I have an early modular board Legacy  -   F3 A  -  Non Powered Engine.


All systems work just fine....except for the following.

On a powered track,  with command on or not....in about 5 minutes the smoke unit will just come on by itself.  I can shut it off with the smoke buttons and 5 minutes later same thing.

Is there a problem with the Radio Board...glitch / gremlin....or maybe in the smoke regulator?  

Thanks again for the assistance.



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Last edited by Soo Line
Original Post

Top suspect is the smoke regulator, I have seen that a number of times.  I keep several common ones in stock for that reason.

Thank You John....I most appreciate your help.

I have changed these regulators before but I don't much care for the job...

The easy way is just chop the leads of the old one, leaving plenty of slack. Splice the new one onto the old wires and bolt it back down.  Be sure to get the insulating washer in there between the triac and the chassis.

The only thing to be careful of is some of the wire they use makes it hard to pick the black wire with the brown stripe, last bunch I got it was almost invisible.

I do a simple lap solder, and cover it with heat-shrink.  It's more than sufficient for this task. I tin both ends of the wires, trim to about 1/4" exposed tinned end, slip the heatshrink over one side, and then just hold them together and apply heat.  Makes a slim joint that doesn't impede getting the whole mess back in the shell.

I try to leave a little slack in the locomotive wiring so the next time I replace the regulator, I can use the same process.  Normally, I cut the regulator leads to a couple of inches.


Well I wired in a new smoke regulator....and unless it is by chance faulty,  I'm not sure how to proceed.

I resoldered one wire at a time from the old regulator to the new one.  All 5 wires were connected on the old regulator so I followed suit on the new one.  Both grounds were wired.

I reset (with AUX1 - 2) and tried a new radio board to no avail.

Happening Now :  The smoke unit is on all the time and will not respond to commands.  It does blow smoke.  It comes on immediately when power is applied and can only be shut off with the Smoke on/off switch.

This is early Legacy with modular boards.  I have not changed the smoke resistor yet from 6 to 8 OHM.

First 2 pics are the of the old regulator removed....the next 2 pics are of the new regulator wired in.   On the "old" regulator the brown wire next to the triac went to the smoke unit.  It did not have a black stripe...but the new regulator brown from there did have a black stripe.

Once again ....appreciate the help Guys.


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This one goes to the serial data, your description is somewhat confusing, but if you wired these wrong, it would be bad news.

The connections on the regulator are from right to left as shown below.

  • Smoke Heater Hot
  • Ground
  • Track Power
  • Ground
  • Serial Data

I'd verify that all of them are actually connected correctly first.

Thanks John.  Sorry for the confusion.

This one pic is of the new board wired in.

I traced the wires to make sure I had not connected incorrectly


On the right marked  S  goes to board (serial connection)

Next on the left is ground and goes to ground.

Next on the left is power.

Next on the left is ground again....going to ground on smoke unit.

Next on the left and last wire is brown and goes to Heater on smoke unit.

Could it be that the regulator is bad?   

Thanks Dave

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@Soo Line posted:

Could it be that the regulator is bad?  

Sadly, that's a real possibility.  I just got a few TMCC and Legacy ones for stock.  Given my previous experience with them, I put them on my test set and tried them out.  The Legacy ones worked OK, but the TMCC ones won't adjust the smoke volume.  They turn it on and off, so I know they're seeing the serial data.  I have older ones that some will adjust the smoke volume, and some won't.  I don't know why it's such a chore to build this simple board, but obviously it is.

Thanks John

I have another one.....like the one in white pictured.  The only one I have left.  


How can you tell the difference between TMCC ones and LEGACY ones ?

The shrink wrap pictured in Black in the photo below was the original in this engine.

The shrink wrap pictured in White in the photo below is the casing of the one I just installed.

Both regulators seem to be very similar with similar numbers and writing on them.

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It's pretty difficult to tell from the codes, but the Legacy boards should have the triac exposed and able to be bolted to the chassis (with the proper insulator), the TMCC ones do not expose the triac outside the heatshrink.  The S04 should be a Legacy model.  The SDK2507 doesn't mean anything to me.

Thanks John

Both of mine met the criteria of being bolted to the chassis with the insulator....both older stock......and both failed.

I have ordered some from Lionel....I think I notice that they are shipping out parts albeit slowly.


Yep, Lionel is shipping, it just takes some time.  Usually, after two-three weeks sitting there, it gets processed and shipped.  The funny thing is, I can't get parts from MTH, but I got the new catalogs, and they send them Priority Mail!

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