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Surface Mount Triac for ElectroCoupler

cjackcjackOGR Forum Member DIGITAL SUBSCRIBER

I received an ES44AC this last year where the rear electrocoupler vibrated with track power turning on. At the time on mine the coupler opened and the vibrating noise only lasted a second or less. When I moved the truck, the issue went away and the coupler has worked fine. I recently encountered another late locomotive with the same symptom and found the twisted pair of electrocoupler wires on the rear truck pushed down into a very narrow space causing a wire to chafe.

On this recent engine unpinching the wire and insulating it, resulted in eliminating the vibrating noise, but the coupler is dead now. Presumably the triac or scr driving the rear coupler is bad. That engine is going back for repair.

Since I have had a similar issue and thinking ahead to have parts for when my engine is out of warranty, should the problem reoccur, does anyone know what the part number is for the triacs or scrs that operate the couplers in the newest engines on the motor drive board? I didn't note what that was when I had the chance...and don't want to open up any in-warranty engines.

Last edited by cjack
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Marty FitzhenryMarty FitzhenryOGR Forum Member MEMORIALIZED MEMBER

If it is a very recent engine, it operates from the RCMC board.  Not like the old modular board system.  If you look down on the RCMC board from the top, the F & R coupler (2 pin plug) plugs are on the upper right side of the board.  If you have the system you are talking about, your coupler is cooked from the short.   I am not a fan of how those wires are routed through the trucks.  You did well to work on them.

 

The triac you would be talking about would be from the older modular board system.  Couplers never fired from the motor driver board. 

 

What is your item number so we can confirm what board system you have.

 

 

 

 
Last edited by Marty Fitzhenry
cjackcjackOGR Forum Member DIGITAL SUBSCRIBER
Originally Posted by Marty Fitzhenry:

If it is a very recent engine, it operates from the RCMC board.  Not like the old modular board system.  If you look down on the RCMC board from the top, the F & R coupler (2 pin plug) plugs are on the lower laft side of the board.  If you have the system you are talking about, your coupler is cooked from the short.   I am not a fan of how those wires are routed through the trucks.  You did well to work on them.

 

The triac you would be talking about would be from the older modular board system.  Your couplers never fired from the motor driver board. 

 

What is your item number so we can confirm what board system you have.

The one I am concerned about is the 6-38954. I see from the picture in parts, the board is as you say. It's not broken yet but I want to stock a couple triacs in case it breaks. Since it must have had a shorted wire when I took the engine out of the box new. And my wiggling unshorted it. It looks from the picture that there may be smd triacs at the bottom right of the board. Three terminal devices. Or am I guessing wrong and the couplers are fired from one of the many leaded smd devices nearest where the plugs are?

I'm not sure how it's designed. Does the triac connect one side of the coil to common while the other lead of the coil comes from power hot?

As to the other engine which is not mine, the shorted wire has probably caused the triac to go bad. When it was shorted, it opened the coupler. So the coupler itself is ok it would seem because the shorted wire must be the one that gets connected to common by the triac and got shorted to the truck metal. Not sure how that could hurt the triac in that case except by back emf from the coupler coil. Anyway Lionel will fix that engine.

I just thought I would ask if anyone had the part number of the triacs so I didn't have to take my engine apart to find out to plan ahead For when I might need them.

Last edited by cjack
Marty FitzhenryMarty FitzhenryOGR Forum Member MEMORIALIZED MEMBER

On your engine, everything is very small the board.   The TMCC/Legacy modular board system used the triac to control features on the R2LC/R4LC boards.

 

The RCMC board system is an excellent system.  It has not been much of a problem.   Troubleshooting a bad board is not recommended.  Easy to replace.  I have worked on several hundred Lionel locomotives for Charles Ro and myself and have only seen one bad RCMC board.  I have seen many bad couplers out of the box.

Last edited by Marty Fitzhenry

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