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New Conversion of N Gauge Life-Like SW9-1200: December 5, 2006

Posted by on Jan 16, 2014 in Locomotives, Tony's Tips | 1 comment

Fred writes :

“This new style of digital conversion for the N gauge LL SW9-1200 was emailed to me and I thought that you might be interested in this new approach which allows you to keep the weight of the loco.

You may get some innovative ideas for the decoder placement and the LAD improvements. As to the improvements on the gearing and pickups, that may not be relevant to what you are offering your clients.”

(The following was written by Bill Hebb)

A few folks have asked about the N gauge LL SW9-1200 conversion with both forward headlight and cab headlight while keeping the full cab weight. I have posted some pictures of that conversion in the group photo directory. In the pictures where the shell is off, the very small yellow square is the surface mount LED.



It is an N gauge LifeLike SW1200, re-motored with an Atlas slow speed motor, NWSL low profile nickel silver wheels and a Digitrax DZ143 installed where the original headlight board used to be. The original factory plastic worm gears are replaced with KATO brass worms for quieter running. Note, that unlike some conversions posted on the internet, I have left full supporting posts on both sides of the plastic motor cradle and the full cab weight is retained.



The DZ 143 has had the factory plastic cover removed (note this violates the Digitrax warranty) and uses a surface mount LED on top of the decoder for the front headlight with a resistor soldered directly to the DZ143 where the white wire was originally placed. The LEDs and mini resistors are from Jim Hinds at Richmond Controls. The cab light is also a surface mount LED, nestled in a groove in the cab weight. Note the vertical groove is offset from the center so that the wires are hidden behind the cab vertical mullion.

Front headlight and cab headlight, full cab weight, excellent DZ143, in summary I am very pleased with the conversion.



The pickups are indeed a weakness of this engine from more than one perspective. First, they are poorly mounted and often break off. Second, they are prone to being bent, even from the factory and significantly changing the chassis ride height, which causes an entire spectrum of motor worm gear to truck top gear issues. I kept the original pickups but have bent them so that they project downward from the walkways no further than the jacking pads under the walkway. Then I bend an angle in the very end of the pickup that puts it parallel to the track. This limited pickup height ensures that the pickups make constant contact with trucks, while keeping the trucks riding on the frame and not being “sprung” down by the pickups. The pickups being bent incorrectly from the factory or by handling are usually the cause of the bouncing, gear noise, gear mesh problems with these engines.



Once the trucks run at a constant height, than you can adjust the motor worm gear to obtain an optimum mesh. I usually do that by using .010 x .010 or .020 shims just under the motor bearing saddle and the plastic motor cradle, this raises the motor vertically .010 or .020 higher and all the gear noise is gone. If a thicker shim is needed to reduce the sound, take a very close look at the frame and see if it is not bent up at the end in relation to the middle. I have fixed several friends SW1200s that would not respond to shimming by judiciously bending the frame ends straight again- it is relatively soft and prone to being bent out of shape in many directions.

Because there are many slightly bent frames and bent pickups out there, all the different “solutions” to the gear mesh problems may work on some engines but not on others. I always check the frames first and go from there.



The resistors are 1/8 watt, 1.5k.  I am more than willing to share anything with fellow modelers who might be interested in the installation. But frankly, I believe it might be just a bit beyond beginning modelers. First, the outer cover of the DZ143 must be removed, the circuit board trimmed slightly at the four corners to remove small projections, and finally three wires must be de-soldered from the board, and a resistor soldered to the board.

Once you remove the Digitrax red plastic cover, the decoder wires have a tendency to come unsoldered real quick. I hesitate to recommend to beginning modelers to start soldering around a decoder.  As you well know, once the cover is off, the Digitrax warranty is history, and you need a small watt iron, with a very fine tip and a good eye to perform the soldering.



In summary, as far as the front light goes, here is how I did it.  Unsolder the white wire from the DZ143. For the purposes of this explanation, the bottom of the decoder has the wires soldered to it; the LED will lie on the top of the decoder.

Take one of the resistors and bend its lead in a u-shape, be careful with the bend not to crack the resistor casing.  The purpose of the U bend is to allow the resistor lead to be soldered to the decoder where the white wire used to be, then immediately bend 90s towards the top of the decoder, and then bend 90 degrees again so that the resistor lays on the decoder with the other lead point to where the LED will be. Squeeze a 1/16 of the resistor lead to flatten it to make it easier to solder to the decoder. Just lay it on the decoder for the next step. Take a piece of small wire (such as 24-28 gauge, strip the insulation off, and keep the insulation.



Take the surface mount LED from Jim and lay it on top the decoder. Put the LED itself at the leading edge of the largest chip at the most forward part of the board.  You can see that chip in the pictures. Now, see how long the wire from the LED needs to be to connect and solder to the lead of the resistor pointing forward. You have to eyeball that Herb. What are you going to do with the insulation? Cut it to the same length as the chip is wide so that the two wires from the LED will be insulated inside the insulation as they lay on the chip. The attached pictures will clarify this.

Trim the forward lead of the resistor to as short as you are comfortable with to facilitate soldering to the (-) wire of the LED. Trim the (+) wire of the LED the same length.  Thread both LED wires thru the insulation. Solder an approx. two inch piece of decoder wire to the (+) LED wire, sold the (-) wire to the forward lead of the resistor and you now have a unit that includes, resistor, LED and a length of wire. Now you can solder the U shaped lead of the resistor to the decoder.

The wire soldered to the (+) lead of the LED can be joined with the decoder blue common light wire at a location of your choice. I used the back at I also needed to join to the rear LED (+) lead and had the most room at the back in front of the weight.

    1 Comment

  1. It is April 19, 2018. I went Kato in Schaumburg to buy 4 sets of N scale E-unit brass worm gears per the article for my 4 Lifelike N Scale SW switcher models. I have changed the first unit’s worm gears and the difference is amazing. Now the little switcher sounds just like a quiet Kato model. The brass Kato worms are a direct replacement (once you press them off their shafts) for the stock Lifelike plastic worms. SO, Northwest Shortline stopped making their #2675-6 Lifelike wheelsets years ago, they told me. Any idea where I might still find a set or two? DesPlaines Hobby definitely does not have them.

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