached where they should be. If this loco has wheel wipers, make sure they are not bent or damaged or inundated with grease or oil.

If the the loco stops and starts as before, you may have a motor problem, something jammed in the gears, or a decoder problem.

If you have another decoder try connecting it up to the motor and see if it works smoothly. If not, you'll need to do some more disassembly.

Remove the motor and make sure that the wheels and gears all rotate smoothly by twisting the drive universal joints with your fingers. If there is a lot of resistance to twisting or if the resistance comes and goes as the wheels rotate there's like to be something out of kilter in gears - probably in the universals or the splined half shafts on the drive shafts leading to the trucks.  SInce the third truck sort of trails behind, it's likely that a problem would be in it's gear set (which would be more easily damaged by rough handling).

If the gears spin nicely, try running the moter while it's disconnected. If it starts/stops you'll need a new motor (unlikely in these days of can motors).

Hope this gives you some ideas...  Good luck!

Charlie

Not sure if its your problem

but the lesson I learned from my first Tsunami install was that the power connections from the truck pickups are best hard-wired, not simply using the pickup strips.  In my case, I could get sound but no motor movement at all, and then nothing, then sound, then nothing.  Since it was my first install, I just assumed I screwed something up and sent it off to Litchfield.  They explained that it was just an issue with unreliable power from the pickup strips and they hard-wired it and its worked like a charm since.

I have the same shay

I was having the same problem after I added the soundtraxx sound decoder and found out that the Bachman and the soundtraxx were switching back and forth from one to the other.

When one was low the other was high and my engine would start and stop on it's own. Since the soundtraxx is both DCC decoder and Sound decoder I pulled the spectrum 8 pin chip and just plugged in the soundtraxx and no longer have any problem..

Dan

Spectrum Shay

Maybe the below link will be some help.

http://www.all-model-railroading.co.uk/forum/showthread.php

Rich

Spectrum Shay

I appreciate all the input.  The problem occurs on straight track, curved doesn't really matter.  I bought the engine without decoder or sound and added the Sound Trax.  I will take it apart and see if the pick-ups are making contact and check for excess oil and grease.  Anything at this point will be worth a try.

+ +

Might I suggest you take each truck apart and clean the brass contacts where they meet the side frame. Over oiling the wheel axle to frame will cause bad pickup.  Then the brass pickup of the truck to the frame pads is another point than can cause issues.  Apart from those the rest is wired and soldered so should not cause issue.  Sometimes forming the brass truck pick up each side of the bolster, as shown in my picture, can help matters. One screw to remove and check the truck contacts.

Did you remove the small capacitors from the Bachmann board when you added the soundtraxx decoder. They are known to cause erratic operation where DCC is involved.  They have capacitors and chokes on the board that are not required in DCC.  You can cut the capcitors and replace the chokes with wire jumpers.

I've got one of mine apart to change all bulbs for leds, add sound and move the TCS decoder into the coal bin. Got my hands on an older Soundtraxx Shay sound only decoder but it was a tight fit for both the TCS and the Soundtraxx in the tendre.