MTH DD A40X Smoke unit question Repair broken hold down shell posts & pinched wires

Contact MTH as they have replacement posts for your repair.  I use these often.

Marty,

Thanks I will contact MTH.  Do you have any thoughts about the way the cross piece on the shell and how it comes down and pinches the wires in the third picture?

 

Mark

Was this new or an upgraded loco?

Marty,

It is used. Looks like it has had very little runtime.  No lube on the gears. I may be the first to open it up.  It had the original white battery which I have removed.  It is a 20-2178-1 Pronto 1. It appears all original no changes to pronto 1 electronics or wiring.  

I have an sd60 with same issue, are the replacements from mth universal?

The part number from MTH is FC-2000001. They are designed to fit over what is left of the original post, they have to be modified to be the same length as the original. JB Weld works the best, although the posts fit snugly. Not difficult, if I can do it. I have a couple on hand, or I can order them, they are only a couple bucks each. Cheaper than a new body shell, if you can find one. 

FWIW, I've repaired a ton of posts in various shells with brass tubing and JB-Weld.  I use the brass tubing to provide some strength, and the JB-Weld holds it all together.  I then re-drill the hole for the screw in the post.  My repairs are stronger than the original, and I haven't had to revisit any of them.

 

John,

Thanks for the idea about the brass tubing.  

 

All,

Smoke unit question on this DD A40x.  The rear smoke unit both fan and the heating element turn on or off by the rear slide switch.

The fan of the front smoke unit continues to run even when the slide switch for it is off or on.  Even if the wires for the on off slide switch are disconnected it continues to run.  The slide switch seems to only control the heating element on or off for the front smoke unit.  As you can see from the pictures this is a very different (for me at least) PS1 smoke unit.  It runs all the lighting for the front and cab of the loco.  For reference in the second pic of the bottom of the unit.  The 2 black wire coming out the board are the ones going the the front on off slider switch.  The white plug next to it to, on the left, is the constant voltage coming from the center pickup roller and ground.  Yes when you pull that plug the fan does stop.  Ok one more piece of information.  I took the screws holding the smoke unit off to get a better look.  When I lift the unit up off the metal floor of the loco the fan motor does stop and if i touch the smoke unit back down it runs again.  So I have been looking for a short but not found it.  I was wondering if one of the component on the smoke unit board is bad.  For those who will ask the rear smoke unit the wick and heating elements look brand new.  The front unit the wick was burnt really bad and hard.  So looks like this maybe something been going on for a long time.         

Mark,

I recently bought a 15 year old MTH F3 A-B-A set.  It's great!, But when I took the screws out to put in a BCR, I broke two mounting posts right where they connect to the body.  The sides did not break out so they would still take a screw.  John suggested the method he suggested to you.  Because of where they broke, I used CA, then made sure I had an easy fit of the screws buy turning them in a turn, backing back out, in two turns...and so on.  I did not over tighten by any means.  I was handling and running the F3 this week, and it held well, but I don't know if I will still have trouble if I ever take the screws out.

It sounds like that smoke unit is plugged in incorrectly, one of the connectors has to be bringing it power.  It's interesting that it's getting the ground through the chassis.  There has to be a hot wire coming in, trace it back.

 

John,

Thanks so much.  I will try to describe it the best I can.  

From the length of the wires and the color coding everything appears to be plugged into the correct connector.  From the picture below.  Top two white connectors soldered to the board.  From left to right.  White plug 1 has two black wires which go to a light board in the front by the coupler.  White Plug 2 has a black and red wire.  Black wire goes to ground and Red to Hot.  The 2 black wires soldered to board go to the slider on/off switch for the smoke unit.

In the bottom of the picture the two black connectors soldered to the board.  From left to right.  Black plug 1 has two blue wires which goes to bottom of the main circuit board.  Black Plug 2 has a black and red wire which goes to top of the main circuit board.

 

I disconnect one plug at a time.  The two black plugs had no effect to smoke unit operation.

White plug 1 which goes to the light board, (this board has its own hot and ground) had no effect on the fan when unplugged from white connector 1.  

White plug 2 when disconnected from white connector 2 turns off the fan.  With white plug 2 connected to white connector 2 and it's black wire disconnected from the other black wires tied together by yellow twist on plug, the Fan keeps running with or without smoke unit touching the chassis.  With red wire disconnected from the other red wires tied together by the yellow twist on plug kills fan.  

ok I pluged White plug 1 (the one with 2 black wires going to light board up by the coupler) into white connector 2.  Fan runs wide open with or without smoke unit touching the chassis.  Ok with White plug 2 into white connector 1 no lights or fan.

Not sure what is the next step.  Thanks.

Mark 

 

 

 

  

Are you sure the switch you think is the fwd smoke switch is not the coupler direction switch?

 

I have not worked on this engine so I can't tell you for sure what is what with out much closer pictures of the top and bottom of smoke circuit board.

 

I can tell you the double blue wire is USUALLY Always headlight.  The red and black are AC wires, or LED Marker wires.

 

Not sure why a separate plug for smoke switch.  Normally you just interrupt AC input via the switch, unless it has to do with the additional plug.  G

That wiring is sure confusing as George states, I think this is one I'd have to see in person to figure out.

GGG,

Thank you.

The coupler direction switch is on the other side and is marked with arrows going each way and I can trace the wires to the couplers.  The two switches for the front and rear smoke units are marked on and off and I can trace the wires for each to each smoke unit. (see attached pictures)

 

I took some pictures of the top and bottom of the smoke unit circuit board I hope this give you some idea.  I added them to the post and took pictures with back light to highlight circuit paths.  I hope it is clear enough.  If not I can try again.  

 

Yes MTH must of had some reason to not interrupt the AC input via the switch.  I am no expert in circuit boards or electronic components.  But I am wondering maybe if one of the components has failed and allowing constant voltage on the board overriding the switch.  In the previous post i mentioned when I lift the smoke unit housing off the chassis the fan stops running all the time and just to be clear then I can switch the slider switch on and off and it controls the fan and heating elements.

 

Any chance you can post the pictures with more resolution?  The tiny pictures make it hard to make out details.

 

John and GGG

Let's see if this bigger and clearer.  Thanks for your patience.  

 

That one is a first for me, all those spring contacts I've never seen on an MTH smoke unit before!  They obviously did this custom for some space reasons to connect to lights, etc. in the shell.  That's very odd to say the least!

 

John,

Yes MTH does get an A for creativity on this one.  The rear smoke unit is totally different then the front one as well.  Also a real piece of art

So does the fan just run or the heating element get power too?  I guess I would look at the contact pad to make sure nothing is shorted on it getting extra power into the smoke unit.

 

Some of those connectors just go to springs for the lights.

 

I hate to say it, but I would have to see it and trace it.

 

Looks like the switch interrupting a bridge to the power to the rectifier.   Normally for PS-1, no connection via the smoke unit body, so maybe a short some where on the PCB or around the screws.  

 

Is the solder joint where the switch plugs in bridged?  Is one of the resistors solder joint bridged to the smoke stack?  G

I have the PS2 version of this engine and the one time I needed to take it apart I found the spring contacts you mention, as well as the cross piece pressing on the wires. I can't say that the smoke unit boards in mine are identical to yours and being PS2 I assume they're not, but I took the whole arrangement with the spring contacts to be intended to enable the shell and the lighting installed in it to be separate from the chassis. Certainly unlike every Lionel diesel I have that giant shell lifted off entirely free of the chassis.

 

When I did this I could see that the cross piece was pressing hard on the wires but none of them was really pinched meaning insulation pierced and the wire within actually in contact with the chassis. (I could not see any point to the cross piece other than keeping that very long body shell rigid. It did not occur to me at the time to try shortening the uprights into which that piece is screwed. I was more concerned with ensuring no wires were pinned under the screw heads you can see.)

 

Maybe it's a long shot but as you mention the fan running when the base of the motor touches the chassis have you got a wire in contact with the chassis where it's been pinched by the cross piece? 

 

It's also odd that the forward unit smoke batting was charred badly while the rear unit appears unused. You mention that the forward unit switch cuts the power to the resistors - or that is how I read your comment above, which GGG has queried in his last posting - which suggests to me that unit was switched on when the engine was run but maybe no smoke fluid was in it. I can't see heat damage on either side of the smoke unit board however, but that would not necessarily mean that a circuit has not fried.

G

To answer your first question.  When the slider switch is turned on the heating element gets power when off no power.  The fan runs all the time when smoke unit is touching the chassis.  When smoke unit is lifted off the chassis and the slider switch is on off fan turns off.  If on then stays on.

I did look to see if anything is bridged.  I think you were right in the solder joint bridged where the switch is.  I hit it with an iron and removed excess.  Now neither the heating element or the fan no longer work.    

 

Hancock52

Thanks yes I would agree that maybe the last owner may have left the front unit on and that maybe the problem here.  That as G suggested something on the PCB is bad. 

 

Thanks all