# Swapping polarity?



## cape cod Todd (Jan 3, 2008)

I bought a second hand 38 ton shay that has a phoenix sound board in it. The original owner did some custom wiring to put in that system. 

The trouble is the shay runs in the opposite direction as the rest of my engines. The easy fix would be to open the smoke box door and flip the polarity switch back there but that has been disconnected. The on and off switch works the sound system.

How can I get this shay to run in the right direction? Is there wires I can switch on the main board or somewhere else to change the polarity?

Do the pickups at the motor blocks need to be swapped?

Thanks


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## toddalin (Jan 4, 2008)

OK, the engine runs "backwards" from your other engines. But before you can address the fix, you need to determine if it is running forward or backwards with respect to the sound system.

When you start in a forward direction, the engine should sound two toots. It should sound three toots in reverse.

If the train runs forward with two toots, you need to change the polarity from the pickups where they enter the "board" to reverse the direction of "everything."

But if the train runs forward with three toots, you need to change the polarity between the board and the motors.

The sound card may include its own lighting system, and this should restore the proper operation of the green and red lights and/or frward/reverse lights, if so equipped.


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## Treeman (Jan 6, 2008)

The Phoenix program can be changed to take care of the reverse toots. Would require the program interface.


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## Dan Pierce (Jan 2, 2008)

If lights and engine are in the same direction, just track power needs reversing.

There is a wiring diagram on the Bachmann site for the 38 ton 2 truck shay which shows the colors of the various wires.


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## cape cod Todd (Jan 3, 2008)

I tested the sound and sure enough the board was giving 3 toots for forward and 2 for back. I reversed the wires on the board and it fixed that but the loco is still moving in the wrong direction. I traced wires to the main board and swapped them but then the loco didn't move so something was crossed. Swapped it back and it still runs, glad I didn't blow something out. 
The lights work with the proper direction. 
I do have a wiring diagram for the 38 ton shay but upon closer inspection the Bachmann board has been replaced with I don't know what. It is a small board mounted next to the phoenix and there is also a rectangular block about 1/2x 1/2x 3/4 where several wires are attached? I know it could be anything. 
It figures, there is a 50/50 chance that this would be the wrong way. 

I will tinker with this more today. Thanks guys.


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## toddalin (Jan 4, 2008)

cape cod Todd said:


> I tested the sound and sure enough the board was giving 3 toots for forward and 2 for back. I reversed the wires on the board and it fixed that but the loco is still moving in the wrong direction.
> 
> I will tinker with this more today. Thanks guys.


This is what I was saying. What you did was change the _polarity from the main board to the motors_, but you needed to change the _polarity from the pick-ups to the main board_ to reverse everything.


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## cape cod Todd (Jan 3, 2008)

Thanks guys I was able to swap the polarity after carefully tracing the wires. It turned out to be the grey and orange on the mystery board. The trouble is now the head and rear lights are not lighting properly with the chosen direction.? 
I did swap the wires on the sound card so it gives 2 toots for forward and 3 for back. I also got the firebox and ash pan glow working again. The wires had snapped off. 

Another question is what is the mystery board? It is not Bachmann. I don't know how to post photos here but did put it up on largescalecentral site with the same polarity swap question. Here is the link. 
http://www.largescalecentral.com/forums/topic/23404/help-changing-polarity

Thanks again.


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## toddalin (Jan 4, 2008)

cape cod Todd said:


> Thanks guys I was able to swap the polarity after carefully tracing the wires. It turned out to be the grey and orange on the mystery board. The trouble is now the head and rear lights are not lighting properly with the chosen direction.?
> I did swap the wires on the sound card so it gives 2 toots for forward and 3 for back. I also got the firebox and ash pan glow working again. The wires had snapped off.
> 
> Another question is what is the mystery board? It is not Bachmann. I don't know how to post photos here but did put it up on largescalecentral site with the same polarity swap question. Here is the link.
> ...


Are you running the lights from the sound card, or are they taken from the pick-ups?

If from the sound card, they should sync to the toots, so if they don't, perhaps the "headlight" and "tail light" wires are switched on the card and you can easily change their wire's positions.

If they are wired to the truck pick-ups though diodes, you may need to turn the diodes around or put them on the other "leg" to retain their orientation. But, if they are wired to the truck pick-ups, previously they should have been correct for the motors, so when you switched your motor wires to get the train to run the "right way" it sounds like to switched them at the motors and should have switched them at the pick-ups, so that the direction the train travels and lighting still track together, and maybe it is better to put it back to this orientation and switch the motors and lights together by changing the polarity at the pick-ups.

You'll get it.


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## Dan Pierce (Jan 2, 2008)

I hope you did not change the wires in the coal/oil bunker.
The real wiring on the one I worked on was under the firebox.
The large plate on the middle bottom is removable and the board can be extracted and worked on.
There are many wires on one corner for track power.

The small board in the tender of mine was for chuff sensors.


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## MikeMcL (Apr 25, 2013)

Mystery solved. Board is a digitrax decoder. He swapped the orange and grey to change the motor direction, now needs to swap white and yellow for the directional lighting. Or since it is now running on straight DC, the pickup wires to the board (red/black) could be swapped.

Just put this here in case someone stumbles upon this situation. Easiest solution is to take the loco to someone with a DCC programming track to change the CV that controls direction.


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## cape cod Todd (Jan 3, 2008)

Thanks for all the info guys. I just buttoned the shay back up for now and I will have to live with the lights the way they are. I had a second and third look at them and it is tough to tell just what is what plus there are diodes involved. There should only be 1 purple wire but there are 3 in there. Yes it will bug me come this running season but oh well I am happy enough that it can now run in the right direction with my Heisler and Climax.


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## Dan Pierce (Jan 2, 2008)

Just swap the wires going to the lights if you can trace them out.


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## Dick413 (Jan 7, 2008)

Mike that is just what i was going to say put all the wire back to the way it was and just change CV29 to 3


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## Dan Pierce (Jan 2, 2008)

One can not change CV29 if they do not have DCC, that is why I said swap the front and rear light wires.


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