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MTH 260 PS2, no smoke or lights going forward

samdjr74samdjr74OGR Forum Member

Hi All,

 

I was running the trains this evening and saw that the headlight wasn't working on my MTH 260 loco. After looking at it a little better I noticed that it wasn't smoking out of the stack either. I put the train in neutral and the light comes on as well as smokes. I put it in reverse and the light comes and smokes as well. Back to moving forward and still no lights or smoke. The train seems to be running fine besides the problems mentioned above. Last year I had an issue where one of the capacitors above the tender pin on the loco burnt up. I replaced it and the train has been working fine since until tonight. I'm not sure where to start. I just checked the capacitor again and it seems fine. Any ideas?

 

Thanks,

Sam

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samdjr74samdjr74OGR Forum Member
Thanks, that's it, the diode. And looking back at my notes it's almost identical to the last time I had this problem. The fix should cost less than a buck but here's my follow up question, what could be causing this to happen? I've been running MTH and PS2 engines for years and this engine in particular is the only one to give me a problem like this.
 
Originally Posted by GGG:

Do you mean diode?  Sounds like one of the diodes that makes the positive voltage for the engine has failed.  It is under the PCB on the engine where the tender tether plugs in.   Either diode failed or it has a cold solder joint.  Probably the one from the yellow motor wire.  G

 

G GGGOGR Forum Member

Most likely a short or pinched wire from the diode.  Think purple PV for the lights or the smoke unit heater.  That would cause additional current to flow through the diode to chassis ground.  Would not effect electronics so much, but could cause over current through diode.

 

Also make sure diode leads not near Chassis where they could short.  G

gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

I think George has nailed it, this sure sounds like the diode has died.  It certainly fits the symptoms perfectly.

 

Perhaps something like the smoke unit is drawing more power than it should and causing the diodes to fail.  If you've had the failure before, something must be triggering it.  Since you're normally running forward I expect, that diode would have more chance to heat up and fail if overloaded.

samdjr74samdjr74OGR Forum Member
Yep, George was right, the diode again.
 
I'm wondering if I move the diode to inside the boiler I could put in a larger one that shouldn't overheat as much, thoughts?
 
 
Originally Posted by gunrunnerjohn:

I think George has nailed it, this sure sounds like the diode has died.  It certainly fits the symptoms perfectly.

 

Perhaps something like the smoke unit is drawing more power than it should and causing the diodes to fail.  If you've had the failure before, something must be triggering it.  Since you're normally running forward I expect, that diode would have more chance to heat up and fail if overloaded.

 

gunrunnerjohngunrunnerjohnOGR Forum Member SUPPORTING MEMBERDIGITAL SUBSCRIBER

I don't think a larger diode is the answer.  Something is causing those to die, I think you need to find out what it is.

 

Top suspect for me would be the smoke unit, measure the resistance of the smoke elements and see that they are close to 8 ohms, something in the 7-9 range is probably good.  That's with the smoke unit unplugged.  I'd also look for any pinched wires while you're in there.

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