View Full Version : Insulating the motor for DCC decoder

15th Jun 2015, 10:33 AM
I understand it is always advised to isolate/insulate the motor from all else when installing a DCC decoder. Has anyone advice on the best way to do this? How exactly it is done? With What materials?
I imagine there are a few variations on how to do this depending on the type of motor, how and where it is mounted and whether it is DCC ready or not.
Here is a list of the n scale locomotives I plan to convert:
At least 3 of these have the motor and pickup on the tender so if there is no space anywhere I will mount decoder and speaker in car behind.
Bachmann American 4-4-0.
Atlas Mogul 2-6-0
Arnold 2546 KBAY P42 4-4-0
Fleischmann piccolo 7159 4-6-0
Kato 2007-2 C57 4-6-2
Bachmann Spectrum B&O EM-1 w/DCC - Baltimore & Ohio #7614 2-8-8-4

15th Jun 2015, 01:40 PM
greetings, trainstrainstrains, and welcome!

I am not in any stretch a DCC knowledgeable guy, only what I have read here.
At the very least the motor must be isolated/insulated from the frame
and what I hear most using is called Kapton tape, which is a thin but very
insulating kind of tape.
Google is or search for it on amazon dot com

Others who are more knowledgeable will certainly chime in.
But the need for Kapton tape is pretty much a necessity.

sincerely, fwiw...

15th Jun 2015, 02:54 PM

The motor needs to be isolated so that the inputs from the dcc decoder are the only electrical inputs going to the motor. If you fail to isolate it, you could fry your decoder.

Now to isolate the motor, you need to disconnect anything that can carry a current from the track from the motor inputs. And then connect the decoder motor outputs onto those same spots. Since a bunch of n scale locomotives utilize a split frame to transfer the power from the wheels to the motor, you will need to make sure that those frames do not come in contact with the motor inputs via a barrier. The barrier that people tend to use is kapton tape (very thin and stops an electrical current), but you could use anything that is non conductive. I know there are people who use the nonconductive paint. Others is bigger scales will use electrical tape. The downfall to electrical tape is that it can leave a residue and has issues with a buildup of heat. Kapton tape is thermally resistant as well.

Now ow to get kapton tape, you can just search for it. I bought 100 feet of it for less than $5 on eBay, but you will only need it in small amounts. Digitrax in their decoder packages tend to include a small portion of kapton tape. The tape is yellowish in color and is usually holding the decoder onto the foam piece or on the instruction manual. I can try and take a picture later so that you can identify it.


15th Jun 2015, 04:30 PM
I almost ordered it but I thought I'd ask first. Shall I buy the 5, 10 or 20mm width kapton tape?

Another somewhat related question. Where to find super miniature connectors? In the instances where I choose to place the decoder in a car behind the tender, it would be nice to be able to disconnect it. For this not to look absurd the connectors would have to be just wider than the wires, about 1 to 2 mm.

15th Jun 2015, 06:48 PM
I bought 20mm by accident. I find that it is too wide. If I was to buy it again, I would order a narrower width. I can't tell you which would be better. I'd say take a look at how wide your motor contacts are since that is what you need to cover up.

For the connectors, I've seen a package from TCS that sells some. Also TwinDad has mentioned before that there is another company that sells connectors of all types. Digikey.com But you'd have to ask him for ideas on which ones would work best. (I'll watch for what he recommends so that I can purchase the same thing.


15th Jun 2015, 09:24 PM
DigiKey has a lot of stuff on it, but finding what you need is not necessarily easy. Plus, often especially the small connectors require specialized tools to assemble.

If it were me, I'd go for the TCS micro connectors. I used the minis on a steam loco install not long ago, and they worked pretty well. The micros should be even better. Plus they are pre-assembled.

15th Jun 2015, 09:41 PM
A couple of SoundTraxx products to consider DBX-9000 loco to tender wiring kit and 810058 mini-micro connectors of the two the 810058 is much cheaper.

15th Jun 2015, 09:53 PM
I almost ordered it but I thought I'd ask first. Shall I buy the 5, 10 or 20mm width kapton tape?
The kapton tape that I get with Digitrax decoders is 10mm wide.

16th Jun 2015, 05:18 PM
I've order Capton tape 10 mm from ebay.
1 two pin TCS micro connector cost about $10 from TCS, I'm sure they are perfect but that must be 10x what they should cost. 1 four pin TSC micro connector from ebay costs $11.95 that's a bit better but still too much. Did not find two pin TCS m. c . on ebay. Soundtraxx {810058} MICRO-MINI CONNECTORS (PACK OF 10). $8.95 free shipping on ebay , that's reasonable I'll have to go with that, I hope they don't look too big.
Thanks everyone.

20th Jun 2015, 10:53 AM
It looks this will not be easy either.
Motor chassis is metal , screws that attach motor to tender chassis are metal and tender chassis is metal.
How then is it possible to insulate the motor? The only way I can think is to replace the screws with plastic screws and place capton tape between tender chassis and motor. But plastic screws that tiny size? Probably don't exist and would not be strong.
Looking closely at the motor frame I see that the outer u shaped shell is metal but in that there is a dark brown body that is not metal and not conductive, this gives me hope. I have written to Fleischmann, let's wait and see if they have anything encouraging to say.

20th Jun 2015, 02:01 PM
You don't have to insulate the motor frame. Only the connections to the brushes.

20th Jun 2015, 11:02 PM
If I don't have to insulate the motor frame then all I have to do is disconnect the motor, connect the two wires from the track directly to the assigned wires on the decoder, connect the motor exclusively to the decoder, disconnect the light and connect it to the assigned wires on the decoder making sure nothing is grounded. Correct? Might not even need the Compton tape?

20th Jun 2015, 11:10 PM
Possibly. Lots of older locomotives would use the metal frame to carry the current from the track to the motor.

Some models are easier than others. have you tried looking on spookshow's website? He has a bunch of models reviewed and discusses if they are dcc ready. I use it when purchasing a new loco, but if you already have them on hand it should be easy to open them up and look.


21st Jun 2015, 08:25 AM
Could you show us some pictures?
It's much easier if we can point at things.

21st Jun 2015, 08:32 AM
I am familiar with spookshow website and refer to it often, in it he admits not having much on european models and asks for people to contribute which I did by sending him photos and a PDF from Fleischmann on my loco which is most definitely not DCC ready, I have taken it apart completely and have studied the PDF, Track power is picked up from all locomotives wheels only, from there it goes directly to the front light and directly to the motor, there is no other wiring, it is rather simple and straightforward. All 8 tender wheels are drivers , no drivers in the loco, the motor and gearing are also in the tender.
If the motor is easy the only challenge will be keeping the light in the same place without it being directly connected to the track because It's support is a flat metal plate that becomes the pickup on one side of the track. I think I'll manage that. There is absolutely no room for anything more either in the loco or the tender so the decoder will have to go in a car behind.
I think the only thing missing once the Compton tape arrives is super super thin gauge wire. Anyone know a good place to buy this and what it is called ?

21st Jun 2015, 08:38 AM
I have yet not managed to upload anything to this page, I am trying to upload a PDF and photos right now. What is max resolution?

21st Jun 2015, 09:34 AM
Don't know really.
What I do is upload pictures to the "My Gallery" section here on the site. From there you can insert BBcode directly to your posts.
The pics shouldn't be more than 1000 pixels wide. I keep mine at 800 pixels on the longest edge.

21st Jun 2015, 10:16 AM
I just keep making the picture smaller until it uploads.

21st Jun 2015, 10:33 AM
Tiered of trying to upload so here is a temporary link to flikr https://flic.kr/p/uGkQdk

21st Jun 2015, 10:45 AM
Okay, for DCC you need to get rid of the small capacitor and the choke coil. They're the two components mounted at the rear. Once they're gone, you should have room for a decoder there.
I can't see how the motor is wired. Can you show us a picture from the rear, so we can see the connections to the motor?

21st Jun 2015, 10:50 AM
Here's how one guy DDC'd the 7159 on a Bulgarian site (http://railwaymodellingclub.com/?cid=57&NewsId=60).

21st Jun 2015, 01:28 PM
Great link, I must study it carefully, Iím afraid my Soundtrax decoder with sound is a little bigger , I donít mind having it on a car behind with micro connectors so I can disconnect the car, Iíve done the same in large scale. Iíve posted more photos as requested; they are next to the first one. I see the loco and tender on the Bulgarian page are basically the same as mine.

The PDFshows everything but I would need an email to send it. Since the Bulgarian page shows everything including the connection to the front light no PDF is needed?

Two questions: 1 In the Bulgarian page I see only one wire going to the light? 2 In the Bulgarian page there is an extra grey cable from the motor that goes nowhere?

21st Jun 2015, 01:38 PM
Very nice steampower4ever videos.

21st Jun 2015, 02:46 PM
No need for the PDF.

I can't say what the grey wire is for, but here is the basic wiring diagram for most decoders. This is from an ESU LokPilot manual and there may be differences from decoder to decoder, but it does show the basics. You need to study the manual for your decoder.
The task for any DCC conversion is to figure out how to get the connections in place without any two being shorted. That differs a lot from model to model, and you need to use your multimeter to figure out what's connected to what on your locomotive. Especially the frame is used for a common ground on older models.



21st Jun 2015, 05:59 PM
Rather straight forward, the blue being the ground, in my case probably to the frame. Correct?

21st Jun 2015, 07:29 PM
You can use the frame for it, yes, if that is most convenient. Just make sure that all other connections are isolated from the frame.
I am currently doing a conversion (http://www.nscale.net/forums/showthread.php?37819-Kato-GS-4-with-ESU-LokPilot-micro-DCC-v4-decoder&p=433731#post433731) on a locomotive with a design that has fried more than one decoder before it was fixed from the factory.

In the case of ESU above, the blue is actually not ground. You should rather think of it as a common signal for the outputs.
When the bulbs are on, the yellow and white have a lower voltage than the blue. Bulbs don't care about the direction of the current of course, but if you switch to LEDs, they must be connected upside down in the schematic above.

Your decoder may be differently wired or color coded, but the basic principle should be the same.


21st Jun 2015, 08:14 PM
In the Bulgarian site notice that the white wire is used for headlight, that is the function output wire from decoder the circuit is completed with track pickup from left rail. Because it is a bulb this will work. Track power is DCC and swaps phase similar to AC so the bulb does not care. the extra wire you noticed is a yellow wire for a future back-up light. If you ever use a LED the blue wire supplies positive voltage .