JLC Challenger - Odd Smoke Unit Fan Behavior

I think this engine runs the smoke directly off track power but via the switch and a cherry switch.  I believe only when the cherry switch is closed the smoke fan runs.  I trace the wiring to see if I have it correct and depress the cherry switch to see if that runs the fan.

Lionel wired these early versions a few different ways so you need to check.  The issue is to get puff the cherry switch has to close.  G

I just did a Super-Chuffer install on a JLC Challenger, it had a continuously running fan.  I believe you have a simple smoke unit 5V power supply failure.  On the one I had here, the chuff switch just triggered the sounds, not the smoke.

I would probably say this is bad on your smoke unit.

Bill

Why does it run after a reset until a command is given to the engine?  G

It runs after a command is given. It can also be the R2LC. He can apply 12v ac to the smoke unit or he can swap R2LC's. Is something over heating and going open? Probably so. Doing the above tests will eliminate two of the three problem areas 

Bill

Yep, the smoke triac or the 5V on the fan supply is the only things I see as likely.  Of course, it could be the fan motor, but I'd rate that a distant third possibility.

Thanks for the replies / suggestions!  I'm going to open it up and will let you know what I find.  I do have a spare R2LC so that will be the first thing I try.

You can measure the voltage on the fan motor with the smoke turned on, if you get no voltage there and the smoke unit resistor is getting hot, it's probably the regulator Bill pointed to.

The smoke motors draw in the 40-50 milliamp range, and that's really too much for that little regulator with no heatsink.  They are a frequent failure item.

I gots an idea...Put a Super Chuffer in it while you gots it open.

Now you're talking!

And he wouldn't have to fix the regulator either.

I read the symptoms and base my responses on what is said.  That same regulator is used on MTH PS-1 and I hardly ever replace them.  I find it hard to believe Lionel produced and continues to produce these smoke units if that regulator as designed can't handle the smoke motor.  Sure a motor gone bad can burn the regulator up, but I have not seen that often.

It is weird to me that this can run at first which means the AC power is sent to the smoke unit and that allows the regulator to get power and run the fan.

Frankly, what I do when I am seeing sporadic situations like this is plug a 6V bulb into the fan plug.  The bulb will tell you exactly what is going on.

Either something weird with half AC sent to smoke unit, or some other issue is causing this.  I would swap the R2lC, and I would make sure I am resetting correctly with proper code. 

Easy way to test the smoke unit is unplug the connector and attach a lead to center rail and to the input pin.  If the unit smokes and fan runs, the regulator is good.  I trust John when he says the cherry switch is only sounds, but Lionel does have engines that use Cherry switch to puff and maybe someone modified.  Pretty easy to check via wiring.   G

If you take a stock Lionel fan driven smoke unit and connect it and run it for an extended period and measure the operating temperature of the LM78L05 regulator, you'll get a reading in the 80-100C range.  This is way too hot in open air for that regulator.  Yes, it'll probably run for a spell, but I've replaced a bunch of these in the last couple of years, so I know they're near the limit.

Well, I imagine there are 10-100K or more of them out there, but we digress.  I am still baffled why it works until a TMCC command.  G

I'd have to see it to know, it is odd I'll agree.  It could be something like a loose connection that doesn't look related.

My first thought was it was set as a diesel with strobe.  But he stated he did reset with 74.  G

That is a good guess, and it does some weird stuff when you do that!

It gets you the pulsing fan and heat.  Had a K-line that was set that way.  Couldn't get my hands around it until I put the bulb in and saw it strobe!  Of course I should have reset from the beginning.  G

When I've gotten them programmed that way, I got very little heat, not enough to actually produce smoke.

Dave, here's a wiring diagram of the smoke units from that era. This would be what's in your JLC Challenger.

You can test it with a small transformer across pins 1 and 2 up to 18 volts. On these early units, if the element opens up, the regulator circuit won't work and the fan won't run. Look for a failed/failing element (most likely the sleeve is cooked onto it) and lifted traces. These units had manual smoke boost and extended holding of the 9 key would cook these up pretty good. From my testing so long ago, I noticed that even the solder for the element would melt after too much boost and would solidify again when cool giving you an intermittent smoker. I used to put heat tape under these boards to keep the traces from burning up. There's also a chance the big triac on the R2LC could have unsoldered itself as I had one or two do that back when I used to play with smoke units.

Yep, exactly what I find in those when I upgrade them.  They run continuous and are powered from the smoke output of the R2LC in the Challenger, as well as many other similar vintage TMCC steamers.

I will probably regret this but here's my old smoke pages from 2002:

http://norm.beesky.com/old_smoke.html

http://norm.beesky.com/old_smoke2.htm

Norm, nice tip on the foil backing on the board, I'm going to give that a try.

Norm, Why would the Regulator stop working when the resistor element opens?  The only way that is possible is if the Smoke Triac is only passing half AC signal.  Which I guess is a possibility.

That is what is so amazing about the MTH design.  As far as efficiency and effectively no worries about element placement or wick placement it produces plenty of smoke.  I really wonder why Lionel has not adopted a dual element unit, especially now that they have moved to a DC and separate smoke supply with the latest boards.  G

I'm wondering if MTH has some sort of patent on dual element smoke units.

George, the smoke triac always passes half-wave except when you are boosting the smoke, then it's a full-wave AC signal.  However, it's positive and looks the same after the diode on the board.  I'm not sure why this would affect the regulator, my contention is it's simply overloaded.

Just better engineers at "that" time...oops did I say that!  I found an old technical document on heater element rating and efficiency.  Proximity of additional elements, space size, air flow are all items that go into the calculation.

It really is an elegant design.  Pinch the wick between two elements.  What better way to get the fluid and wick in direct contact.  Short one out for a 16 ohm element at low voltage and allow it to kick in series for 32 at high voltage.  Get the best of high and low voltage operations.  Beats the signal element optimized for safety vice smoke output every time.  When you moved to command, keep the basic design and let the processor control the voltage.

I have seen all sorts of different methods of packing MTH units and I really have not seen a poor one other than the single element design for the small switchers.

I am still amazed that moving the single element up 1/8" on the BB changed the smoke output from unacceptable to fantastic. 

Who ever the MTH design guy was at the Korean factory, probably did some trial and error coming up with the best smoker possible.  G

I'm equally amazed that the small change in position of the smoke resistor improved the blowdown smoke so dramatically.  I half expected it to be disappointing, thinking how could that small change affect anything!

I agree that whoever came up with the MTH dual heater smoke unit was on to a very good design.

Ok guys I opened up the Challenger tonite and here is what I found ....

Swapped out R2LC with a known good replacement and still had same results. 

Pulled smoke unit out and as Norm suggested fed the unit directly with about

17v AC and had fan running and smoke production ... for about 5 seconds. 

After 5 seconds the fan stopped running and the smoke continued to be produced

but was not being forced out by the fan.

Would appear that the 5v regulator, 691LM78L05, that Boxcar Bill suggested is failing after a few seconds causing the fan to stop. 

Below are a few pics I snapped of the stock smoke unit..

Thanks guys for the suggestions / help.  I need to do a parts order for some other things so I may order a few 5v regulators also. 

Replace the fan motor too.  If the motor is starting to go bad it will draw too much current.

As a test, unplug the fan and install a 6V bulb, even a lionel 12V will work.  Test again.  If the bulb stays lite the regulator maybe ok and the fan motor is overloading it.  G

While you're at it, cut that resistor sock away, drill out the intake hole, and replace the wick, you'll get a lot better smoke.

As far as the bulb, I'd be careful picking the bulb.  The fan motor only draws around 30-40ma in operation with 5V.  Many bulbs will draw more than that and skew the results.  If you have a meter, I'd measure the current draw of the motor, it may simply be the regulator.  I've said it before and I'll say it again, that regulator gets very hot with no heatsink with 40ma through it.