MTH PS3 FEF 844 30-1599-1 tender went up in smoke!!! HELP ME! :(

The coupler shouldn't be hot. It's probably where the smoke came from.  There's a PS3 board in the engine also besides the one in the tender and it may have a problem.

Can the Coupler solder joints touch the axles?  You need to have it tested by Tech.  Boiler board may be fine and the specific damage is to the tender board, but something had to burn to generate smoke, so that is what needs to be isolated.  Any wires look damaged, especially black or red?   G

The coupler should have a plastic piece installed under the coupler to keep the solder joints from touching the axle I think. At least there is on some. I recommend GGG to check it out.

That plastic piece doesn't always work, I have my second MTH Imperial Big Boy to attest to that fact!  Both died when the drawbar shorted to the truck, and that's with the plastic insulator installed.  Apparently, it gets folded up and allows the contacts to hit the trailing truck frame.

Yeah I'm thinking that is what happened.  Come to think of it, I didn't notice any plastic shield protecting the coupler contacts at all.  

No wires were melted.

I think GGG is who I was told to ship my broken TIU to also.  Sigh..... gonna need a bigger box.

GGG posted:

Can the Coupler solder joints touch the axles?  You need to have it tested by Tech.  Boiler board may be fine and the specific damage is to the tender board, but something had to burn to generate smoke, so that is what needs to be isolated.  Any wires look damaged, especially black or red?   G

It doesn't appear that there is a shield to keep the solder joints from touching the axels.  No wires look damaged.  I'll try to take some pics of this area this evening and show you guys.  

Must be different than the tenders I've seen as the coupler contacts hang down and the hard clear plastic extends at least 1/4 " over the rear axle to keep the contacts away from the axle shaft.

Good post !

Are we talking about two issues here?

One being the possible coupler contacts contacting the axle and one being the trailing truck coming into contact with the drawbar.

In the first pic there there is plenty of distance between the exposed coupler contacts and the axle on my engine.

In the next two pics is where my concern lies.  The top contacts on the drawbar are exposed and when the engine and tender are connected the contacts in the pic come a whisker away from touching the bottom of the loco frame.

Should there be a covering over the exposed contacts on the drawbar in the pic?

Thanks

Dave

To localize the burn/smoke location sniff around the board, coupler, harnesses, whatever.  Sooner the better following the incident.  I'm not kidding!

The Big Boy's I'm talking about had the problem on the drawbar, they shorted and took out both boards, boiler and tender!  I've seen it twice now, so I heat-shrink that section of the drawbar before returning them.  There should be a plastic shield there, but it obviously doesn't work that well.

So would the drawbar shorting cause the rear coupler to get HOT HOT HOT as TACKINDY describes in his first post?

Gunrunner,

Sounds like a good idea to heat-shrink the drawbar on offending engines. Not all are like that.

Thanks for posting the pictures..............Joe

Not  even a plastic shield on mine.

And this was new out of the box.

I did not take notice this being my first MTH steamer with a drawbar connection.

I will shrink wrap this part for sure before I use it again.

Something we should all check.

John Peyton.........when you post your pics could you post the drawbar area to compare.

Maybe this is where your issue might be.

Thanks

Dave

Hard to say what happened to the coupler.  If that FET cooks on the board, it would put full PV on the coupler, that would certainly make it very toasty!

Ok, I see the damage now!  The coupler smells burnt up, but if you look in the second picture you will see a little chip is burnt up!  So I guess I need this repaired or is it even worth it?  Opinions?

Hopefully, it didn't damage the other PS3 board in the engine. Is this engine still under warranty? I wonder if MTH knows of this problem with the drawbar contacts being exposed on this engine?

Sometimes traces get shorted on overload and that causes other items to draw too much current.  Not the first time I have heard of a tender short overheating a coupler.

I think your looking at a tender board at minimum.  If you want to send to me I can test.  Best to send boiler board two.  That may test good and then you can consider if you want to replace the tender board.   G

tackindy posted:

 Opinions?

 

The couplers themselves are pretty bullet proof.  Since you killed power within seconds it's probably OK since I'd guess it wouldn't have had time to warp/deform from heat.  The on-board burned chip appears to have the designator Q76 or Q78 so likely a transistor/FET...and likely the coupler driver transistor given other shared war stories.  Transistors can be replaced and they are maybe $1-2 albeit these are tiny parts and takes a degree of solder re-work skill.

The bigger issue is the board does not seem to function any more.  If everything now worked except the coupler, I'd be more encouraged that a simple component replacement would solve the problem.  In any event, MTH techs have specialized test fixtures to work on these boards that mere mortals (the rest of us) do not have.  So my opinion is to send it to GGG.

Not many fixes available for the PS/3 boards, at least through official channels.  I haven't gone to a "refresher" course at MTH, maybe this summer I'll go and see if there's more information on fixing the PS/3 boards, at least I/O stuff.

I had this happen on my 0-8-0 USRA switcher less than a year ago during a lash up in reverse due to the plastic insulator was mounted backwards on the rear coupler. Replacement of the tender board and rear coupler repaired the engine under warranty.  your rear truck is different and doesn't seam to need the insulator. Seams your coil shorted in the coupler. Mine melted the wiring to the board.  It is a cool effect when it happens but not the out come.

This is the truck and coupler the other posters are talking about.

GGG posted:

Sometimes traces get shorted on overload and that causes other items to draw too much current.  Not the first time I have heard of a tender short overheating a coupler.

I think your looking at a tender board at minimum.  If you want to send to me I can test.  Best to send boiler board two.  That may test good and then you can consider if you want to replace the tender board.   G

I sent you an email on the TIU and these boards.  Thanks for the input guys!  I appreciate the help!  

I already replaced the TIU (you can read about that in another post in this forum) but this FEF is kinda sentimental as I have pics of me and my sister in front of it when we were kids when it was doing a goodwill tour.  I already put custom number boards on the boiler so I  don't want to buy a new one, and I would rather not have this as a dummie.   

I responded.  For the other guys, if you look at this FEF tender the coupler is NO WHERE near any axle or metal.  So that is not the cause.  If the drawbar side has exposed pins near the shell, Maybe that did it.  The Big Boy issue that John mentioned is totally different and was potential dual issue, but at the engine end.  Long harness and drawbar that run under cab.  Plus trailing truck that can ride up and touch bottom of drawbar pins on engine side.  G

Bit of advise I can give is turn off track power  if removing, moving or any work you do on your layout. After going through many fuses and following this practice, I have not blown a fuse on my layout in months