PS-1 centipede trying to lower voltage to smoke units

Put a single 3A diode in series with one of the leads for the smoke units, that will cut the voltage and give you what you seek.

Thanks John....Seems to me I did that before for other applications and seem to remember voltage only dropped about just a little less than 1 volt. So I had to start putting diodes in series. So can 1 diode really drop voltage 9 volts? I am attempting to go from 18 volts down to 9 or 10 volts. you know better than I.

Different situation, the PS/1 smoke unit gets full-wave AC into a bridge rectifier.  The diode chops one half of the waveform off before it gets to the smoke unit.

Try it before you reject the idea.

John, thank you.....as I said....you know better than I,  I will give it a shot

Here is a few pics of my attempt to get this smoke unit voltage down to 9v from 18v track power. Bought these diodes off Ebay.  Hooked 1 into the circuit between pickup roller and the smoke unit. It really didnt slow it down a bit. I ended up putting 10 diodes in series to get the 9v I was looking for. This is an ugly looking bank of diodes. I guess I am doing something wrong. Any input please?

All you needed is one diode!   However, if you're running a full 18V on the track, the PS/1 smoke unit has a regulator that will boost the smoke for low voltages.  It should have reduced the smoke, but maybe not enough.

Could I install another regulator between the pickup roller and the smoke unit? If so, where would I buy 2 of those(1 for each smoke unit)?

The "direct" approach would be to simply replace the 16 ohm resistors with a higher value.  I'd probably start with 22 ohm resistors in one and see how that worked.  You could retain one diode to lower the voltage and the higher value resistors should make a substantial difference.

Part of your issue is that when you lower voltage that circuit board cuts out one resistor and you get a 16 ohm single smoke unit.  When voltage rises the second resistor is placed in series and you have a 32 ohm smoke unit.  So while you are cutting the voltage with your diode string you also are shifting to a lower resistance which also means more smoke.  You need to measure the DC voltage out of the rectifier with your set up.  If you leave smoke resistors alone you want to target a voltage high enough to keep the 2 resistors in series for 32 ohms.  So probably around 10-11 Volts DC out of the rectifier.  Or leave the smoke board alone at track voltage and change the resistors to something like 22-24 ohms for a total around 48.  Figure out what you like.  Otherwise get a variable voltage board that can drive the smoke unit at a selectable DC voltage you can set.  See what you like.  You also can use a diode to slow the smoke fan motor down.  It does spin faster at higher voltage despite the 5V regulator.  G