MTH smoke units

DC.  PS-1 use track voltage rectified so depending on track voltage.  PS-2/3 is PWM DC, so it varies depending on conventional or DCS and track voltage.  G

The smoke unit itself doesn't care what type of power is used to heat the resistor.

John if you put 9 volts across the resister it should heat up? I know the resistance is around 16 ohms.

It'll get nice and toasty at 9V, probably more than you want.  There are two resistors of 16 ohms, so you're looking at an 8 ohm load.  9V would be 10 watts, more than the smoke unit normally sees.  You probably want more like 7-8 volts max, that will be 6-8 watts.

Thanks. Its not heating and I thought it would so I guess resisters are bad,

Is it PS-2 or PS-1 smoke, you also need to be careful with some small units.  Did you measure the ohms of the elements?  G

If you're truly putting 9V on the resistor, it certainly should be getting hot.  However, as George correctly points out, it would be very useful to know exactly which MTH smoke unit you're working with.

Perhaps you could pick the one you're working with?

This is a PS1 loco. Thanks guys. I used meter and put leads on each end one measures 16.7 ohm and the other is .5 ohms.

Did you disconnect the electronics before putting battery on it in reverse?  The .5 ohm is odd/shorted.  PS-1 has 2 16 ohm resistors in series for 32 ohms and high track voltage.  When track voltage is lower it shorts across one resistor to give 16 ohms in series.  There is a schematic floating on the forum somewhere.  G

Here's the PS/1 smoke unit schematic.

I measures both in circuit maybe I will take mark them and take them out of and get a better measurement.