MTH Smoke unit repair/replacement

You might try typing in the cab number & road name on MTH's website.

Smart move to put in a new one.   I am not home or I could look up your number,   Hopefully George will see your post and give you a number.

What you have is a common unit.     You will have no trouble getting one.    I would want to know what burned it down.   My guess would be the fan motor died and the rest is history,

Feet, Thanks for the tip on the road number at the MTH website. I will give it a try?

Thanks for your help Marty. It was suggested the slave board that controls the smoke unit might have an issue.

the fan motor worked when I tested it with a nine volt battery. The chimney was plugged and I am curious as to if the unit burned up from lack of fluid. 

I figured I would start by replacing the smoke unit first and see if it works properly. 

I would really appreciate any info you can give me on this, as far as what part number to order.

thanks again.

Tom

AA-0000057

A bad smoke unit motor will sometimes spin at 9 volts.  Try a battery with only 5 volts left in it.  You never stated it was the slave unit or main unit, just that it was a PS2 with a 3 volt board.   Do you feel you did not put fluid in the unit?  

IF the fan stops as Marty says, it'll cook after a spell.  If the FET shorts that controls it, it'll do something similar.

I do something slightly different from Marty for fan motors.  I test them with a bench supply, any motor that won't spin at around 2VDC is bad, I've never seen a good one that won't run at very low voltages.  If the motor spins, next issue could be excessive current draw, I've seen those little motors in Lionel engines that drew hundreds of milliamps!  If they draw more than about 40ma at 5VDC, they're defective as well.

I test the same John.  I did not know if he has an available bench supply.   We have seen many that will spin at 9 volts that will not spin on lower voltage.  The FET is always an issue.  The number is in stock that Jim posted.  It is only $30.00 retail.

I guess that is a gross assumption Marty, but a simple little DC bench supply is very handy if you're going to work on this stuff.

Sorry. I should have mentioned it is a slave board (a trailing A unit) with a FET.

I ordered an entire new smoke unit. I purchased the locomotive "used" and it had this condition when I bought it. The chimney, the triangular funnel that connects the brass cup of the smoke unit to the twin exhaust stacks, is plugged solid. 

It almost seems the fluid never got to the smoke unit and it burned up that way. That or the the funnel was plugged by the plastic melting and filling in the hole from the FET board or fan failing. The funnel seems intact, otherwise. Almost like it wasn't cast properly from the factory...

thank you guys for the info and thanks for being patient with a newbie...

Tom

I installed the new smoke unit yesterday. I had to solder the old harness to the new unit, which was slightly different than the old one, but it looked like it wired up the same way.

I powered up the unit and the fan runs in the unit but the resistors in the heating side do not get warm...no smoke. Does it make a difference which wire goes to a certain end of the resistor? I didn't know if there is a possible polarity issue with the wiring. 

I am thinking the slave board may be defective. It is a PS2, 3v system.

Just for clarification, the smoke unit in question is on the slaved/powered trailing A unit...

I replaced the slave unit board with a used board and the smoke unit as well as other functions except the red marker lights, work as intended now.

 Tom