Smoke fan motor runs continously

Hi folks - request a little advice.  I have a 6-18057 6-8-6 S-2 Turbine semi-scale engine on my workbench. It has a LCRU-2 with pulmor motor.  Manufacture date approximately late 1998. The smoke resistor was replaced because of infinite resistance and no continuity.  Now the smoke fan motor runs continuously.  As soon as power is applied to the track, the headlight lights, as it should, the fan motor starts, it should not, and no sounds. Once the engine is called, the sounds come on and the engine performs fine with the exception of the smoke.  The smoke fan stays on continuously, but smoke only occurs when depressing the 9 button.  As soon as the 9 button is released, smoke stops.  Again everything else works fine.  When the engine is shut down via the control system, the engine shuts down, but the smoke motor stays on.

Actions taken:

1 - factory reset was completed including the AUX1 "4".

2 - 27 ohms across the resistor.  All wires are secure.  Grounds were all checked. Continuity on all five wires serving the smoke unit (two from smoke board to fan; three from smoke board to power, ground, and serial.)

3 - placed a piece of electric tape between fan motor and shell - there is a very close clearance.

4 - fan turns freely, no obstructions.

5 - no continuity between smoke resistor and reservoir.

I am hoping someone can suggest something short of replacing the LCRU-2 board.

Thank you, Hank



Original Post

This is normal for this engine. I have it, Century Club 671, and it always runs the fan.  As far as the smoke, mine smokes great one I replaced the wicking and increased the intake hole per Mike Reagan's TMCC smoke unit improvement video.

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In order to get lots of smoke from TMCC equipped locomotives, I do the following.

  • Replace the resistor with a 3W 20 ohm wirewound resistor.
  • Replace the wick with the Lionel braided wick scrambled as per the Mike Reagan video on smoke units.
  • Drill out the intake hole to 1/4", and don't forget to enlarge the hole in the gasket.  I have a 1/4" paper punch that conveniently does the gasket.
  • Position the resistor between 1/8" to 3/16" from the PCB and close to but not under the stack.  Make sure there's good airflow from the fan chamber through the smoke chamber.
  • Insure the fan is running clockwise, I've found a few running backwards.

Doing all that should result in plenty of smoke without going into boost mode.

You can do fine with the 27 ohm, but you'll do better with 20 ohms.  If you really like smoke, it's a worthwhile change.

This weekend since I had one laying around, I replaced the 691-PCB1-045 board with the 27 ohm resistor with a new one.  Well the smoke started and it would have set a smoke alarm off!! But it did not respond the keys to turn on and off.   Then I noticed the solder joints on the resistor were melting. So I turned the engine off.  The soldier joints solidified.  So it is time to replace the LCRU-2 board.  Thank you for all of the advice and help!!  Sincerely, Hank

Hank, you can just replace the smoke triac on that board much cheaper.

Jim, you can buy 20 ohm resistors at Digikey.  Buy this 5W 20 Ohm Resistor, place it in your vice at a 45 degree angle clamping on the corners.  Tighten enough to shatter the ceramic, you come up with a perfect sized resistor for the smoke units.

It's a little math and a little "seat of the pants" experience.  The wattage is pretty universally in the 2-3 watt range, and you're looking for 5-8 watts of power dissipation in the smoke unit.  In the simplest form, the input to the smoke triac would be a pure sine wave.

Consider 18 VAC sine wave from a transformer.  The P-P voltage is 1.414 times the RMS value of 18V.  So the RMS value of the half wave computes to 12.726 volts.  In general, I consider the smoke resistor to be receiving 12 volts and work from there.  However, that was really only the starting point.  My real limitation with TMCC is the smoke triac on the R2(4)LC board.  I tuned my resistor calculations to the triac running at 75C or less after a few minutes of running.  That ended up being 20 ohms at 18VAC input to the locomotive.  If you use 12 volts and 20 ohms, you compute .6A through the smoke triac.  I'm assuming the triac drops .7 volts in half-wave operation.

The problem is, most modern electronically controlled transformers don't output a pure sine wave, so the computations get a little more complex.  That's where the seat of the pants comes in, but I'm still using 20 ohms as my self-imposed minimum smoke resistor value with TMCC smoke units.


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On the locomotive in question, the voltage  at the resistor is about 8.5v AC and about 16v with the "boost" button.  It never smoked well (pathetic actually) to begin with.  Based on the numbers above of +/-12v, I'm wondering if have an output problem with the R2LC...

It's not the R2LC, most cheap voltmeters don't read non-sine waveforms all that accurately.  I get the same numbers with a $10 voltmeter, but my 'scope shows me that the R2LC is behaving properly.

Drill out the intake hole, enlarge the stack hole as much as possible, replace the wick with the Lionel wick, and install a 20 ohm resistor.  Make sure the resistor is from 1/8" to 3/16" spacing from the PCB, and it's close to, but not under the stack exhaust.  Insure there's airflow from the fan chamber to the stack, and it should smoke great.

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