mth 484 all lights dont work help!

Chris,  Sounds like a FET shorted or the micro chip that controls the light FETs.  I have seen this before and the result is that the bulbs get high DC voltage and burn out.

Normally it occurs because of a pinched wire.  Which model is this?

It would be best to have the board tested/repaired.  Usually all the lights don't go out at once.  G

http://www.mthtrains.com/content/30-1265-1    its the northern ASTF 4-8-4.  it has the fire box glow, the interior lights also.  the markers and headlight and backup tender light.  that still works.  the smoke works.  Now the engine will slow down a little by itself and speed up.  Im wondering that board your talking about, maybe that also has something to do with the speed control, because the chuffing seemed too slow for the engine revolutions.  not sure about any of that.  thanks.  so you know where this board is located?  I see there is a small one in the engine on the boiler up inside. 

thanks

Chris

Chris,  This is an older PS-2 5V system.  The PS-2 is in the tender, the engine board is a MUX that allows one light signal to control 2 features.

I am confused you now say the headlight and markers work?  Before you stated the they did not?

The interior and firebox are on the same circuit (it is a double bulb harness).  That can blow.  SO if all the other lights work it can be the bulbs or the single FET that controls those lights.  The fact the engine is starting to act up also, worries me.  There can be a pinched wire, the harness can have an issue, it can be a bad MUX board, smoke fan can be going bad.  Is it possible the wire harness to the MUX or another wire was pinched while you were inspecting the engine?

Yes FETs can be replaced.  At this point I would recommend taking it to a MTH technician, or you can ship it to me.

The board need to be tested separate from engine to ensure all features work, then we need to figure out why the other faults.  G