Large Scale Central

Help Changing Polarity

Electronics Power and Sound
#1

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

#2

If it is a Bachmann 2 truck Shay, as manufactured, the polarity is fixed within the trucks.

#3

Maybe polarity is the wrong word but there is a 3 position switch behind the smokebox door of most Spectrum models that turns the loco OFF or sets the direction to NMRA standard or Large Scale. This switch when functioning properly will change the direction of the loco.

The trouble is mine has been disconnected and set to go one way, the wrong way on my RR. It turns out the Bachmann board has been replaced with a mystery board. I will have to take and post a photo of it.

#4

Use a DPDT switch. It’s wired in an X… the leads come in from one side and cross over to the opposite poles on the other side. Motor leads are off the center poles, flip the switch if she’s backwards.

John

#5

There has to be power leads coming from the trucks to the board, the mystery board. You would need to determine what wires are the power pick up wires and reverse them, from both trucks.

#6

It should be easy enough to swap the wires around but so far… I don’t want to blow this thing up so need to proceed carefully.

Here is a photo of the mystery board. Does anyone recognise it? The only markings are on the white part “RS”

There is also the thing at the top of the photo that has wires going to it and I think some have broken off but haven’t affected the loco.

I did swap the wires on the soundboard and now it toots twice for forward and 3 times for backing.

#7

Battery or track power? If battery, simply reverse the leads coming off the battery.

#8

Steve, I believe its track power, and reversing the leads off the battery to a controller board is probably not a great idea. Reversing the leads from the battery power control board to the trucks would be a better option.

Todd sounds like you are making progress, and yes its best to proceed with caution.

#9

Making progress! I found the proper wires to swap after tracing them. It was the orange and grey seen on the mystery board. Success!

I was then able to set the sound board wires so 2 toots forward and 3 back. There is one more problem that needs ot be addressed, now the headlight and rear light are not workign in the right directions.

#10

Todd, it sounds like that locomotive was wired all bass ackward. But once it actually runs properly, you will be happy and proud that you were able to fix it.

#11

David Maynard said:

Todd, it sounds like that locomotive was wired all bass ackward. But once it actually runs properly, you will be happy and proud that you were able to fix it.

So true David. I bought this over the Summer so ti has had track time and it is cool BUT when I put another engine on the same track, I like to run 2-3 at a time on the main it went the wrong way. I have finally gotten around to it now to set it straight. It was probably fine on the prior owners RR but it was oposite to my LGB and other Bachmann engines.

The trouble is the mystery board. I have the wiring diagram from Bachmann for this engine. If I had the diagram for the mystery board it would be easier to trace wires. Electronics are not my strong point.

I got this engine for a good price so some tinkering to get it right is a pain but part of the dynamite deal.

#12

I have the old 2 wire truck diagram.

Only way to reverse this unit is to flip the motors in the motor block, or rewire the motor blocks for 4 wire operation.

Since I was doing a DCC conversion, I added motor wires to both blocks and ran them to my DCC board in the fuel bunker.

Here is the diagram for the old engine with no reversing switch, 2 wire motor block.

http://freightsheds.largescalecentral.com/users/piercedan/WiringDiagram.jpg

#13

I don’t have one of these engines but - -

I have changed direction on a few of my EBAY bargains

by opening the motor block unsoldering the motor leads

and rolling the motor 180 degrees and re-soldering the leads

Maybe one of the guys that have one of these can tell if this can be done on this loco

Bill

#14

The mystery board looks just like a Digitrax DCC decoder. If you remove it, please send it to me, LOL!

Here is a page you can download a diagram, http://www.digitrax.com/products/mobile-decoders/dg583s/

#15

I say mystery solved Mike ! It looks just like that. Would you happen to have the original board for a 38 ton shay? We could swap.

The lights were working properly until I swapped the wires on the DCC board to change the polarity and direction of the shay to match all my other equipment. inside the smoke box door is the switch for the smoke, which has been removed and another for NMRA standard, OFF and large scale.

I don’t remember if the directional head and tail lights worked properly before I swapped the wires on the sound board to get the toots right. I might have to go back and check that.

Instead of rewiring the motor block can’t I just cut then reattach the wires properly that go to the lights? I wouldn’t even mind if both lights were on all the time.

The engine ran fine when I got it, it just ran the wrong way compared to my other engines.

Thanks for all the info.

#16

Todd Haskins said:

I say mystery solved Mike ! It looks just like that. Would you happen to have the original board for a 38 ton shay? We could swap.

The lights were working properly until I swapped the wires on the DCC board to change the polarity and direction of the shay to match all my other equipment. inside the smoke box door is the switch for the smoke, which has been removed and another for NMRA standard, OFF and large scale.

I don’t remember if the directional head and tail lights worked properly before I swapped the wires on the sound board to get the toots right. I might have to go back and check that.

Instead of rewiring the motor block can’t I just cut then reattach the wires properly that go to the lights? I wouldn’t even mind if both lights were on all the time.

The engine ran fine when I got it, it just ran the wrong way compared to my other engines.

Thanks for all the info.

Since you swapped the grey and orange to change the polarity of the motor, the lights would operate in opposite direction of travel. I would also swap the white and yellow wires. White normally would go to the headlight, yellow to the rear lights. The blue wire is common on both.

If you want all lights to stay on regardless of direction, combine the white and yellow wire.

#17

BTW, I could’ve saved you a bunch of rewiring. Just find someone with a DCC programming track to change the CV that controls direction of travel :wink:

#18

Thanks for all the help Mike and the rest. I am going to leave the lights for now. I can’t figure the wiring out, there are 3 purple wires whene there should only be one and extra white wires too. Some of these pigtail into others and there are diodes involved. I’m happy enough for now that the Shay will now run in the same direction as the rest of my locos. Someday I will get the lights setup right but it is good enough for now.

#19

One rule of thumb when you have DCC decoders in a loco, even when operating it from DC.

Get the decoder running correctly under DCC, that will synchronize the lights, sounds and direction of travel. Normally this involves the swapping of the motor leads if the lights are backwards.

Then if it runs backwards on DC, reverse the track pickups.

Then the locomotive will run correctly in all modes.

You can download the Digitrax manual which will show the connections to the decoder board.

Greg

#20

Todd, you can swap the light wires on the decoder as the decoder has a F front and R rear output, just swap these 2 wires.

Download the Digitrax manual from their site.