Need help finding replacement motors for TMCC smoke units - smoke unit root cause check

The MTH smoke unit motor is BE-0000041, it's compatible with a majority of Lionel stuff.  An exception is a few smoke units have the shorter Lionel motor, those may have clearance issues with the MTH smoke motor.

First off, there is no triac on the smoke unit in your picture.  There are three components, a 1N400x (probably 3) diode, an electrolytic cap, and a TO-92 5V regulator, LM78L05 or equivalent.  If the power is applied to the smoke unit and the fan connector doesn't produce 5VDC (or close), then those components are suspect.  The three components you mention are to develop 5VDC for the fan motor from the applied voltage that is powering the smoke resistor.

Thanks John.  I realized the triac is not on this board after I wrote it. 

I will check for 5 VDC at the smoke motor connector. If it is higher than the 5 VDC or 0 VDC what should I target?

Right now the Allegheny fan motor will not work at all, will not turn with a 5 VDC applied. Not sure if the motor died on its own or if it getting too much voltage before it burned up.

Its doubtful the components died but you can verify if 5v is going to the motor with a voltmeter across the two terminal connector on the smoke board.

Pete

If the element burns out on these older smoke units you'll never 'pull up' 5V. I'd check the element first. 

Thanks Norm-

Element is good. Smoke is just sitting in the reservoir. Motor will not come on. I swapped the smoke unit out from my parts box. Its a diesel one from the same era. Everything came one. 

I was try to determine if I buy a motor and replace it will it last or burn up too. 

I suspect the motor simply went bad.  However, if you measure the voltage at the pins, it should be close to 5VDC, within around .2 volts for sure.  If it's high, it's most likely the regulator.  If it's missing, it can be any one of the components, but the regulator then the cap are the most frequent failures.  The diode is pretty robust, though I have replaced one or two.

Thanks John - That is very helpful.  I have about 4 engines with non working smoke motors all from the early 2000s.  Seems always to be the motors, but its good to know how to root cause the other components.

The problem with the regulators is the TO-92 form factor simply doesn't have the power handling capability needed for the job.  If you measure the temperature of the regulator after a period of running, it will frequently be 80-90C, that's simply too hot for continuous running.  Although the regulator is rated for 100ma, and the motors draw 30-40ma, the 100ma rating is only with some heatsinking.  I've found that the regulator is best suited for 20ma or less in free air in a confined space.

When the regulator goes,  does the motor see the full 12v and then burn up?

Actually, a vast majority of the time, the regulator just stops outputting any voltage.  It's pretty rare for a 3-terminal regulator to fail shorted, I don't recall any in my recent memory that failed that way.  If it did happen to do that, then it would certainly take out the motor.  Other components like a TVS diode frequently do fail shorted, that's a horse of another color.