K-Line Smoke Unit Observation

Thanks for the info - it might come in handy some day. I agree with you on the location of  the switch - on the hot side would be better design. I had one short out a while back, but it wasn't the board - it was a poorly installed hot wire where it enters the smoke unit under the top cap. It fried the smoke triac on the R2LC board. With the assistance of some of the experts on this board - mainly Gunrunner John, and I think you might have been involved too - I was able to diagnose it and replace a $3.00 triac rather than a $30.00 board. 

Yes, I remember that.  This one is not controlled by the R2LC though.  It is conventionally powered which is interesting.

As I recall that GS-4 was one of their low priced club engines and also it was pretty shortly after K-Line licensed TMCC. My guess would be they were trying to save a little money and complexity on a low priced engine. I did the same thing when I put DCS in my Weaver brass John Wilkes - I kept the CV board and the old Seuthe smoke unit rather than deal with the hassle of mounting and wiring an MTH smoke unit. 

I think I have the same problem as did Southwest Hiawatha.  I am getting 0 volts going from the R2LC to the smoke unit element.  Possible fried triac.  Can anyone tell me where I can get a replacement triac.  My other option would be to disconnect the wire and attach it directly to rail power.  Would that work?

You can get the part from mouser or digikey.  Or you can replace the R2LC.  G

The smoke triac is 2N6071A just for info.

Sorry I don't have the Digikey PN, but its an easy search.

Rod

Sure, but they're outrageously priced at 69 cents.

http://www.digikey.com/product...2N6071AGOS-ND/918261

Actually, the beauty of Digikey is they send First Class Mail for small orders, so my typical shipping is only $2-3 for most orders.  That's the one downside of Mouser for small orders, they start at around $6 for shipping.

Thanks everyone for your responses.  I installed a new 20 ohm element and ran the hot wire from the smoke unit directly to the pickup roller.  Excellent smoking action, however, after about 60 seconds of running the element caught fire. Does the triac reduce voltage going to the smoke unit? 

Yes, running directly from the 18V track voltage, I'd suggest perhaps a 30 ohm resistor for that element.  The smoke unit receives half-wave rectified track power from the triac on the R2LC under command if it's controlled through the R2LC, so it'll dissipate much less power.

With 20 ohms at 18 volts on the smoke unit, you're dissipating over 16 watts, too much for that small unit. 

With 30 ohms at 18 volts, you'll still be dissipating 11 watts, still more than most smoke units, so you might have to go even higher.

Lionel uses 27 ohm, regardless of track voltage the R2LC passes 12V according to Lionel and 9V half rectified according to John, so the wattage is much less that stated.

In conventional the track voltage normally doesn't get that high without a derailment.  G

The difference is that for command, very few smoke units are wired directly to track power, so the fact that they have 27 ohm elements doesn't cause excess power dissipation as they're not running on the full voltage.

Try this simple experiment.  Wire one of those 27 ohm resistors to your transformer on the bench and set it to 18 volts.  Before long, you get a very hot resistor, far more than is necessary for a smoke unit.  Even if you don't reach the flash point of the smoke fluid, you'll char the wick very quickly, it's simply too much heat.

All the PW smoke units and all the conventional smoke units from Lionel up to recently were based on 27 ohm smoke elements.  Run at 12-14V normally.  There were a couple of exceptions but....

If it is conventional it is not being run at 18V and it is AC current not DC.  So wattage is less.   G

Sounds like he's running with a lot more voltage than the 20 ohm resistor will handle in his environment, it takes some effort to get them to catch fire!