Hi all, I have long visited here for information, but this is my first real posting. I have a lionel 6-34776 SD40-2 NW 6121 that I'm having trouble with. I recently managed to get it apart. The hidden bell that kept it attached never showed up in any tear down video I watched! Now that I have the engine apart, I pulled the smoke unit and began tearing it apart. To my surprise, after I thought I flooded the unit, the batting is almost bone dry. So this is the first problem is it still ok to go with 20 drops when applied right to the batting? Next in looking at the PCB for the smoke unit I see that the motor is marked with a positive marker and attached is a red wire. The other wire from the motor is black. That makes sense to me however when looking at the PCB I see it is marked with a + and - where the motor wires are soldered on, but they soldered the red wire to the - location and the black wire to the + location. If my motor is running backwards and sucking air in, that explains my lousy smoke. Or is this some industry secret and its supposed to be "backwards"?


Any thoughts or experience you can lend me I will greatly appreciate. If I do need to rearrange the wires it is no problem, I'm very comfortable with my iron, I just don't want to change it if its supposed to be that way. 

2015-10-18 17.36.23


A little difficult to see but the wires are backwards from what I would have expected to see...


Photos (1)
Original Post

Many of the Lionel smoke fans are wired with the black wire as positive and the red as negative, never did understand that.


As mentioned, it's "almost" universal that the fan motor should run clockwise.  I'm sure there must be a smoke unit that isn't true of, but most run CW.


You will need more than 20 drops for a dry smoke unit, when I start out dry, I typically use about 1/2 to 2/3 of the JT's MegaSteam dropper to "prime the pump".  When I work on smoke units on the bench, I've put 2/3 of a dropper in, and then about another half, and I still haven't had any overflow into the fan chamber.  They tend to take more than you might imagine, especially when dry.


Another issue is the screws that hold the smoke resistor, they tend to work loose and develop high resistance.  Make sure they're nice-n-tight.


Finally, there is the smoke regulator, they tend to be a fairly high failure rate item.  If you measure the AC across the smoke element with it running, and then change the smoke from low to medium to high on the CAB2, you should see the voltage on the smoke resistor climb for each step.  If that doesn't work, you may have a smoke regulator issue.


Thank you all gentlemen for you replies. I am in the process of figuring out which way my motor is spinning. Even with a AA (1.5V) battery it spins just too fast for my eyes to see. Admittedly my 26 year old eyes have been crap since about day one, but wow the motor just stops immediately. I'm going to just ever so lightly put a touch of white out on the top of one of the impeller blades to use as a timing mark and it should be easier to see the direction of rotation. White out comes off easily too, I have used this trick many times before. If the rotation is correct, then I'm going to assume that my problem is the dry batting. I only have the dropper that came with my engine so any ideas on how much of that I should use? 


Unfortunately, I don't have a Command remote at my disposal. This is our first legacy engine the rest are conventional, so we haven't upgraded our control system yet. We are doing a layout overhaul and with track and building expenses command is a ways down the road, since only one engine can really take advantage of it. So I won't be able to make adjustments and check the smoke level setting. If it was set very low from lionel then I'll just have to wait I suppose.


John, on your advice I checked the screws for the resistor and they are tight. I made a note in my manual about it should I ever encounter problems again! 

Well guys, the SD40-2 literally smokes like a poor serviced freight train!!! I added fluid straight into the batting while it was apart. Around 20 healthy drops. As soon as the track power came up I got a constant and healthy smoke! The problem now is the motor is so noisy. I lubed it to no avail in quieting it down, so I ordered a replacement motor to see if it quiets things down. Thank you all for your help! Also John, I looked up that smoke dropper you mentioned, I've got one coming as it looks to be the ticket to properly filing the engine without disassembly! Case closed on this one! 

That 20 drops won't last long and your batting will be bone dry. Common mistake -- People think they flooded the smoke unit, when actually 20 drops don't even saturate the batting.

Watch the smoke unit/smoke fluid videos I have in my YouTube Channel. Link is below in my signature.

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