Unreliable Electrocoupler

This is usually mechanical issues, even though you can't find anything apparently wrong with the coupler.

Try this simple test. Unplug the coupler from the board and run the train and see if you still have the issue of uncoupling.

Do a search on this you will find the reason to do the test John has recommended. There is an internal spring that holds the plunger against the knuckle to keep it closed. The coil actually compress the spring to allow the knuckle to open. If the spring is shortened or weak, the plunger opens. G

Hi Kanawha,

I had the same problem. It was very frustrating. Here is a Link to my thread for this issues. When all was said and done I ended up replacing the entire truck on a brand new engine, which of course came with a new electrocoupler.

Good luck.

It may not require that extreme a measure, this should be a pretty simple fix. In any case, electrocouplers are pretty cheap if he can't fix that one.

OK, I unplugged the electrocoupler (Duh - why didn't I think of that?) and ran the engine at varying speeds for about a half an hour. It did not uncouple by itself once. Looks like I will try the capacitor. Thanks for the info on the size. By the way the engine has a TAS EOB board in it. Does anyone know of any issues using the cap with an EOB board?

Ken

No issue with their board. I think the old site recommended twisting the leads together from the coupler to help eliminate any noise triggering the coupler. Does your motor have capacitors on the brushes? G

Wires from the board to the electrocoupler are twisted. Motor is a pretty common Mabuchi can motor so it does not have caps. Another piece of info - The coupler that's giving me the problem is a replacement. The original coupler never gave me a problem until one day it stopped working because one of the wires to it broke where it goes into the top of the coupler. I wonder if some couplers are more sensitive to electrical "noise" than others?

Ken

quote:

By the way the engine has a TAS EOB board in it. Does anyone know of any issues using the cap with an EOB board?

No problems. And yes, some individual couplers are more sensitive to electrical noise than others.

I'd twist the wires, and put the cap across the coupler. Also, I'd put a 1uF 50V NP cap across the motor brushes as well, that's another source of noise that may be part of the issue.

He said the wires are twisted and the motor is DC

For some couplers, if you remove the insulation on your old coupler you can unwrap the wire/resolder to the wire then heat shrink a cover or use good electrical tape. G

quote:

Originally posted by GGG:
He said the wires are twisted and the motor is DC

For some couplers, if you remove the insulation on your old coupler you can unwrap the wire/resolder to the wire then heat shrink a cover or use good electrical tape. G

The motor being DC is still a problem, it's the brush noise that causes the issues. My suggesting still applies. BTW, some of my Lionel TMCC locomotives with DC motors have these caps from the factory.

Well, I'm hope I'm not speaking too soon, but I installed the cap across the electrocoupler leads and it seems to have cured the problem. Thanks for the help guys.

Ken

Hope that does the trick.

quote:

Originally posted by gunrunnerjohn:
The motor being DC is still a problem, it's the brush noise that causes the issues. My suggesting still applies. BTW, some of my Lionel TMCC locomotives with DC motors have these caps from the factory.

John, I do not believe this is true. AC motor generate much more noise than DC. Those DC motors that have capacitors have been to supress noise for circuit issues such as speed control and chuff.

To get the coil coupler to electrically open, you either need a noise signal that the command board reads as fire the coupler command, or generate sufficient magnetic field to generate a current in the coupler wire.

Most fixes I have seen for the coupler are the capacitor or a resistor in the coupler wiring.

I also believe these still have a basic mechanical issue. Either spring tension is too weak, or spring length too short, that a miniscule current generated in the coil allows the plunger to move slightly and release the knuckle. I venture to say, stretching the spring, so a fully engergized coil is required to move the plunger would solve most if not all issues, other than noise commanding a coupler firing via the circuit board. G

I agree that AC motors generate more noise, but to think that the sparks you see on the brushes of a DC motor aren't resulting in any electrical noise is to ignore the obvious. I also agree that the cap across the coupler is probably the first course of action. However, if that doesn't do it, and it's an electrical issue, I'd still try the caps across the motor brushes.

Clearly, as was demonstrated in the other thread, there are mechanical issues with some electrocouplers as well.

It is a theory that can't be proved or disproved So we can load up the engines with extra diodes, capacitors and resistors to fix them. Hey maybe we can pull the lead weights with all that extra electronics!

Actuually, I will try to measure the voltage/current necessary to trigger a coupler. I still have a hard time believing noise is generating enough EMF to pull the plunger unless the plunger is mechanically weak, either by spring tension or length or both. But hey, it is only my theory G

quote:

I still have a hard time believing noise is generating enough EMF to pull the plunger unless the plunger is mechanically weak, either by spring tension or length or both.

You can choose to believe it or not, but I've repaired about a dozen locomotives that had sporadic coupler openings using the capacitor fix. In every case, those couplers ceased opening on their own and operated as designed from the Cab-1. Absolutely nothing mechanical was done to any of them.

quote:

Originally posted by GGG:
I still have a hard time believing noise is generating enough EMF to pull the plunger unless the plunger is mechanically weak, either by spring tension or length or both. But hey, it is only my theory G

What makes you think the noisy motor can only affect the coupler directly? EMI can affect the circuit that fires the coupler, a lot more likely scenario.

quote:

Originally posted by gunrunnerjohn:

quote:

Originally posted by GGG:

What makes you think the noisy motor can only affect the coupler directly? EMI can affect the circuit that fires the coupler, a lot more likely scenario.

I don't, as I stated above the other alternative is commanding an uncoupling. But if that happens how does the capacitor on the coupler block the command firing? G

quote:

Originally posted by Bob:

quote:

I still have a hard time believing noise is generating enough EMF to pull the plunger unless the plunger is mechanically weak, either by spring tension or length or both.

You can choose to believe it or not, but I've repaired about a dozen locomotives that had sporadic coupler openings using the capacitor fix. In every case, those couplers ceased opening on their own and operated as designed from the Cab-1. Absolutely nothing mechanical was done to any of them.

Bob, I never questioned that the capacitor doesn't work. How do you know if you had replaced or stretched the spring instead, that it would have solved it too without the capacitor?

I have only had to fix 2 couplers. I stretched the spring and that solved both. I never have added capacitors to any couplers, but my sample size is small.

I guess the circuit could be momentarily signalling the coupler to fire with out activating Railsounds, but I believe the coupler is sensitive since it is not standard practice that all TMCC engines have capacitors installed on the coupler. So either the R2LC is more sensitive in a specific engine, or it is the coupler that is too sensitive; if electrical noise is activating a coupler with just momentary current, the other solution could be a stiffer spring that requires more force to open. Which means a longer timed current pulse. Something sporadic noise is less likely to do.G

quote:

but I believe the coupler is sensitive since it is not standard practice that all TMCC engines have capacitors installed on the coupler.

Talk to Mike Reagan or Jon Z sometime. Capacitors are built into all Legacy boards now.

Legacy yes but Jon posted in a different thread that using capacitors on the couplers with the new electronic boards being used would damage the boards. G

FWIW, I have a number of locomotives that have caps across the couplers, both of the K-Line TMCC ones have them from the factory. I also have several that have caps across the motors, also from the factory.

John, I am sure there are. Seems the newer stuff has been more suceptable to issues for all manufactures, while some of the early designs seem more hardy. Will be interesting to see how the new Lio electronics work.

Read this thread completely.

Coupler problem

So after Lionel installs the capacitor fix it still would not work. He then stretched the plunger spring and it seems to work.

This issue to me is similiar to the misbehaving R2LC that people fix via elaborate ground plan wiring. Yes, some layouts require it, but there are also those R2LC with faulty sensitivity. Replace the R2LC and the engine runs fine again on the original wiring. G

I have read the coupler thread. I don't argue that some of it is mechanical, I've certainly had my issues with some of the Lionel couplers. However, I also don't discount other causes when mechanics don't explain the issue.

I had an Katy SD-70 from the 2nd run that had couplers that fired randomly. One thing I noticed was that if the car coupled to the engine had a plastic knuckle, the random firing stopped.

The loco was replaced because the sound failed and the replacement loco has not exhibited the random firing

Almost sounds like a short of the windings to the frame in the coupler, very odd.

quote:

Originally posted by gunrunnerjohn:
I have read the coupler thread. I don't argue that some of it is mechanical, I've certainly had my issues with some of the Lionel couplers. However, I also don't discount other causes when mechanics don't explain the issue.

Sure they do John. It wouldn't surprise me that these faulty couplers are opening with 5 to 10ma vice 50-100ma. Tolerances of the bore, plunger and spring can all be aligned to have the plunger move soon as the first electron enters the stream! All I am saying is make sure the coupler needs a strong current to open as the first fix. What I usually do is tap the coupler to see how easy it opens with a jolt. G

 

How do I remove the plunger on the coil coupler so I can stretch the spring.

Do i need to remove the knuckle to access the plunger?

Yes, you need to remove the rivet holding knuckle, then the plunger and spring can come out. G

Of course, you need a new rivet to replace the one you removed.  For some, it's easier to spend the $10 for a new coupler.

 

I agree, I have had good luck with Lionel rivets.  MTH not so much.  The coupler is more brittle.  Of course I have not seen many weak couplers with MTH.  G

 Usually a cap will fix the random firing of a coupler. If its a mechanical problem, don't stretch the spring, that's not the fault. The fault is with the knuckle, take a file and true the area where the plunger locks the knuckle. I use a miniature square file and take 3-4 strokes and its square. When you assemble the coupler you can feel the difference when the pin locks.

 

  This also works on thumb tack couplers. Where the pin locks the knuckle you can file that area and get more of a positive lock. Give it a try.

 

Bill