Change polarity on Bachmann F7

[IndyRRman]

I have an old Bachmann F7 (DC) on a DCC layout.  It runs the opposite direction than my DCC engines.  How difficult is it to rewire the diesel so that forward on the throttle is the same direction as the DCC locos & what wires need to be changed?  Thanks.

[KiwiSteam]

Hello there, Swapping the wires over on the motor brushes should do the trick.Unless it's a split chassis type frame. I have just modified a SD40 ready to fit a dcc chip,That was fun! Cheers KS.

[jward]

you can rewire a dcc locomotive, but why would you want to. if the normal direction of travel is different from what you want, simply change cv 29. if the value of cv29 is even, add 1, if it's odd subtract 1. it's just that simple.

[jbrock27]

I think Indy is trying to rewire his DC loco to match the direction his DCC locos run in.  Is that correct Indy?
Is is possible for you to post a picture of the F7 with the shell off?  That should help you a lot with hopefully getting an answer.

[richg]

I have an old Bachmann F7 (DC) on a DCC layout.  It runs the opposite direction than my DCC engines.  How difficult is it to rewire the diesel so that forward on the throttle is the same direction as the DCC locos & what wires need to be changed?  Thanks.

What DCC system are you using to run the DC loco?

Did the loco run in the normal direction when you used DC?

Rich

[jward]

I think Indy is trying to rewire his DC loco to match the direction his DCC locos run in.  Is that correct Indy?
Is is possible for you to post a picture of the F7 with the shell off?  That should help you a lot with hopefully getting an answer.

in that case it would be easier to change the cv29 on his existing dcc fleet than to rewire the dc locomotive. reprogramming can be accomplished without having to take anything apart.

[richg]

I think Indy is trying to rewire his DC loco to match the direction his DCC locos run in.  Is that correct Indy?
Is is possible for you to post a picture of the F7 with the shell off?  That should help you a lot with hopefully getting an answer.

in that case it would be easier to change the cv29 on his existing dcc fleet than to rewire the dc locomotive. reprogramming can be accomplished without having to take anything apart.

I am assuming he is using the zero bit option for the DC loco. The controller is sending a positive zero bit and the loco is running in reverse. If I see this correctly, reverse the two wires form the DCC controller to the track. The DCC locos will not be affected.

In the below link, you can see the zero bit polarity.

http://members.shaw.ca/sask.rail/dcc/DCC-waveforms/DCC_waveforms.html

If you were to attach a DC voltmeter to the rails, you will see a positive or negative DC voltage if the zero bit option is being used. Not being used, no DC voltage, only AC voltage on the rails. I had an old MRC2000 with the zero bit option some years ago and I saw this.

Rich

[IndyRRman]

Appreciate all the quick responses.  However, I really wasn't thinking when I posed this question.
Reversing the pos & neg connections to the track got it to work... as long as all the trains are going that one direction.  A DCC loco knows the difference between forward & reverse, but a DC loco doesn't.  It only knows which direction the current is sending it.  So for a (DC) train going the opposite way, forward on the track will be reverse on the throttle. 

[richg]

Appreciate all the quick responses.  However, I really wasn't thinking when I posed this question.
Reversing the pos & neg connections to the track got it to work... as long as all the trains are going that one direction.  A DCC loco knows the difference between forward & reverse, but a DC loco doesn't.  It only knows which direction the current is sending it.  So for a (DC) train going the opposite way, forward on the track will be reverse on the throttle. 

Good old Obvious Man told me the same. lol
Glad to hear.

Rich

[jbrock27]

Glad to hear that Indy.
I did not know that about DCC.  Now I know and have learned something

[richg]

That link I posted was from a former member here, Jim Banner.
I suggest you save each page as a HTML in your PC. The site might go away in the future and you will have all the page in your PC. Just go onto the File Manager where you stored the HTML file and double click the file. The page will open up in your PC. I have done that with many personal sites that eventually disappeared.
Some of the links have already disappeared.

You can also store this thread in Favorites.

Rich

[KiwiSteam]

I was thinking that you were aligning an additional DC loco to you DCC system, I have done the track polarity change myself.    I have a DCC  loco that is cab forward on dcc but reverse on DC. and it is staying that way,On our exhibition layout,I set it up with another loco,each with 3 or 4 passenger cars.,at a station ,back to back on the same line and set them going,the system is DC and they can pass on a loop.First one back has to go onto a 2nd platform, or it's a Head-on,!All good stuff. KS.

[jbrock27]

Thanks, but no thanks RichG.  I don't run DCC at the moment and don't have any immediate plans to, so I don't have use for the info. 

Is Jim Banner really no longer a member here??

[richg]

Thanks, but no thanks RichG.  I don't run DCC at the moment and don't have any immediate plans to, so I don't have use for the info. 

Is Jim Banner really no longer a member here??

Much of the info I have saved is for the model railroad community, not for me. I try to look beyond my needs since there is a huge model railroad community.

Rich

[jbrock27]

That's really nice of you Rich.