Need Help With Digitrax DH163AT Decoder Installation in Athearn F-7

[BradKT]

As I have been building my layout, it has been a while since I got on this board...so I extend a belated Merry Xmas and Happy New Year to everyone.  The layout is pretty large with a lot of scenery...a Northern California industrial park is the setting with oil refinery complex (tank farm, natural gas loading facility and truck loading facility), fire house, rail yard, construction equipment rental company, truck-rail terminal, station, bus stand, gas station, wharehouse and cement plant.  I plan to take pics and post them soon.

I have had no problem installing my Digitrax 165AO DCC decoders in my Atlas engines...piece of cake!

I had set the Athearns aside until now so I tried to install 1 of my DH163AT decoders in an new Athearn RTR F-7.  I checked to see if it ran before I started.  This is what I did:

1.  I got the shell and weight off and took the engine out.  I used double electrical tape over the shiny copper part on the frame under the engine.  If I had put electrical tape under the entire bottom of the motor, it would have blocked the four holes where the plastic motor mounts plug in to re-seat the motor.  I replaced the 4 mounting screws and the original motor mounts with the screw holes with the plastic motor mounts (which do not use screws) that came with the decoder.

Question - Did I properly isolate the motor?

2.  I plugged in the decoder to the harness.

3.  I got the top and bottom motor clips off (and kept the springs in) and replaced them with the motor clips (attached to the gray wire on the bottom and the orange wire on the top). 

4.  I re-seated the engine, taking care to re-align the drive system.

5.  I plugged in the red wire to the front and rear truck posts.

THAT WAS THE EASY PART.  AFTER THAT THE PROBLEM BEGAN...

6.  The instructions say that the black wire should be clipped to the headlight post at the front of the frame but it doesn't say how to do this and I have no clue!  What do I do?  At present, the black wire is not hooked up.

7.  The instructions show the violet (F-2) wire and the green (F-1) wire, but don't say anything about where they go.  Are they supposed to be hooked up?  How?

8.  Do I leave the headlight in?  Do I take it out (including the clip)?

9.  What do I do with the yellow, white and blue wires?  I am leaning toward not hooking up any lights.  The Athearn F-7s have no rear light anyway.

10.  I put the engine on the track and while the headlight lit up, nothing else happened.  When I tried to program it, the light went off and then came back on after I had completed the programming process.  The engine does not run.

Question:  Have I ruined it or is my work just incomplete?  I need someone to walk me through this. 

Help!

[pdlethbridge]

Black and orange to the motor. Okay. Red to trucks, Okay. Black to frame anywhere. Think about this, the red and black go to track.  The white and blue (common) to front light . Yellow and blue ( common ) to back light. Don't worry about any other wires on your decoder for and athearn unit. As long as the motor is isolated from the frame and the orange is on one brush and the gray on the other brush, you should toast the decoder. Just tap a hole in the frame somewhere and attach the black wire. If you use a 12v bulb for the front light, like a model power bulb, use a 100 ohm resistor in series to give you a less bright bulb, and longer lasting bulb

[BradKT]

Thank you.   One last question.  Do I need to lose the front light bulb that came with the Athearn engine?  I remember seeing somewhere that I should.  Can you tell me if that is true and why?

[pdlethbridge]

I am not sure, but I like to put in my own bulbs because they are easier to wire. Athearn bulbs have no wires.

[Jim Banner]

I assume pdlethbridge meant to say the grey and orange wires to the motor.  The black wire needs to connect to the locomotive frame.  The easiest place to make this connection is at the bracket that holds the headlight bulb.  If there is an "S" clip on the black wire, use that.  Otherwise solder the black wire to the bracket.  Don't like soldering?  Then strip about 3/4" of insulation off the end of the black wire and jam the bare wire between the bracket and the frame.  Easiest way to do that is to grasp the wire at the very end of the stripped part with one hand and hold it farther back with the other hand.  Then work the bare part in between the bracket and the frame just as if you were flossing teeth with it.

How did the headlight light when you were testing the decoder?  The base of the bulb has two contacts - the outer metal shell and the solder dot on the end of the base.  The metal shell is held against the mounting bracket by a black plastic clip.  This clip also holds a bronze leaf spring that normally touches the metal contact sticking up from the front truck.  I am assuming this bronze spring is still in place and that is how the solder dot was connected up to make the bulb light.

If you want to control the headlight with DCC, you must cut the bronze leaf spring to about 1/4" long so it is well clear of the front truck contact.  Then you can solder the white wire to the stub end of the spring or directly to the solder dot on the bulb.  Or you can strip about 1/4" of insulation off the end of the white wire and jam it between the bronze spring and the black plastic clip.  Just make sure in either case that the white wire does not touch any part of the headlight bulb bracket or the metal shell of the headlight bulb base.  Do not connect the blue wire to anything!  This type of wiring is known a half wave lighting, and it works best if you do not run analogue locomotives on your layout.

Alternately, you can replace the headlight bulb.  My favorite for F units is a 5 mm warm white LED installed right in the headlight hole in the shell (you may have to ream it slightly.)  With an LED, you must use a resistor in series with one of the leads (it doen't matter which one.)  If you look carefully at the LED, it will have a small rim around the end next to the wire leads.  Next to one of these leads, the rim has a flat spot.  This is the negative connection.  This lead is usually shorter than the other lead, which is the positive lead.  The positive lead connects to the decoder blue wire.  The negative lead connects to the decoder white wire.  One of these wire must have a resistor cut into it somewhere between the decoder and the LED.  Try 10,000 ohms as a starting value.  If this is too dim for your liking, try half the resistance, or the standard value closest to half the resistance.  You can try lower and lower resistances until you reach a brightness you like, but do not use less than 270 ohm.  At 270 ohms, the warm white LEDs that I use are blindingly bright and 5100 ohms is about right, but your results may vary.

Those left over wires (yellow, green and violet) plus the two solder pads on the decoder can be used for other light functions, for example, MARS light, cab light, marker lights and/or ditch lights (the latter takes two function outputs if you want them to flash alternately.)  If your F-unit has two headlights, you might consider using one as a regular headlight and the other as a MARS light if your railroad used them in the era you model.  Some users use function outputs to control smoke generators, couplers, and even to make the engineer look forward or backward depending on the direction his steam locomotive is moving.  Beyond that, the only limits on uses of function outputs are those imposed by your imagination and technical skills.

[BradKT]

Thank you both.  You have completely answered my questions. 

[pdlethbridge]

Yes, gray and orange to motor...WHAT WAS i THINKING!!!!!

[BradKT]

I am sorry to say that things have not worked out.  I followed all of the steps that you said:

1.  I took the engine out and covered the shiny part under the motor with 2 layers of electrical tape;

2.  I removed the old clips (and didn't lose the springs) and attached the clips on the decoder harness (clip with grey wire on botton and clip with orange wire on top);

3.  I attached the red wire to the front and rear truck posts (plug-ins)

4.  I drilled a hole in the side frame, put in a screw and I soldered the black wire to it and tightened it to the frame with the screw.

5.  Attached decoder.  Two decoders have already gone up in smoke. 

After all that, I tried a second engine...and a 3rd decoder.  The headlight comes on and then goes out during the programming sequence...and then comes back on after the sequence is completed.  Nothing else happens.  The engine doesn't move.  This is the second of 2 brand new Athearn RTR F-7s.

Athearns are a major pain (you know where) and I am on the verge of giving up.  Is there a short somewhere?  Why am I thinking that it has to do with the headlight?  Somehing is getting juice or the headlight wouldn't be coming on.  What am I doing wrong?

I need some more help.  This is getting extremely frustrating.

I did not attach any of the other wires to anything.

Finally, if I can't do it, where can I get this done professionally?  I live in the Los Angeles, California area.

[pdlethbridge]

try your local hobby shop.

[Jim Banner]

Brad, learning by burning up decoders is an expensive way to learn.  So lets see if we can figure out what went wrong before you lose another one.  There are several steps to installing decoders that you have not mentioned having done.  So lets discuss them first.

Any locomotive that you buy, either new or used, may have problems.  If you are going to install a decoder, test it first.  This is rule One - do not install a decoder in any locomotive until you are satisfied that it runs properly on dc. 

The first step in installing a decoder is to check that the motor current is within the capabilities of the decoder.  Normally, a brand new locomotive does not draw more current than the decoder designed for it.  But once in a while a motor draws more current than it is supposed to.  It can still work fine on dc but unless you check it with a meter you will never know about the problem until you smoke a decoder.  So Rule Two - always check the motor stall current before installing any decoder

When you install a decoder, you absolutely must isolate the inputs (the black and red wires) from the outputs (all the other wires.)  Failure to do so will usually destroy the decoder.  First, hook up just red, black, orange and grey wires.  Use tape to make sure there are no obvious short circuit paths.  If you must connect wires together, solder them and insulate the joints with shrink tubing. Do not connect any other wires at this time.  Use an ohm meter to check the resistance from each of the above four wires to the other three.  That means a total of 12 resistance checks.   If you cannot touch the meter probe to the end of a wire (such as at the strip under your Athearn motor) then use a sharp pin to puncture the insulation somewhere along the wire and measure to that.  If you have any doubt whatsoever about the pin touching the wire inside the insulation, put two pins in that wire about an inch apart and make sure there is a low resistance between them.  Then you know for sure that both are touching the wire inside.  This is Rule Three - be sure the inputs and outputs are isolated from each other by testing with an ohm meter.

You can now test the installation.  Just make sure that none of the other wires can touch anything (tape over their ends if need be) and that no part of the decoder touches anything metal (like the frame or the truck connections.)  You might even want to mount the decoder at this time, usually using double sided foam tape.  Installing the shell is optional at this point.  Call this Rule Four - test the basic installation before connecting the functions.

After successful completion of the above test, you can connect up lighting and other functions.  If you are using existing headlight bulbs, make sure of three things - that they are the correct voltage, that they will not get too hot, and that they are not connected to anything else.  The exception to the latter is half wave lighting as explained in an earlier post.  If in doubt, install your own bulbs, or better yet, use LEDs along with an appropriate resistor.  Rule Five - all function wiring MUST be isolated from the red and black wires and from anything connected to them.

Over the years, I have done trouble shooting on a number of locomotives that  people have unsuccessfully tried to install decoders in.  Almost all of them have involved breaking one or more of the rules above.  A few have had motors with shorted turns in their armatures.  This made them draw excessive current but still allowed them to run on dc.  Some have had decoders that may have been faulty from the get go, which has led me to test all decoders on receipt.  But most of the problems have involved errant connections between the decoder input and the output, and most of those were because the motor was not properly isolated.  On Athearn locomotives, this often involves the ground tab on the bottom motor clip poking through the tape used to isolate this clip.  I avoid this by switching the top and bottom clips.  The DH163AT decoder avoids the problem by giving you new clips.  Some other causes include the decoder shrink wrap being punctured by truck tower connections because the decoders were left unmounted and got pinched when the shell was reinstalled.  Then there was one case where the owner carefully isolated the bottom motor clip from the frame but then connected the top motor clip to the wheels by reinstalling the springy metal strip that normally connects the top motor clip to the two trucks and the light when the locomotive is used on dc.  If Rule Three had been applied in these cases, the decoders would not have been destroyed.  And lastly, there have been "bird nest" problems, particularly with F-units.  It seems that all that room gets people thinking that there is lots of room for wire, so they just ball it up and cram it in, hoping that none of it will snag the flywheels, drive shafts, gears, etc.  Of course, it does just that, and drags the motor to a dead stop.  Then I have a happy customer - no charge for a new decoder and no charge for a few minutes spent tying the bird nest into a manageable bundle with a bit of dental floss.  I included that as a reminder that not all cases are doom and gloom.   

[pdlethbridge]

Check out Digitrax new guarantee. You may be able to get a new decoder or 2.

[Jim Banner]

Unfortunately, the new warranty covers defects in manufacture but specifically excludes damages caused by failure to isolate the outputs from the inputs.

quote:
This warranty specifically excludes damage due to customer abuse, such as ...  failure to properly protect against over current by properly isolating the locomotive motor from the frame when installing mobile decoders.

[BradKT]

The engines that I have tried this on run fine...they are Athearn RTRs straight out of the box and run fine on DC.  I think that the problem may be somewhere in the process you describe as step 3...the red, black, orange and grey wires.

I have been trying to think this through logically and my thinking is that the problem is somewhere in the middle of what I am fixing to describe:  When it comes to isolating the motor, do I need to do anything more than just cover the shiny strip under the motor with a couple of layers of electrical tape...I think that the engine itself still makes contact with the metal frame when I re-seat it.

Question:  Now this is the one thing that I didn't check...should the bottom clip (with the gray wire attached) make any contact with the frame itself?  I am reasonably sure that it still does because I only covered the shiny part on the bottom of the frame under the motor (the rectangular area where the copper is that is touched by the motor contacts) with electrical tape.  Should I make sure that the entire length of the bottom clip does not make any contact with the frame?  The reason that I ask this is because the black wire is connected to the frame via screw and solder and the red wire that plugs into the truck leads would logically make contact with the frame via the current going through the light bulb that makes contact with the frame.  That could mean that the gray, black and red wires are all touching the frame.  I am just thinking out loud here because I am sure that it is something simple that I am missing.  Is the motor properly isolated if the clip and grey wire are still touching the frame? 

The light bulb is coming on when I put the engine on the track.  That means that current is coming from the track through the truck leads and along the long clip to the light bulb and should logically be going to the motor as well through the motor clips with the gray and orange wires...am I correct that the long clip that came with the engine and goes on top of the top motor clip to make contact with the trucks is supposed to be re-installed?  The more that I think about this, the more I have some doubts about re-installing that long clip...

[Jim Banner]

That could mean that the gray, black and red wires are all touching the frame.

Black wire touches the frame - that is okay, it is supposed to.
Red wire touches the frame through the headlight bulb (but no direct connection between the red wire and the frame) - that is okay too.
Grey wire touches the frame - that is NOT okay.  It means that one output wire (the grey one) is connecting directly to one input wire (the black one.)

Is the motor properly isolated if the clip and grey wire are still touching the frame?

No.  This is a direct short circuit between the grey wire and the black wire via the frame.  Isolated means No Electrical Contact.  Insulated would be another way of saying the same thing.

The light bulb is coming on when I put the engine on the track.

This means the light bulb is connected via its mounting bracket to the frame and via the bronze strip to the front truck.  This is fine as long as nothing else is connected to the front truck besides the bronze strip and the red decoder wire.  The light bulb in the path between the red wire and the black wire is no problem.  Only a direct connection ("short circuit") between the red and black wires would cause a problem, but not for the decoder.  Such a connection would short out the tracks.  Follow the current path - from one rail to the wheels to the truck frame to the locomotive frame then somehow over to the post on the truck and from there to the wheels on the other side and to the other rail.

Normally, using tape to cover just the shiny groove under the motor is enough.  But in some cases the bottom clip or its wire still manages to touch the metal chassis.  Using the ohms function of a low cost digital multi-meter will pick this up very quickly.  Such a meter costs about 1/4 of what a DH163AT decoder costs.  Personally, I cannot imagine installing decoders without one

[BradKT]

You know, the more that I think about this, the more that I think that I maybe I shouldn't have reinstalled the long clip.  After all, the plugs on the red wires run from the truck posts through the decoder...but the long clip makes contact directly from the top motor clip (with the orange wire) to both truck posts without going through the decoder.

Does anyone have any thoughts about this?  Could the solution to the problem be this simple?  In other words, the motor is properly isolated...it's not the gray wire making contact with the frame...it's the ORANGE wire connected to the top motor clip which is making contact with the truck posts via the reinstalled long clip.

And yes, I did see the transformer's short circuit signal come on...