Model Railroading > Perplexing Running Problem on tow Athearn SW1500's

So I have a number of the SW1500's of the later Athearn runs...one is the PC 9227 in these videos - the other is a CN....these units are hard-wired at the factory from trucks to power board.

I own a number of these and only these two exhibit the problem found in the videos. They will not run continuously - instead powering off and on intermittently. 

The videos show thw problem. I have taken them apart twice and checked the following:

Power continuity through wheels to decoder -ok
Changed decoders - no difference
Wheels - clean
Track - clean
Power continuity through turnouts - no issue (Trackmobiles run through them...) 
Internal wiring connections - all seem to be ok and tight.
All wheels touch rails - confirmed

Only thing I can find is that the "skipping" problem occurs more at higher throttle levels than at lower ones.This suggests that the added torque may be rocking the unit and causing a connection to come loose?

It is not a shorting as it does not trip my DCC breakers or interrupt sound in units in the same power zone (booster). 

.....when they do run short distances they run really smooth.

Anyone have any wizard ideas on what else I should check?

Have not checked the motors themselves....perhaps intermittent brush contact?

Bob





 

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That problem looks to be an intermittent short or loss of contact.  I would dismantle the trucks and look for loose metal parts that might be 'almost' coming in contact with one another.   What you might try is to run the unit holding it in position while observing the lights for flicker, and rocking the engine gently side to side etc, before you investigate the board.  It is clearly vibration /rotation  caused intermittent.  Sometimes a motor can have a bad winding that can produce such a problem; If you have an extra, swap it out and see it there is a change.  When I encounter something like this that is not obvious, I do a thorough tear down and reassemble,  fixing problems and potential one along the way--makes for a better operator anyway.  Another thing to check, is the contacts of between the wires and the board.  On occasion, I have found them to look secure, but actually be defective under the little black plastic caps. Good luck.



Edited 1 time(s). Last edit at 07/24/16 12:16 by g-spotter.

Is the motor armature clean?  Definitely appears to be a short...

sphauler  

         Can you just set them over to a 'dead line' during operation sessions ?     :)

Hi there.

That's bloody annoying. I echo what someone else mentioned above. The headlight flickering when the unit is travelling along to me seems like its a power supply issue. My reason for saying this is that if the power supply was constant and not interupted the light would remain constant, this is not the case as it flickers. Therefore in my mind it has to be a power supply problem. I would remove the body, remove the truck side frames and re-solder the connections between the bogie side frames and the decoder track power wires. As you say, you've tried different decoders, clean wheels and clean track so what else could it be. Having said that check that the current is getting between the axles and the bronze type bushes. I had a Bachmann (yes no jokes please) GS4 steam engine that exhibited a similar problem. I traced the fault to a lack of conductivity between the axles and the rigid frame (too much lube and some grime doesn't make the power flow). Whilst this loco (yours) isn't a Bachmann model, I wonder if thats a contributing factor. Although it would be highly unlikely!

Hope that helps. Keep us posted.

Cheers,

Allister 
New Zealand.

I have a RTR Athearn SW1500 with the same issue. I would say its not a short but a power loss issue due to loose wire or component. I need to open mine up and get it figured out as it is an aggravation.


                                                           Regards, Dave Dane

Could also be a broken wire. One close to a moving part like a fly wheel. Might be rubbing at only higher rpms. Last time i had that happen it was a broken wire at a solder joint. Only two strands actually holding it on the others broke.

I agree that it is not a short...I have monitored the electrical situation on the layout and induced shorts and the effect on the layount is very different. Were it a short, when the loco stopped because of it, the layout would shout down but nothing happens. This is definitely as some of you suggested indicates  a "tear-down and rebuild"  effort is  required. I'll let you know what I find....

Bob

grandeguy Wrote:
-------------------------------------------------------
> I have a RTR Athearn SW1500 with the same issue. I
> would say its not a short but a power loss issue
> due to loose wire or component. I need to open
> mine up and get it figured out as it is an
> aggravation.
>
>
>                          
>                          
>          Regards, Dave Dane

"....these units are hard-wired at the factory from trucks to power board."

Athearn commonly uses the plate at the top of the truck which supports the frame as one of the power feeds. You will find a grommet swedged into the frame or a wire with a screw connection which carries the power from the frame to the mother board. This leaves a sketcky connection between the truck and frame. So while the model is apart for service solder a wire to the truck bearing plate which does not have a wire connection then route that wire from each truck to the mother board replacing the Athearn wire from the frame.

Posted from iPhone

Bob if these have the square bearings that ride in a stamped steel slot check and see if the steel is painted on the slot edge. Years ago Athearn just left the steel unpainted but on the newer units they now paint the steel for better appearance. Sometimes they paint the edges of the slot where the bearing rides and this also is the electrical path from the wheels to the decoder. Pop off the bottom plate pull out the axle wheel assemblies and take a look. ----   Ken 

Odd. I have several of these and none have had this issue.

I just did a Loksound, LED amd keep alive instal in one. Cant beat hardwiring.

Posted from Android

I don't think this issue is limited to just the SW1500 either. I've had the same madding issues with many of their newer two axle trucks including the GP9, MP15 and to a smaller degree the GP38-2. 

Although I've not found a rock solid fix, cleaning the axle/bearing area and adding a drop of conductive oil goes a long way to improving performance. 

I've done the whole "solder everything" trick on several units with no effect. All my units are DCC sound equipped.

I'm convinced the issue is a connectivity issue between the axle and the bearing. Wipers are most likely the cure but I haven't gone there yet.

It will be interesting to see what you find. 

Chris