Motor replacement for 1997 Atlas GP 40-2

[DWS3]

Gents,

After having issues with three decoders on my Atlas n-scale GP 40-2, I am starting to think the issue may be a faulty motor.

Here is my question (more background info below): Can the newer Atlas AF670L motors (https://shop.atlasrr.com/p-56627-n-motor.aspx) be easily retrofitted into a 1997 vintage locomotive ( https://www.spookshow.net/loco/atlasgp3840.html )? The loco in question is marked "Atlas 1997" on the side of the frame and was sold as DCC ready with the split frame. It currently has the original motor which is pretty much all black...I think a "high speed motor?" I contacted Atlas about an original replacement and they said they are no longer available. They also said the newer motors would not directly fit and I should try searching the internet (which came up empty). If it will fit, is there anything else I would need to do other than adjust the plastic motor mount to fit the metal engine frame?

Here is the background/history. I bought the engine back around 2000 and put a drop-in Digitrax DCC decoder in it. Over the next 25 years, the engine ran fine but infrequently due to many military moves. Recently I retired from the military and started running trains again. This engine was sporadic at best, even after a thorough cleaning and light lubrication. After 15-20 minutes of running, it finally just quit running and my NCE Powerhouse DCC system wouldn't even recognize the decoder anymore.

I bought and installed a brand new ESU LokPilot drop-in decoder which turned out to be a fairly loose fit. The DCC system would never recognize it, even after I tried hard wiring between the various pads, motor, and track pickups. After getting nowhere, I bought a TCS M1 decoder and hardwired it in. Initially is seemed to work and I was able to get it to run back and forth on a test track, however the speed was too high. I put it back on the programming track to make adjustments and the DCC system would no longer recognize there was a decoder installed. I sent the decoder back to TCS and they said it was shorted and are sending a new one. Since I pretty much covered the entire engine frame and decoder in kapton tape and was extremely cautious, I find it very hard to believe the motor or decoder made any contact with the frame or anything else that could short them out.

The engine ran perfectly on DC using the original light board and a transformer, tested before and after each decoder install. Since I have now gone through three decoders, the only thing I can think of is there is something internally wrong with the motor that is burning out decoders but still allowing it to run on DC. I really don't want to keep throwing money at the engine but I would like to see it run again, as I have a second GP 40-2 to consist it with. I believe the 670L motor referenced above is the newer "low speed" motor but that would be fine since I am basically using the engine as a yard switcher.

Also, I have tried programming several other engines on the NCE system and they work fine, so I'm sure the DCC system is not the issue.

Thanks!

D.W.

[peteski]

D.W., do you have any idea of roughly how many hours of running are on that motor?  I'm asking because in general those motors have very simple construction and are very reliable. Also, if it still runs well on DC, then that also seems to confirm that the motor is ok.  While there is a possibility that there is something odd going on with the motor, the odds are pretty low.  Plus most decoders have the motor output protected from shorts.

If the motor has high milage then the carbon dust from the brushes could have built up on the commutator gap causing excessive current consumption. But that should not cause decoder damage.  Seems more likely that there is a short somewhere to the chassis (yes, I know you covered all with Kapton tape).  Interesting problem . . .

[DWS3]

Peteski,

I’d estimate 10 hours at most.

D.W.

[peteski]

Peteski,

I’d estimate 10 hours at most.

D.W.

I was thinking more like hundred hours for the motor to start getting worn out. 10 hours would be like new.

[peteski]

Is this the chassis?



The plug-n-play decoders often have problem with reliable contact with both, the frame halves, and motor contacts.  But the hardwired one should have reliable connection with the motor (soldered?).  How are you connecting the wired decoder track power wires with the frame halves?

[tehachapifan]

If the motor leads make contact with the frame anywhere, that will likely result in a decoder-killing short. This kind of short rarely often does not manifests itself in anything of concern when operating with an analog light board. That's how motors used to get power pre-DCC (off the frame).

[DWS3]

Is this the chassis?



The plug-n-play decoders often have problem with reliable contact with both, the frame halves, and motor contacts.  But the hardwired one should have reliable connection with the motor (soldered?).  How are you connecting the wired decoder track power wires with the frame halves?

Yep, that's the one, although the grey/white plastic part of the motor is black on mine. I soldered the track power wires to the top of the respective brass strips that run between the trucks, right above the fuel tank. The motor wires were soldered directly to the brass motor tabs.

Unfortunately, the site will not let me upload pictures.

D.W.

[mu26aeh]

Unfortunately, the site will not let me upload pictures.

D.W.

Get above 25 posts and you'll unlock that feature.  Keeps spammers at bay

[NtheBasement]

There are motor issues and there are decoder issues.  What you describe (can't recognize the decoder) is a decoder issue.  I can't imagine how that can possibly be fixed by a new motor any more than repainting the shell would fix it.  Focus on the decoder-frame electrical contacts.  Try dielectric grease ($1 at your local auto parts).

[John]

Yep, that's the one, although the grey/white plastic part of the motor is black on mine. I soldered the track power wires to the top of the respective brass strips that run between the trucks, right above the fuel tank. The motor wires were soldered directly to the brass motor tabs.

Unfortunately, the site will not let me upload pictures.

D.W.

If you are blowing up decoders, it's quite possible that there is a short somewhere on your frame .. send me your pictures, and I will post them for you ..

[DWS3]

Get above 25 posts and you'll unlock that feature.  Keeps spammers at bay

I figured it was something like that. Guess I need to spend more time here!

D.W.

[DWS3]

[ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ]

If you are blowing up decoders, it's quite possible that there is a short somewhere on your frame .. send me your pictures, and I will post them for you ..

Pictures sent. Of note, the pictures were taken after the LEDs and much of the kapton tape was removed so I could show TCS the connections.

Thanks!

D.W.

[DWS3]

There are motor issues and there are decoder issues.  What you describe (can't recognize the decoder) is a decoder issue.  I can't imagine how that can possibly be fixed by a new motor any more than repainting the shell would fix it.  Focus on the decoder-frame electrical contacts.  Try dielectric grease ($1 at your local auto parts).

Are you saying I should use a little dielectric grease at the electrical contact points, such as between the trucks and brass strips for better electrical flow? All other connections were soldered together.

D.W.

[peteski]

If the model works fine in DC, the track pickup is fine. I would  not add dielectric grease. That stuff is thick and insulating. While it is good for keeping moisture out of stationary connections (like in a light bulb socket), in contacts which constantly move I would not use any grease - maybe very light coating of light oil. Personally I prefer to polish the contact areas to mirror-like finish. The metal polish will protect the surface from oxidizing.  But I don't think that's the problem here.

To be honest, the wiring is a bit of a rat's nest (probably just for troubleshooting?) and I also see a small board with black and blue wires (not currently hooked up). Is that some sort of keep-alive circuit?  I would make sure the model runs well before attempting to connect  it.  Actually this type of circuit might cause problem with programming decoders on the programming track.

Do you recall if the DC mode is enabled in CV29 (it usually is by default if you didn't modify it).  Use a fresh 9V battery and touch it to the chassis halves to see if the decoder will run the motor.  Don't try the DC power pack - those often don't work well with decoders.

I'll also send you a PM.

[DWS3]

If the model works fine in DC, the track pickup is fine. I would  not add dielectric grease. That stuff is thick and insulating. While it is good for keeping moisture out of stationary connections (like in a light bulb socket), in contacts which constantly move I would not use any grease - maybe very light coating of light oil. Personally I prefer to polish the contact areas to mirror-like finish. The metal polish will protect the surface from oxidizing.  But I don't think that's the problem here.

To be honest, the wiring is a bit of a rat's nest (probably just for troubleshooting?) and I also see a small board with black and blue wires (not currently hooked up). Is that some sort of keep-alive circuit?  I would make sure the model runs well before attempting to connect  it.  Actually this type of circuit might cause problem with programming decoders on the programming track.

Do you recall if the DC mode is enabled in CV29 (it usually is by default if you didn't modify it).  Use a fresh 9V battery and touch it to the chassis halves to see if the decoder will run the motor.  Don't try the DC power pack - those often don't work well with decoders.

I'll also send you a PM.

The small device ahead of the decoder is a TCS KA-N1 keep alive https://www.tcsdcc.com/product-page/ka-n1 It was never actually wired to the decoder, as I planned to add it after making sure everything else was good and the programming was complete.

All the wires were neatly folded and taped down after initial installation. I agree they did become a bit of a rats nest after pulling the tape off. Next time I'll probably just cut the wires shorter but still with a bit of slack.

Not sure what CV29 was programmed to but I never intentionally changed it. In fact I never really got beyond setting the decoder to a 4-digit address before the problems arose. The next planned step was adjusting the speed tables when the system stopped recognizing the decoder. I've never used the transformer based power pack for anything but testing of DC engines before DCC conversion. It isn't even in the same room as the layout. Once the decoder is installed, I only run them on the DCC powered track.

Thanks for all the help!

D.W.