I have been reading some posts from several years ago concerning the modification of the above smoke unit when installing in a TMCC equipped loco. 20 ohms was mentioned as the safe limit to create more heat for the smoke unit. What wattage and what is a good source is my question.

Last edited by JPThut
Original Post

This has been recommended for the smoke unit you’ve mentioned. You can see I’ve scraped off the coating as recommended using a dremel with wire brush. I got the resistors from digi key. 


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Rod: Do you have any tips on how you wire-brush the coating off those resistors without nicking the resistor wire?

What I do is use the Dremel SS wire brush and go across the resistor parallel to the wires inside.  That minimizes the tendency to break the wires.  Also, I use a light touch to just knock the ceramic coating off.

The resistor should be a 2W or 3W wire-wound the correct physical size to fit without shorting to the sides of the bowl.  I also take the square 5W wire-wound resistors and crack the ceramic off them in a vise, a perfect resistor for smoke lives inside.

I have used 18 ohm in the 8057-200 successfully, running command. Smokes really well. I have also tried mth's 16 ohm resistor, but it is a bit much. Ideally you want about 10-12 watts to make good smoke IMO. This translates to about 0.6 amps additional load when the smoke unit is switched on. 


The problem with going lower than 20-22 ohms is the dissipation in the smoke triac, I measured the triac temperature with 18 ohms at 18V track power, and it was around 90C, a bit higher than I want to see.  The 20 ohm resistor topped out at around 75C, pretty warm, but well within reason.

FWIW, I get more than sufficient smoke with 20 ohms with TMCC, so that's my standard upgrade value.

I use 22 and 25 ohm 3 watt ceramic coated resistors and never did anything to the outer coating. They work very well, just takes a little time to heat up but smoke very well. 

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