Athearn Challenger (1st Run) Disasembly guide (& bulb replacement) Big Boy too?

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N Scale Athearn Challenger 4-6-6-4
FIRST RUN



Overview
The purpose of this doc is to show how to do basic disassembly of the Athearn N scale Challenger 4-6-6-4 steam loco.  While not a complete and exhaustive guide, it should do more than get you started.

This should also help with the Athearn Big Boy.
The main warning is that Athearn has made more than one run of both these locos.  So yours may have variations from mine.  Proceed cautiously.

My story
I bought a Clinchfield Challenger at a swap meet for $150- a great deal.  I enjoyed the sound decoder, and the locomotive was just fabulous.

But after about 6 months, something went horribly wrong.  A short occurred in the tender and blew out the original MRC sound decoder.  Being an adventurous guy, I removed the decoder and proceeded to hotwire the loco to run under analog.  This was a simply matter of jumpering the track wires to the motor wires.

But I made a newbie level error.  I totally forgot about the tiny incandescent bulb.  The decoder probably only provided 5 volts to the lamp circuit.  When I exceeded that, the tiny incandescent bulb blew.  Doh!

So now I have a loco with a dead sound decoder and a blow bulb.  It ran fine under analog, but a lot of the fun was gone.

I decided to change the bulb out- but had no idea how to proceed.  I searched the net for instructions and found none beyond how to simply get the shell off.

So with much fear and trembling I set out to disassemble the loco.  This guide is thus my gift to you to get you started on disassembling and repairing yours.  Sorry my photos are very poor.  I did not start out with printing an article in mind.  I simply wanted to document any tricky steps for myself so I could get the thing back together!  But these photos, poor as they are, should be enough to help you.

A whole lot more to come...........

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To take shell off loco

remove little cap in front of cab.   Easy to lose!)






Remove the screw that was hidden under that cap. 

Remove screw in the stack. 




Pull cab handrail wire over brace below cab. Shell now just slides off.

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To take shell off tender (you do not need to remove the rear coupler):

(sorry no photos)

1   Remove two screws from back behind ladders on bottom of tender.
2   Remove the coal.  Stick a tiny screwdriver in back of the coal and lift edge.
3   With coal removed, now you can see a screw under where coal was.  Remove.
4   Remove rear water hatch from the roof.
5   Now you can see rear screw to remove.
6   Lift the rear of the body slightly.  Then pull out the back wall.  Important: there are some latches on the side of the main body that retain the rear end panel.  Lifting the shell slightly moves them out of the way so the rear end panel can be removed.
7   The tender Body shell should now slide off toward the rear.

To get to the pickups, you need to remove all the weights.  The rear weight just slides up off the post.

The front weight is harder.   There is a screw under the speaker that holds the sound box/weight.  Speaker must be removed.  Remove the two screws and retaining washers.  If not removed before, then you will probably find the speaker glued in place.  Use small screwdrivers to carefully lift it up.

Now you can see the screw at the bottom of the weight/sound box.

The loco came with what I think was a poor decoder.   There were two plugs which plugged into the decoder.  One plug obviously goes to the speaker.

The other plug goes from the decoder to the main loco.
That plug is organized:  outer wires are track power (red and black), the next inward is motor power (orange and gray) and the inner wire is negative to the front headlight (white wire).

I made a silver mark at red- so you can see the chart below to figure the rest out.

Since each outer pair goes together, you could jumper 1&2  and 4&5 for analog operation. 
Remember- if you run it now, this will blow the headlight possibly (which is what I did).

I eventually installed a ESU LokSound.  I'll show that later toward the end.

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Tender wires coming into loco up to the loco circuit board.




Cab area
L       black wire no paint.     LEFT rail.
M1       white painted wire        MOTOR 1  TOP pole
Lamp    green painted wire         one side of the headlight
M2       yellow painted wire      MOTOR 2   BOTTOM pole
R       red painted wire      RIGHT rail.




Motor section
M1 red wire top motor pole
M2 black wire bottom motor pole




Trucks sections
P3. Right side rear truck
P4 left side rear truck
P1 right side front truck
P2 left side front truck.





Lamp. Both black.

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You will probably want to remove the front pilot truck.

Remove the screw.






Here is the order when time to reassemble.

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In order to do much, you will almost certainly need to remove the circuit board.

Unsolder all the wires.  In case I ever removed the motor, notice I marked it for TOP.



Here is my circuit board.  It may or may not match yours.
Top side.




And bottom side.   
NOTICE:  the headlight traces run along the bottom to the circles in the back (and up to the top side).  Since I need to replace my bulb with an LED, I needed to know this.




The first run board with an incandescent bulb has diode protection for the bulb and to make it directional.   Since an LED is a diode, I didn't need them any more. so I removed the barrel shaped diodes.




Now, I needed to add a resistor so I will not blow out my LED.
There is a tiny trace that runs from Diode 1 to the middle pad of Diode 2.


I cut that trace because that's where my resistor will go.






So now, with this mod, my LAMP pads are LAMP in the 5 pads at the end D1.   If blue and white function wires are attached there, the LED will operate.

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I'll add more later. 
Must stop for now.

next will be removal of a engine power assembly.

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To Remove the engines from the loco.

(don't lose any parts!  Work with LOTS of clean elbow room.)

1  Remove shell. (covered above)
   Screw in stack
   screw hidden under cap in front of cab
   move cab handrails over the bar at bottom

2  Remove circuit board (covered above)
   unsolder wires
   remove board

3  Remove front engine

On top of the main piston, there is a pipe that comes in and is retained by a pin.   VERY carefully lift hinge tubing so that pin comes up (right on top of the cylinder).






Now Remove the worm cover up top.
Stick a tiny screwdriver in truck electrical tab (outside edge- see red lines) and pry outward to release locking tabs on the worm cover.  Repeat on the other side.  It is a bit tricky since the side you released locks back.





Now remove worm and universals from down in the geartower.






Straighten the wires to bulb and carefully slide the whole assembly down and away from the chassis.

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Front engine and truck disassembly

1  Remove the pilot truck (described above).
   Remove the screw. 
   Note the curve slot for screw.  Peak of slot forward.
   When reassembling, Spring goes up against bottom of loco, then the washer, then the truck.

2  The pivoting pipe needs to be removed.  Pins can be pinched from underside to remove.



(You are entering tricky territory.  Things fall apart. )


3  Remove the air pumps from the sides under the steps.  Each has two pins-- just pull each outward.



Note- The air pumps are the only thing that directly holds the step assembly-- well, except the bulb wires.

4  Remove the screw on top side of the power cylinders and slide the cylinders forward. 



Watch for the two metal rods.  They pull out easily.
The curvy part goes toward the drivers.  There is a little hole/slot for it in the plastic.



NOW we are getting close to the bulb wires.



5  The headlight/number board piece comes right up.  Just pull. (Yellow)

WARNING- THIS is the step where things fall apart......

6  Remove the screw behind the gear tower (red).  Just know that the delicate side rod stuff is now loose! Can be tricky to get it all back.

BUT!  Now the plastic plate can be lifted  (blue) and you can get to the bulb and bulb wires.   The bulb wires run under that plate.





You might want to put that screw  (red) back in there before it all falls apart.

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What I did at this point was to pull the incandescent bulb out and went to replace it with an LED.



So I wired an LED (pre wired is good too!)  Do NOT worry about polarity right now.






LED is to the left.  Run magnet wires UP through the hole as shown.




Now put the cover plate back in place.  You might need to loosen that infamous screw on back of the geartower.



The install the main pistons.

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I positioned my LED about where I wanted it.



I then took the walkway/pilot piece and opened up the hole on the bottom a little.




Then slid it over the LED and into place.




Pushed the air pumps in place.




And put the headlight in place.



Before I can install the curvy steam pipe, I have to move my wires out of the way.



Pipe installed from up top.

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BEFORE we put it all back together, I test fit some very thin/small heat shrink tubing into the hole for headlight wires.



It needs to go all the way through and extend from the bottom to the top.



I then position it so that it will stick out only a little at the bottom.





Now ready to install the engine back into the chassis.
There are two holes- one on either side of the boiler screw.
Run the LED wires through the rear hole up to the top of the loco.



As you put the engine in place, the curvy steam pipe must go into the hole in front of the screw.
You can see the LED wires also- don't pinch or scratch them.




Almost there.



Install the worm.



Slide the wires into the worm cover.



Snap the cover in place.




And then put the pins back into the main pistons with their piping.

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Install the circuit board in place.



Solder all wires back except the LED wires.




Now, if you are thinking that the wire is VERY exposed, you are correct.  We need to fix that.



I placed thin heat shrink tubing on a drill bit.



And heated it to shrink  it.



It this then slid down the LED wires and into the hole.   If I measured well earlier, then it will only stick up a little.



I can then trim solder the LED wires to the board.   The wires must have some length so they can flex when the engine pivots.

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The last step for me was to run a jumper wire back to the decoder in the tender.

This will be the blue wire (goes to the resistor).   Wire soldered to resistor, goes under the board....



I removed the pony truck and loosened the screw that holds the wire bundle.




And then ran the magnet wire into the tender for the decoder.



 

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And that concludes this section.

I know this won't apply to everybody, but I hope it helps someone.

This is a very complex locomotive.