MTH ABA Trailing unit failure?

Please provided MTH model #'s.  If they are RailKing sets, they will be 30-xxxx-1.  If they are Premier, 20-xxxx-1.

They are Premier 20-2306-1 Southern Pacific and Premeir 20-2346-1 Western Pacific.

Okay, thanks.  Both of those are PS2 5v.  Have you replaced the batteries with new batteries (or BCRs)?  I'm not saying that's the source of your problem but you should do that before you run the engines.

Yes that is the first thing I did!

And they are both the BCR..

That's good to hear they both have BCR's.  I have a three different MTH tethered ABA units.  I haven't had any problems so I'm not sure where you should start.  Be patient and someone should chime in.

Thanks! Maybe tomorrow I will post some accident scenes where these failures have happened on my lay out! This is my first experience with tethered units but my other MTH loco's run just fine on this same layout. Thanks again!

Here are some pics of where 2 different Premier ABA units failed. All this is 031 curves. I think the tethers force the trucks to derail. Am I the only one who's experienced this? The last pic shows a derailment. Does anyone know if this is the correct number for a replacement motor FET on the slave boards PS2 5v :IRLR024NTRPBF

if the number your showing was on the fet yes, it is correct. I can repair the board for you If you would like to have fet's in stock, here is the part number

!IRLR024NTRPBF Infineon Technologies | Discrete Semiconductor Products | DigiKey

p.s. if you have derailments you WILL DAMAGE the electronics   slave board and ps 2 boards can also be damaged 5 volt or 3 volt boards !

Alan

Thanks Alan!  You are absolutely correct on the derailment statement! I just don't know what is causing it. All my other locomotives run perfectly only the two tethered ones derail and not all the time..... so I guess I was thinking the 031 curve is just too tight....? As long as I don't put the trailing A unit on the lead A and B run fine. I will most likely take you up on your repair offer... unless I just pull the motors out and drag them around as "dummys"!!!

I have an MTH A-B-A set and found that the tether from the B unit was clamped very short and lifting the back truck of the first A unit up in tight turns. There was plenty of slack inside of the B unit so I just loosened the clamp and pulled between 1/8 and 3/16 of an inch of the tether out and it fixed the problem. Maybe yours has the same issue.

Others may differ, but my experience with manufacturer's minimum diameters (both of your engines are rated for O-31 curves) is that they're referencing a nice, smooth (in this case, O-31) full curve. From your pic's, it looks like you have a few sharp S-curves of O-31 diameter and that may put it in a different perspective.   

Thanks for the reply, I thought about that too...but they surely seemed long enough perhaps I will just unclamp them and leave them loose and see what happens... I am also going to put a torpedo level in different places on my layout to see if I got bumps or something on the track that I can't see. I attached a picture of the tethers of both my trailing A units ...just to see...? The earlier post with the pictures the 4th one shows the trailing unit derailed. Thanks!!!

Yes I agree with Richie.. the S curve needs to go...

another thing that can cause derailment are the wheel flange are too high which causes the wheel to push up as the wheel crosses over switches and derail you can easily fix this by using a Dremel to grind down some of the plastic in the frog switch area!

Alan

I just looked at that area and it definitely pushes the wheel up. I am using 031 switches and they have a grounding buss running on top of that area. Can I just eliminate that piece and then grind the area down? My O72's don't have that ground buss....  Also the O31's  are in a auto reversing loop if that would matter.. Thanks, Bill

@Alan Mancus posted:

if the number your showing was on the fet yes, it is correct. I can repair the board for you If you would like to have fet's in stock, here is the part number

!IRLR024NTRPBF Infineon Technologies | Discrete Semiconductor Products | DigiKey

p.s. if you have derailments you WILL DAMAGE the electronics   slave board and ps 2 boards can also be damaged 5 volt or 3 volt boards !

Alan

I would like to get this fixed would you need the whole locomotive or just the board? I will perhaps contact you through email. Thanks, Billl

The board can be fixed, and needs to be modified if early version, you also need to ensure the motors, and trucks are clean and properly lubricated and spin freely. No hang ups.  Also can see more detailed response in other subject line about slave units.  G

Thanks GGG! I am happy to hear there is a fix! I did read what you posted on the other subject line and that makes sense. But I still do not know where to send it  or what I would need to send? Any help here would be much appreciated! Bill

GGG email is in his signature, that is how I usually contact him and then he will send you where to mail your stuff and what he wants you to send. I have had him work on my MTH stuff and have always been 😄.

Do you have a fuse in your system to try to prevent damage in the event of a derailment? I use a 10amp automotive spade type that blows pretty fast and so far I have not had an issue with a failed board from a derailment.

@terryd73 posted:

Do you have a fuse in your system to try to prevent damage in the event of a derailment? I use a 10amp automotive spade type that blows pretty fast and so far I have not had an issue with a failed board from a derailment.

Thanks for that info! I will try to contact him that way. I do not have a fuse in my system as when this happens it trips the circuit breaker on my transformer. I don't know how fast that happens so adding a fuse sounds reasonable. Where did you place yours?

In the red wire from the transformer to the TIU and I generally run two locomotives off of it. I sometimes run my 2-8-8-8-2 triplex and my F3 ABA units simultaneously which is a total of 6 motors running at the same time and the 10 amp fuse never blows unless I have a derailment.