Athearn Big Boy issues

[UP Simon]

My Athearn Big Boy has never run properly.
Stops and starts all the time over track that my Challenger runs over fine.
My thinking is that the pickups and wheels in the tender are the issue.
In order to test I’m thinking of swapping the tender from the Challenger as it’s perfect.
Has anyone swapped the tenders and is it possible?
ie are the plugs the same and position of the various feeds in the plugs the same?
Thanks for any advice/support

[peteski]

I have both models (with Tsunami decoders, not the 1st run with MRC). In mine, the tenders and connector pinouts are electrically identical.  And yes, the electric pickup can be hit-or-miss in these.

All loco's drivers are designed for picking up power, but each model uses different design.  Big Boy has wheel-back wipers, which are often not adjusted properly to contact the wheel.  Challenger's pick up driver's power through the axle bearings.

In the tender, all but the rearmost wheelset should pick up power, but often that is not the case.  The pivoting front truck is designed like Kato passenger trucks (axle-point and bearing-cup pickups), but in mine (from the 2nd run) the wheels were insulated from the half-axles, making the truck electrically dead!!  I noticed that friend's Big Boy (from the later run) had wheelsets which were designed properly.

The 5-axle "centipede" part of the tender is supposed to pick up power through wheel-back wipers on the 4 forward wheelsets. Rear one is s electrically dead by design.  The electric wipers can often be incorrect adjusted, so they don't pick up power.

Tender swap is possible, but a *MAJOR* pain in the a$$!!  Not recommended!  The only realistic way to do it is on the locomotive end (and the wires have to be desoldered from the PC board in the loco.  The loco's trailing truck and some parts of the frame also has to be removed.This loco is not designed for easy disassembly. Just the opposite.

Better news is that the pickup problems I mentioned above can be resolved without any major disassembly.

First of all, figure out which wheelsets (drivers and tender) are electrically dead. Make sure that DC operation is enabled in decoder's CV29 (it is by default), then place the model upside down in a cradle (or figure out how  to hold the model upside down without damaging any details).  Then take a fresh 9V battery and touch it to every driver and all but the rear tender wheelset.  If you hear the decoder start making sounds, the pickup is ok (9V is not enough for the motor to run, but that's ok).

Once you figure out which sets of pickups need to be adjusted properly, you can address the problem.

On the loco's engines, the pickups are attached to the bottom gear case cover. It can be removed to adjust the wipers without needing to touch the drivers or valve gear. But since there are wires from the cover running up into the loco, you can't fully remove the cover. You just have to separate it from the gear case enough to be able to bend the pickups out so they touch the drivers' backs. Then you need to put the gear case cover back on, making sure the pickup wipers stay properly aligned.

In the tender, if the front truck is dead electrically, get replacement wheelsets from Athearn. I just did that for mine.  They cost $5 per pair. 
in the centipede part of the tender the wipers can be adjusted by removing the 5-axle "sideframe" and removing the wheelsets.

To remove that sideframe you have to remove the 4 screws in its center line, 2 screws at the back corners, and the coupler with screw also have to be removed (this is a but of a pain due to the uncoupling level  being in the way, and the coupler box halves not being welded together. Then pull the sideframe up, starting at the rear, then the front of it will have to be coaxed out carefully to clear the front truck.

Once the sideframe is removed, the wheelsets just pull out, allowing the access to the pickup wipers. This is a good time to clean all the wheel treads with alcohol.  Next, adjust the wipers, and reinstall the wheelsets (it is a bit tricky to do and keep the wipers from being bent incorrectly again).  As you put each wheelset back in, get the wiper aligned on one side, then tilt the wheelset slightly to get the other wiper properly located. And when you're doigin it you have to make sure the other, previously installed axles do not come out.

Once you do this, use the 9V battery to test each wheelset's pickup. If all is good, the model should run very well.  If you are not up to this challenge, contact Athearn customer support to see if  they would do this for you.  In my experience, they are very nice and easy to deal with.

[superchief]

i bought 3 of these 1 for my nephew and one for me, one ran well the other not, got one more and had the same problem. I did the same thing and isolated the pick ups. I ran my engine up on a paper towel with the tender on the track and the loco ran. put the tender on the paper towel and the loco on the track would not run. bad contacts on the engine. I also own the 1st run of the challenger and big boy (with MRC) both run flawlessly on the layout. I contacted Horizon/ Athearn and sent the loco back with my notes, the loco was return and they found no problems!!!! I ran the it on the layout and it was worst! I believe the contacts are pushed down in transport, I pulled the bottom driver cover partially as there are wires attached and carefully with a very small thin screwdriver and pried the contacts outward and the engine runs well now!!!! Gordon
 

[UP Simon]

Thanks Peteski, followed your post with 9 volt battery.
Tender pickups are fine, all the Drivers are electrically dead.
Attempting to remedy now by pushing the contacts out to contact the wheel backs
Let you know how it goes

[propmeup1]

Both big boys run fine but both challengers do the same thing as yours.  All four are the early ones with MRC decoders.    BTW the BLI Y6B pull twice what an Athearn big boy can and without slowing down on my 1.34 %.

[TVRR]

I'm currently having an issue with my 1st run Challenger. The front engine is not receiving power, everything else is as it should be. A look at Spookshow's site has me pretty well convinced that this is going to need more expertise than I have. If I'm looking at it right, the shell comes off and you are confronted with 2 circuit boards , one that has to be removed to get at the drive gear. From there I'm lost.
Anyone with the expertise that would like to make some money, I'd like to hear from you. Thanks, Pete

[NDave]

It's really not too difficult to move the PCB out of the way to access the drive train. This might help: https://www.nscale.net/forums/showthread.php?47379-Replacing-motor-in-my-N-scale-Athearn-Challenger-(2017-release)

After you access the drive train, you can check to see whether the front drive joint has become disengaged, loose, or?

[TVRR]

Dave, Thank you for your clear and concise explanation, with pictures no less. I had read this a while back and forgot where the thread was. It has all the info I need, now just have to work up the nerve, I guess.

[UP Simon]

So followed Peteski’s advice as none of the pickups on the drivers were contacting the backs of the wheels.
Pushed them up against the wheels and just like magic I have a functional Big Boy.
Thanks very much team!

[peteski]

So followed Peteski’s advice as none of the pickups on the drivers were contacting the backs of the wheels.
Pushed them up against the wheels and just like magic I have a functional Big Boy.
Thanks very much team!

Excellent!  Thanks for following up.