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Testing new decoder via direct connect to programming track

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PED
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Testing new decoder via direct connect to programming track
Posted by PED on Saturday, June 02, 2018 1:49 PM

Had a problem with new Digitrax decoder in an Atlas loco. Just finished setting up identical loco/decoder combo with no problems but this time it would not program. Thinking I may have a connection problem with the loco, I pulled the decoder and hooked it directly to programming track with small aligator clips on short leads to see if the decoder would respond this way. The decoder lights  were blinking as I tried to program it but still no luck. Appears the new decoder is bad.

Is there any reason why my test approach of hooking decoder directly to programming track should not give me a good test of the decoder?

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

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Posted by gregc on Saturday, June 02, 2018 1:57 PM

i'm not  familiar with Digitrax, but the programming sequence for NCE involves reading information from the decoder by sensing an increase in current when the decoder applies a voltage to the motor.

maybe you can find a spare motor that you can connect to the decoder while programing it. 

greg - Philadelphia & Reading / Reading

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Posted by richg1998 on Saturday, June 02, 2018 2:36 PM

Put a 100 ohm, 1/2 watt resistor across the orange and grey motor leads. A motor load is required. I found that solution some years ago on the Internet.

I have done that before.

Explained in the below link. Scroll down a ways.

http://mrdccu.com/curriculum/soundtraxx/tsunami.html

Rich

N

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Posted by MisterBeasley on Saturday, June 02, 2018 5:39 PM

richg1998
Put a 100 ohm, 1/2 watt resistor across the orange and grey motor leads. A motor load is required. I found that solution some years ago on the Internet.

I agree, but I'd suggest an even lower resistance, more like 80 ohms.

It takes an iron man to play with a toy iron horse. 

PED
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Posted by PED on Saturday, June 02, 2018 7:31 PM

My Digitrax decoder is a drop in - no wires involved. Was not thinking that a motor load might be required but will figure something out to add the motor load to the test.

That requirement may be part of the problem trying to program it in the loco. I am not a fan of how Atlas connects the motor leads to the decoder. Just two brass strips that lightly touch the decoder. An opportunity for poor contact. Will try again with decoder in loco and make sure the motor leads have good contact with the decoder.

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

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Posted by tstage on Saturday, June 02, 2018 8:06 PM

Paul,

Are you able to solder the wires onto the motor tabs of the decoder?  An electrically much better connection than anything press fit...

Tom

http://www.newyorkcentralmodeling.com

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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Posted by Old Fat Robert on Saturday, June 02, 2018 10:35 PM

Paul, I agree with Tom on soldering the wires even for testing decoders. I use the NCE "starter" system for my programming and I have several times soldered the the orange and grey wire to the motor and then used clips from the rails to the red and black wires. Nothing else needed, works like a charm, no resistors required.

Old Fat Robert

PED
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Posted by PED on Saturday, June 02, 2018 11:34 PM

I had to solder the motor tabs in a different Atlas loco because I broke  off one of the tabs so I know what you are suggesting. However, before I solder, I will probably just put everything together electrically via wires and clips to check it out. If all works OK, I can solder for final install.

I forgot to note that loco ran fine as DC so I know that the problem is somewhere in the connections.

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

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Posted by rrinker on Sunday, June 03, 2018 12:01 AM

 One problem with a lot of N scale locos is that the factory board is thicker than the decoder, so the factoory DC board makes nice tight coontact just by pinching it all together, but the decoder being thinner fails to make secure contact. If kapton tape is called for to keep the motor tabs from touching the chassis where they fold over the board, make sure that yoou have done this, a short there will fry the decoder. One thing people do is add small blobs of solder to the pads to the friction fit becomes tighter, you can still easily remove the decoder.

                                      --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

PED
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Posted by PED on Sunday, June 03, 2018 7:56 AM

Randy...I have had the "thin board" issue on other locos and have used various tricks to deal with it. However, that is not an issue with this particular loco.

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

PED
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Posted by PED on Monday, June 04, 2018 12:51 PM

Found the problem. Decoder was OK. 

A common feature of N scale Atlas locos is that the motor tabs make contact with the stock light bar as well as a replacement drop in decoder vis small copper tabs that make contact via the springness of the tab. If that tab does not make solid contact, the decoder cannot pass current to the motor. I have had this problem with several of my Atlas locos as I add decoders. That was the case on this problem....poor contact between the decoder and the motor. Once fixed, I was able to program the decoder and all was well.

I don't know about other brand decoders but the Digitrax decoder for Atlas locos have small slots in them that you are supposed to run the motor tabs thru to improve the electrical  contact. I got lazy and had been ignoring this arrangement and just relied with the motor tabs rubbing against the contact point on the decoder board. This matches the factory arrangement with the light board. However, I have found that this only works in some cases. I have found that the only reliable way to make good motor tab contact with Digitrax decoders is to make sure the motor tabs go through the small slot in the decoder contact pad. A bit of a pain but that is the best approach.

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

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Posted by KeithKD on Thursday, June 07, 2018 1:47 AM

Interesting, I am going through this exact thing right now. Converting most everything I have to DCC and am using TCS decoders. All my Kato Locos run just fine with the new decoders. For some reason I am not able to get the Atlas ones to run. I have a home built DCC++ basestation and am using JMRI to program and run my locos. All my Atlas locos will not run even after programming. It shows that everything took correctly with no issues. Ive noticed, as stated above this post someone mentioned that the decoders are a little thinner than the factory boards and I was not getting a good contact on the aft side of the board. Fixed that with a little bit of rolled up kapton to put slight pressure against the board contact on the frame. But still not able to run. Ive looked at those two clips you mentioned and had my suspicions about the contact of them. Your suggestion of routing those clips through the slits in the board will be my next step to try and resolve this issue I have. Thanks.... Keith.

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Posted by KeithKD on Thursday, June 07, 2018 5:25 AM

Interesting, I am going through this exact thing right now. Converting most everything I have to DCC and am using TCS decoders. All my Kato Locos run just fine with the new decoders. For some reason I am not able to get the Atlas ones to run. I have a home built DCC++ basestation and am using JMRI to program and run my locos. All my Atlas locos will not run even after programming. It shows that everything took correctly with no issues. Ive noticed, as stated above this post someone mentioned that the decoders are a little thinner than the factory boards and I was not getting a good contact on the aft side of the board. Fixed that with a little bit of rolled up kapton to put slight pressure against the board contact on the frame. But still not able to run. Ive looked at those two clips you mentioned and had my suspicions about the contact of them. Your suggestion of routing those clips through the slits in the board will be my next step to try and resolve this issue I have. Thanks.... Keith.

  • Member since
    June, 2018
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Posted by KeithKD on Thursday, June 07, 2018 6:31 AM

Interesting, I am going through this exact thing right now. Converting most everything I have to DCC and am using TCS decoders. All my Kato Locos run just fine with the new decoders. For some reason I am not able to get the Atlas ones to run. I have a home built DCC++ basestation and am using JMRI to program and run my locos. All my Atlas locos will not run even after programming. It shows that everything took correctly with no issues. Ive noticed, as stated above this post someone mentioned that the decoders are a little thinner than the factory boards and I was not getting a good contact on the aft side of the board. Fixed that with a little bit of rolled up kapton to put slight pressure against the board contact on the frame. But still not able to run. Ive looked at those two clips you mentioned and had my suspicions about the contact of them. Your suggestion of routing those clips through the slits in the board will be my next step to try and resolve this issue I have. Thanks.... Keith.

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Posted by maxman on Thursday, June 07, 2018 2:26 PM

KeithKD
All my Atlas locos will not run even after programming. It shows that everything took correctly with no issues. Ive noticed, as stated above this post someone mentioned that the decoders are a little thinner than the factory boards and I was not getting a good contact on the aft side of the board.

Actually Jim Kelly wrote about this same subject in one of his recent MR articles.  I guess no one buys the magazine.

PED
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Posted by PED on Thursday, June 07, 2018 4:24 PM

Kieth,

To address the thin board issue, I have employed two approaches. I don't know what MR had to say about it because I do not subscribe to MR because I do N scale and MR seems to focus on HO.

One approach was to add a tiny bit of solder to the contact points. May need to file it back down a touch if you add too much.

Another approach was to insert something thin under the board to help it make contact. I have had good luck with small shrink wrap.

If I suspect the problem is poor contact, I often insert the tips of some wooden tooth picks under the board o make it tighter. That often works but is only to help trouble shoot. Need something else for a permanent fix.

Paul

Washita and Santa Fe Railroad
Circa 1970's in south central Oklahoma

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    June, 2018
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Posted by KeithKD on Sunday, June 10, 2018 10:25 AM

Hey Paul,

I had considered the small blob of solder on the contacts as well and may just be my final fix on the reinstall. Life always gets in the way of ya having fun, had not opened up my loco just yet but will post my progress.... thanks again 

Keith

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