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Discussion Starter · #1 ·
Hi Folks,

I was Hard Wiring up a Athearn SD9 last night with a Bachmann Decoder. I checked the loco before hand and it ran fine on DC. I am using a Hornby Select contoller.

I then isolated the usual suspects and test ran using just the Decoder and all worked fine.

As I am just completing a MIR Irish rail 071 class I needed to add the Head lights using LED's and Resistors in the normal Fashion.

Back onto the test track and all was well for a minute or two then....

The Motor just started to continously run on it own with no control at all. Tried to Re program the Decoder and the motor jerks to suggest it was reading the new address instruction but still it started to roll away. I unsoldered the lights and replaced the engine onto the track and again the same thing happend. I also changed to another Bachmann Decoder and the same thing happened.

Has anyone had anything similiar happen or can suggest what is going wrong here. It is not my 1st dcc installation and its the 1st time something like this has happeneed.!!

thanks

George.
 

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Sounds as though there is a short from one rail to a motor terminal, such that a rectified current is permanently available to the motor. First step is to get an ohmmeter on the chassis, and check if there is contact between either of the pickups with either of the motor terminals.
 

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Sounds like one of the many compatiblity problems the Hornby Select is reported to have with non-Hornby decoders.
 

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Discussion Starter · #4 ·
Thanks Guys,

FYI I have had no issues with the select a run Digitrax and Bachmann decoders for both N gauge and oo with no problems at all. Yep it's basic but does me for the time being.

Also had no issues with the West country sound decoder from Howes!! Great product BTW!!

I did not get time last night to check for shorts as it was gone midnight by when I discovered the proble but will look at the most likley part where there is a short which under the motor where the pick up is against the chassis, I used masking tape maybe not the best insulator?

I will let you know how I get one.

Cheers

George
 

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QUOTE (Georgeconna @ 9 Sep 2008, 21:30) <{POST_SNAPBACK}>Thanks Guys,

FYI I have had no issues with the select a run Digitrax and Bachmann decoders for both N gauge and oo with no problems at all. Yep it's basic but does me for the time being.

Also had no issues with the West country sound decoder from Howes!! Great product BTW!!

I did not get time last night to check for shorts as it was gone midnight by when I discovered the proble but will look at the most likley part where there is a short which under the motor where the pick up is against the chassis, I used masking tape maybe not the best insulator?

I will let you know how I get one.

Cheers

George

***George, it may well be that bottom motor clip, as its usually pressed very hard on the lower chassis to ensure good contact.

Ideally you should grind away some of the chassis metal, then pant a coat of epoxy onto it and let dry for 24 hours to ensure no accidental touches.

if you do not want to gring the chassis, use a thin layer of plasticard not bit of tape - the tape is not hard enough to prevent penetration - if you use tape, it may last a short while but will certainly soften in time and cause a short again'

Richard
 

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QUOTE (philg @ 9 Sep 2008, 22:26) <{POST_SNAPBACK}>Are the capacitors still in situ?? If so get rid of them.....ducking for cover...
Phil :)

***No need to duck, its usually a good question and a valid one - but Athaern never has any in the first place!

Richard
 

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Discussion Starter · #8 ·
Thanks Guys.

No Cap's in this loco, The athearn set up is very simple. The wife loves the TV interferance
!!!!!

I'll replace the tape with Thin card as I have that, Hopefully it should do the trick...

I update you tomorrow when I trail it tonigh all going will with the kids who both have colds.....

cheers

George.
 

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Plasticard 5 thou works well to isolate the motor especially in N gauge where space is limited to say the least at times, i linede the chassis at one end where the motor touches the chassis and it solved any shorting problems.

It was applied with a small amount of superglue and then cut /filed to conform to the inside curve where the motor sits in the chassis

The constant running happened to me as well check where the decoder is sitting where it may have rubbed against the chassis as a nick in the wire can cause a short it had on mine and after advice here checked and found the spot where it had rubbed in the wire, happily it didnt blow the decoder and all is well now with it.
 

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Hi from Cornwall UK. I have had "runaways" by using Bachmann function 3 decoders on the new Hornby DMU motor bogie. You can programme the number in OK, put the model on the track, turn the controller on and it will run fine until you go to stop it. It will either run on, OR stop and then start to move a little at a time even without the controller off !!!! I cured it by fitting a Hornby 4 function decoder and it works fine. I did not have a Bachmann 4 function decoder, so can not say if it works OK with one of those or not. Hope this is of some help. Brian

QUOTE (Georgeconna @ 9 Sep 2008, 08:57) <{POST_SNAPBACK}>Hi Folks,

I was Hard Wiring up a Athearn SD9 last night with a Bachmann Decoder. I checked the loco before hand and it ran fine on DC. I am using a Hornby Select contoller.

I then isolated the usual suspects and test ran using just the Decoder and all worked fine.

As I am just completing a MIR Irish rail 071 class I needed to add the Head lights using LED's and Resistors in the normal Fashion.

Back onto the test track and all was well for a minute or two then....

The Motor just started to continously run on it own with no control at all. Tried to Re program the Decoder and the motor jerks to suggest it was reading the new address instruction but still it started to roll away. I unsoldered the lights and replaced the engine onto the track and again the same thing happend. I also changed to another Bachmann Decoder and the same thing happened.

Has anyone had anything similiar happen or can suggest what is going wrong here. It is not my 1st dcc installation and its the 1st time something like this has happeneed.!!

thanks

George.
 

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Discussion Starter · #11 ·
Hi Guys,

Pleased to say I took a second look at installation and I had two problems.

I took out the motor and connected the power to the bogie picks out which still was connected to the decoder and it worked perfectly. This pointed to the motor isolation being the cause.

I replaced the Masking tape with thicker insulation tape, Swapped around the brass contact strips as the lower one had 2 prongs sticking out that could cut through the tape when the motor was push back into its support holes.

Second problem was with the chassis pick up, this was not great and power coming trhough was intermittent, The contact was beefed up with a bit of solder.

Put everything back together and placed onto the prgramming track and it worked!!!

I then Re-soldered the lights on to the decoder wires and put them back into place and again tested them and they worked fine.

Thanks for the help on this one chaps it was appreciated. It was handy not to spend anothor evening mucking about and wondering if it was the decoder or not and hence a lot of wasted time.

all the best

George.
 

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Great news George,

Glad you got it sorted and settled
 
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