Runaway TMCC Soo Line SD40

Hi Rod.  I see you haven't received a reply.  I am probably not the right person to provide advice on TMCC, but I'm wondering if perhaps there is a bad connection on one of the boards.

I helped a friend with a TMCC engine once, and somewhere on the forum I had found someone who said sometimes you just need to separate the boards and reset them.  My memory has faded, but I think it suggested that with time the boards just need to be separated and put back together a couple times to remove any corrosion.

Also I had something similar with a Legacy engine and recalled this post from sometime ago  https://ogrforum.com/topic/168388668001090171.  I know its Legacy, but I guess its the same concept as having a bad connection.

Hope that helps, or better yet maybe the heavy hitters with more knowledge will help you out (and not be too hard on me for my lack of knowledge )

Rod - I would think the likes of @harmonyards and/or @gunrunnerjohn might have some suggestions on how your problem may be able to be resolved, so hopefully they or some other techies will chime in with some ideas. Good Luck!

Check for a loose magnet ring Rod, …..sometimes they get hung up enough to work, then work themselves loose again, and that sends the system into a hissy ….could be other issues, sensor, or driver, but top suspect would be the magnet ring,….

Pat

The first step would be the actual Lionel product number so we can see exactly what we're dealing with.

@gunrunnerjohn posted:

The first step would be the actual Lionel product number so we can see exactly what we're dealing with.

We are away a few days so I don’t have the product number real handy, but the road number is 6622 and its from about 2001 or 2002 era.

Pat I recall other posts where the magnet ring can be a problem. Once we get back home I will pop the shell and check that out. Thanks!

Rod

If it has Odyssey, the magnet ring is #1 on the problem list!  However, usually a power cycle doesn't fix it, so I'd be thinking maybe the Odyssey driver as well.

@gunrunnerjohn posted:

If it has Odyssey, the magnet ring is #1 on the problem list!  However, usually a power cycle doesn't fix it, so I'd be thinking maybe the Odyssey driver as well.

It does have Odyssey so I’ll check the magnet ring and go from there. Might get lucky! Trouble is you have to run it a while to see if anything changed, and vigilence is needed to make sure it doesn’t hit the cement gorge!

That's what makes me think it might not be the magnet ring.  Another thing to check is if the flywheel is loose on the motor shaft, I've seen that a few times as well.  Also, the connection between the motor sensor board and the DCDS could have a break in the wiring.

Thanks for those thoughts John. There’s a few things to check when she’s on the workbench.

This is one of a few engines that spend about 99.9% of their time sitting dormant on a whisker track. And you kind of forget the little idiosyncracies of each until you run it again. It occurs to me that this runaway mostly, if not always, happens in the same section of the layout. I am wondering if because of its specific roller spacing there might be a fraction of a second power loss causing the problem? Would that throw Odyssey into the twilight zone?

Rod

I see there is one listed on ebay as item # 6-28523 from 2001. Price is $360. That’s the one.

if it is occurring on the same section of track, check to make sure you have connectivity between each set of rollers, the track is clean and that the antenna is properly seated to the board.

Marty

@gunrunnerjohn posted:

That's what makes me think it might not be the magnet ring.  Another thing to check is if the flywheel is loose on the motor shaft, I've seen that a few times as well.  Also, the connection between the motor sensor board and the DCDS could have a break in the wiring.

I’ve seen that too John, …..good catch!…

Pat

Well we made some progress on this issue today. The magnet ring seems fine, flywheel is tight, nothing else obvious. Checked roller connectivity and bingo, front roller on the front truck is dead. There is 4 total rollers; two each truck. Without a connection from the front roller there is only 9-1/4" spacing from the next roller to the rearmost roller; which can be a little tight for this layout. Sure enough found a disconnected red power wire where it should make connection at the top of the truck. So at least we know the problem. Now how to get the truck off to get to where the repair is needed?

Glad to hear you found the problem!  Hopefully it can be fixed in a way that it doesn't happen again, maybe a slightly longer wire, maybe shrink tubing over the wire if it's rubbing on something or ream out what it's rubbing on and coat with liquid electrical tape, etc.   Good Luck!

Not sure exactly how a bad roller connection results in a runaway...

@gunrunnerjohn posted:

Not sure exactly how a bad roller connection results in a runaway...

Not sure it does. But it is one identifiable problem that needs addressing. It may or may not be the root cause of the runaways.

Rod

@Rod Stewart posted:

So at least we know the problem. Now how to get the truck off to get to where the repair is needed?

From the description, my assumption is this is the Lionel 6-28523 Soo Line TMCC SD40-2.

Let the games begin!   You have one of the infamous Lionel Puzzle Trucks!  They're not like most trucks, you need to disassemble the truck in order to remove it from the chassis.

The good news is, if it's truly just the pickup wire, you should be able to access that screw through the slot in the chassis and fix it without removing the truck.

Yes it appears to be this truck:

Would anyone have a blow-up drawing of this guy perchance? I am hoping as John said to be able to replace the power wire without major surgery, but who knows!

Rod

Rod,

Check your email, sent you a diagram that may help.

Good Luck,

Tom

Tom many thanks; that is the exact truck. Should be an easy fix now, just need to get some free time!

Rod

Like I said Rod, if you're just replacing the collector wire, I don't think you need to drop the truck.

UPDATE: Got the truck hot wire fixed with minimal fuss. John you were right, no need to drop the truck to get at it. Tom thanks for that truck blowup you sent me. That is the correct truck even though it indicates it is for the U30C series engines.

I attach an excerpt from the truck assembly drawing below.

The power wire solders to an extension of spring #15, which sticks up through thimble #17. This is a loose fit in the truck and retained by plate #18. To disassemble it you must first remove the roller retainer screw #46 from the bottom, which screws into spring #15. The spring and thimble can then be removed from the top through a crescent shaped hole in the baseplate. The problem appears to be that the shrink sleeve protecting the solder joint to the spring had not been shrunk, thus the wire twisted with every turn of the truck, and eventually fatigued and broke free.

She's back on the layout and ran for about half hour tonight with no recurrence of the runaway problem. so I am thinking this was the issue all along and occasionally produced just enough of a power hiccup to cause Odyssey to go berzerk and run away. Time will tell if this is correct. Keeping my fingers crossed.

Many thanks to all who contributed ideas and suggestions!

Rod

Aren't you glad you didn't have to take that truck all apart!   Those are fun to get all the axle bushings lined up with the flats in the right place to get them back together!

@gunrunnerjohn posted:

Aren't you glad you didn't have to take that truck all apart!   Those are fun to get all the axle bushings lined up with the flats in the right place to get them back together!

You can't imagine my joy! So it looks like plate #6 is the carrier for the front 2 axles, and #7 is the carrier for the rear axle. And it appears they both remove from below, which is handy. But it looks like the D plate #21 (where the motor mounts) is all one piece with the worm driven gear shaft #27 carrier. So does this have to come off the main truck frame #1 before you can drop the truck out of the frame? And it looks like that's the only way to get to the worm gear for greasing, since the motor is attached from below the D plate. Did I get that about right?

Ran it again today for about a half hour and all is well. No runaways, at least so far!

Rod

I sort of follow my nose, but I know you end up with a lot of screws and parts before you can totally remove the motor!