4850TM Trackmobile

@DougH posted:

I recently purchased a Lionel 4850TM Trackmobile and once I successfully programmed it, I discovered an issue with it. The couplers spontaneously open whenever is on the FasTrack Operating track (#6-12054). This may happen any place on that section and not just over the center magnetic. It happens about 90% of the time. I have about 10 of these Operating Track sections and it occurs on all of them.

The Operating Tracks use a separate power source so I have even tried disconnecting their power and the issue still occurs.

1) Are your two power sources phased?

2) If two different transformers are out of phase, but there is another electrical path that completes an unanticipated circuit between them, voltage could still be present at the Operating Track with one of the leads connected.  When you disconnected the separate power source to the Operating tracks did you disconnect both leads or just one?

@DougH posted:

I’m using FasTrack with a Legacy controller. None of my other Lionel engines have this problem.

3) Are you referring to other locomotives with electro-couplers?

@DougH posted:

... when the sliding contact shoe goes over the control rail.

If your Trackmobile looks like this one underneath, there don't appear to be any sliding contact shoes to make contact with the Operating Track's Auxiliary Control Rails.

4) Are you instead referring to the center rail Pick-up rollers making inadvertent contact with the Control rails?  You may want to check to make sure the pick-up rollers are not bent to either side (angled off the front to back center-line axis).

5) If your Trackmobile looks different underneath, a picture may help with the diagnosis.

6) What transformers are you using to power the Trains on the track and the Aux Power In on the Operating Track.

7) A diagram detailing the connections between the transformers, Track and Operating Track would also be helpful.

1. I’m using the Lionel transformer ZW250W, where the track uses connection ’A’ and the auxiliaries, Operating Track and switches, using ‘B’ with a common ground.

2. I disconnected the ‘B’ connection.

3. Yes, all the other locomotives have electro-couplers and the work fine.

4. Yes, I’m referring to the center rail pickup and the pickup rollers do not appear to be bent

5. The picture is the same as my Trackmobile.

6. and 7. See #1.

I have noticed play in the trucks that may allow the wheels to touch the control rail.

I suspect that the when Trackmobile shorts, it causes the uProcesser to reset which causes the couplers to open.

According to the Trackmobile manual pg. 9: “Your vehicle’s ElectroCoupler will NOT open manually or by using a Remote-Control Track section.”

Thanks,

Well, I can say it's not a universal issue, and I can't imagine what is going on with yours.  Here's a trackmobile rolling over a Fastrack Operating track several times without any couplers opening.  At the end, I commanded the couplers to open to illustrate they are actually working.  I ran it back and forth at least ten times after the video, never had the issue.

@DougH posted:

I have noticed play in the trucks that may allow the wheels to touch the control rail.

I suspect that the when Trackmobile shorts, it causes the uProcesser to reset which causes the couplers to open.

Doug, Thank you for the additional information. If you suspect the Trackmobile may be shorting on the control rail, checking /correcting the wheel gauge (if necessary) may be a good next step.  If the wheels are shorting to a grounded control rail, that would cause Transient Voltage Spikes to occur.  Under low lighting conditions, you should be able to see sparks when this happens.  The circuit breaker in the ZW is not fast enough to trip if this shorting only happens briefly.  As you may know these spikes can damage the electronics in the Trackmobile and other similarly equipped modern locomotives.