Polarity Switch

[unk]

We run a 4-6-0 Annie and during operating we have experianced reverse polarity that causes problems wth our power source ( Bridgewerks 220RM).

We notice that while operating the back up light on the tender has a very quick bright flash of light ( last only a split second in time). This happens while the locomotive is running forward and the same thing happens with the front headlight when operatin in reverse.

It appears that somehow there is current being feed to the lights when they should be cutoff from any voltage.

If the locomotive is allowed to continue to operate eventualy it will come to a sudden stop goes immediately into
reverse then to forward and stops because it knocks out the transistor board in the power source. This power source is high amp and very suscepable to even a small amount of reverse polarity.

Note: Operate several Bachmann and other loco's and only experience the problem when using the Annie.

Could this be a polarity switch problem? Any ideas would help.

Regards, Monte Pence
mpence1@hotmail. com

[Joe Satnik]

Dear Monte,

Sounds like inductive kickback, where there is a sudden break in the connection between the loco and the power source. 

The opposite direction LED should flash briefly as the motor inductance tries to keep the current going that it suddenly lost. 

The LEDs actually help take care of (sink) that energy.  I'm sure incandescents do the same, except they're not directional like an LED.

(Correction, you could make an incandescent directional by connecting a diode in series with it...)

I wouldn't want to lose the connection between the motor and the rear LED, as that is it's forward direction kickback sink. 

To guard against that loss, I would put a 28 Volt or so bi-directional TVS (transient voltage suppressor) across the motor leads. 

Back to back Zener diodes 28 volts or so would work in place of a TVS.   motor(+)-----Z<----->Z------motor(-)     

There's a possibility you have bad pickups or wiring problems inside your loco, such as a loose wire, or a loose wire shorting where it shouldn't.

Dirty track and wheels can also cause interruptions in motor current.  How clean are they?

Hope this helps.

Sincerely,

Joe Satnik

[NarrowMinded]

I would check the switch for sure, to me it sound like you have a short some where,
Joe may be right, but I would remove a wire from one side of the switch tape it and run the locomotive to see if the symptoms change. if it runs fine then your switch would likely be the problem. I have had switches break inside before and cause similar issues with other types of devices. the wires from the switch could allso be shorting else where.

NM

[Joe Satnik]

Dear Monte and All,

An incandescent cab light that works in both directions could take the place of a TVS or back to back zener diodes for a motor current sink.

A motor getting its power cut off naturally sends a reverse voltage spike on the motor wiring.

When the wheels make contact again, I suppose the reverse voltage could be strong enough to confuse the power supply.

Dirty track and wheels interrupt power to the motor. 

Again, clean your track and wheels, and check for bad/loose wiring and bad loco wheel electrical pickups.   

Put a very thin coat of Wahl clipper oil on the rail heads and loco wheels, and some concuctive lube on the electrical pickups.

Hope this helps. 

Sincerely,

Joe Satnik     

[unk]

Joe - Will follow-up per your suggestions. The first time we had this problem with the Annie it had very little run time and was on clean track (indor layout). Second and third time on out door elevated track that was resonably clean. I have been able to run the loco by using a Tech II power supply. With the Tech II we periodically get the, jerky/jerky, stop,reverse and forward motion but it has not knocked out the Tech II (less amps?).

NM- Will check for loose wires and check the polarity switch.

Thank you both for taking time to help.

Monte

[Joe Satnik]

Monte,

It just hit me...

Is your front truck turned around the wrong direction?  There should be an arrow pointed forward on the truck. 

Are your main driver electrical pickups plugged in correctly? (Remove loco bottom cover.)

Another way to check would be with an ohm-meter on the lowest setting. 

On the bench, off any track, tender disconnected, check to see that all 5 left loco wheels are connected to each other,

and that all 5 right loco wheels are connected to one another.  You should get very near zero ohms. 

If you see motor resistance (between 2 and 10 ohms?) between the same side front and rear wheels,

that is confirmation that your front truck is turned around.

If all your wheels check out, you should be able to see the resistance of the motor from any right wheel to any left wheel. 

Hope this helps.

Sincerely,

Joe Satnik

[unk]

Joe-

We did make sure the front truck was in the proper position. Will get her on the bench do the inspection and ohm test.
Will be a couple of days and will advise the results.
thanks again.
Regards,
Monte

[Joe Satnik]

Dear Monte,

It's possible that the middle (blind, or flangeless) driver wheels may not have electrical pickups on them.

Hope this helps.

Sincerely,

Joe Satnik 

[Joe Satnik]

Dear Monte,

Here are the Annie wiring diagrams:

http://www.bachmanntrains.com/home-usa/dwg/dwgs/81099.pdf

Scroll down to page 5 of 6. 

Hope this helps.

Sincerely,

Joe Satnik

[unk]

Joe-

The wiring schematic - a big help.
I don't have anything to report at this time due to other commitments that are causing delays to railroad engine repairs.
Will follow with test results.

Thanks to all for your help.
Monte