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
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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. 

Rod

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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