Oman posted:Since the regulator employs fold-back current limiting and thermal shut down, it must be a voltage issue. Are you sure you are not exceeding the input voltage rating, 30 volts?
Quite sure, I'm applying 12VAC to the input of the supply.
GGG posted:No expert in this area, but how about the fact your pulsing DC input power instead of providing filtered DC. Your trying to do it with the large CAPs at input. They show this used with a 12VDC input and only .1uf input cap. G
Good thing you said you were no expert. 
If you look at almost any properly designed three-terminal regulator circuit, you'll see that the filter caps are on the input rectified DC power, the regulator will go nuts with half-wave DC on the input. Trace out the three components on the Lionel smoke unit, they have the diode, cap, and the regulator in that order. The 100uf cap is on the input side of the regulator. The output of the regulator goes directly to the motor, and they don't fry when you turn them on.
There filtering on the input side, that's where it's needed. There's nothing wrong with the input power.
