SMOKE UNIT GURU NEEDED - UPDATE

The amount of current that the supply can source does not matter. The unit will basically draw the current the dictated by circuit design. The voltage applied is the important factor. If there are regulators on the board. You are likely to exceed the maximum input voltage the device can handle.

Some of the others here may know the typical voltage applied to these boards.

The voltage has remained the same at 12v DC.

I increased the transformer power because I was running a small CPU fan along with the smoke unit on the same circuit. It would work fine, then the smoke unit wouldn't work... And now nothing from the smoke unit.

A mystery to me.

I can't make out a part number on the one part (to92, transistor looking part) but I'm going to guess it is a voltage regulator.  Looking at the board, first, the heating element/resistor should always come on when the board is powered, so there should be at least some smoke, I'd think, unless something is shorted or the resistor is bad.  

Hooking it up backwards would be a problem, as the circuit uses electrolytic capacitors, and they are sensitive to polarity.  From the photo, Ground is on the middle pin of the connector.  Hooking it up backwards could have damaged the capacitors, and they could be shorting.  If the TO92 part is a regulator, however, I don't think the fan would have come on at all if power was backwards.  

I may be missing something, but the board appears to have one flaw that could cause the fan to stop working as well, but the heating element would still work.  There is no diode to protect the voltage regulator from back spikes from the motor when power is turned off.  What happens is that when you turn off power, the motor is still spinning and it acts like a generator, pumping power back into the regulator, and this can damage the part.  

I suppose, let us know if the thing heats up at all, and just the fan doesn't work, or if it does nothing at all.  The board looks very simple, and you should be able to fix it with pennies worth of parts.  

 If it heats, but the fan doesn't work, change the polarity. There is a diode that will block the fans power if only dc of the wrong polarity is fed to the unit.

 If you read the "what did you do on your layout thread" last week or the one before, I moved to a dc supply, and thought my fan regulator burned out. I just needed to reverse polarity for the dc track. 

I mean just change it at the transformer, not the leads on the motor or board, unless that is needed for every unit to match.

That's the classic Lionel smoke unit design.  Reverse polarity won't hurt it, but the fan will not run.  There is a diode, cap, and the LM7805L regulator to power the fan.  Reverse DC polarity simply gets blocked by the diode and the fan doesn't run.

That smoke unit should run fine on 12VAC with the leads swapped either way.  The transformer connects to the center lead and either outside lead of the three-pin connector, the outside pins are common on the circuit board.

I stand corrected on the reverse polarity, I missed the diode being before either capacitor.  I will stand by the lack of a diode across the motor to stop spikes from damaging the regulator to be a flaw in the design.  

Also, John, this line read confusing:  "... the outside pins are common on the circuit board."  

My brain reads it as "the outside pins are ground" which is not the case, though I believe you meant that they are commonly connected.  So, for clarity, the center pin is ground, the outside pins are Vcc Plus on a DC supply as is being used.  

Correction noted, and it's probably best to clearly state the polarity if using a DC supply.

In answer to the original question, I can't see how you have cooked these units with 12 volts DC on them, I suspect it's just the polarity issue.

I just noticed this change.

In light of the fact that it seems I tend to comment on a lot of threads where a another George, and another John tend to post, I think, from here on out it would be easiest to refer to me as "John Galt" or JGL.  I'm just looking to avoid confusion as to who is being addressed. (5-11-15)

You should just change your name to Sue.

<G,D,R>

Who has a better lawyer?

I'll "Sue" the other one

Just don't call me late for dinner.  

- Sue.

Thanks for the responses and info!

I tested the unit in question. Figured out the polarity issue.

Transformer #1: 16v DC 2Amps

Smoke unit heats and runs.

Transformer #2: 12v DC 5Amps

Smoke unit does not heat or run.

Ends up tranny #1, which  I thought was 12v, actually reads 16.1v on the meter.

Tranny #2 reads 12.3v on the meter.

So, am I to conclude that the smoke unit requires 16v or more to run?

What would be the max voltage for that unit?

Maybe I just need to be running at higher voltage.

This all stems from a problem with hooking the smoke unit into a timer circuit. The unit would not run intermittently. Random times it wouldn't turn on. ??? I was running the smoke unit wired directly to the "load" hookups on the timer. Then added a small 12v CPU fan with a voltage reduction unit inline onto the same hookup... When activated, the little CPU fan would run always, but the smoke unit would sometimes not. Bypassing the timer would usually activate the smoke unit. ???

So I thought adding a 5amp transformer would add power, but maybe I need to run the smoke unit through a relay and separate power source. ???

The random not running of the smoke unit is confusing to me. Any suggestions?

And FYI: The second smoke unit would heat up on 16v, but no fan. So then maybe a dead voltage regulator.

Bert

Are you SURE the polarity is the same?  That smoke unit should run fine on 12VDC as long as the polarity is correct.

The one that heats up with no fan sounds like the polarity is reversed as well.  The smoke resistor is directly across the power and will heat with either polarity.  The fan regulator needs the proper polarity to operate the fan.  Obviously, either smoke unit runs on AC no matter what the "polarity" is.

Thanks John.

Will do a thorough recheck with polarity.

I assumed the units had to run on DC for the electronics and fan to operate. ??? So I can just run the unit on 12v AC?

Then I'd run the smoke unit off a relay and AC transformer, leaving the CPU fan on the DC "load" from the timer.

Geez. Maybe I do need to step back and read some basic electronics books again...

They're designed to run on AC, and that will be the most trouble-free power as polarity won't be an issue.

Any of those generic Lionel smoke units with the on-board fan power should run anywhere from 6-7 VAC up to 18 VAC.  Obviously, you'll get LOTS more smoke at 18 VAC, maybe too much for some applications.  You'll also use smoke fluid a lot faster...

Yep! Unit runs and cranks out smoke at 13.5v AC. So there.

Other unit does nothing, so I will closely inspect the hookup wiring.

Next to redo the timer circuit with a relay and AC...

Thanks for the help!

Hold on!

Now I'm right back to where I started with the smoke unit not working.

Was trying to test a relay and now the smoke unit motor does not run. The unit heats up, but no motor running. So a voltage relay failure.

This is the intermittent problem that is driving me nuts. I'd really love to figure out what is going on with this smoke unit.

The second unit is hooked up and gets power to the board but no action. No heat or motor. ???

I'd love to have somebody get these working right or find out where to replace them. I've spent a LOT of time trying to figure this out...

Bert

I have no idea what you're seeing, but let's get to simple terms.

If you connect the smoke unit(S) to 12VAC and they run reliably, then when you add your relay or other controls and they don't, I suggest you stop looking at the smoke unit as the problem.

If the smoke unit doesn't work connected direct to the AC supply, then it has a problem.

I just retested both smoke units hooked straight up to 14v AC.

One smoke unit heats but no motor running.

One unit does nothing.

I'm thinking failure on the board somewhere.

The one that the heater works but the motor doesn't is most likely the LM7805 3-pin regulator.  That is running near it's limits and I replace them pretty regularly.

I can't imagine how the one doesn't have either function, the heater is directly across the power input, and the fan is really separate.  From the sound, it has two failures because the functions are separate.  The smoke resistor may be open on the one.

How about a close-up picture of the top of each PCB on the two smoke units?

Smoke unit #1.

Smoke unit #2.

Just did another test of unit #1 and the motor ran for a microsecond right when I turned the power on. Heated up. So I presume a new regulator is needed.

Actually, if the motor runs briefly and then stops, I'd suspect the motor may be drawing excessive current.  The regulator will go into shutdown if you try to draw too much current or it gets too hot. 

The only thing that comes to mind for the one with no heater is either those solder connections to the resistor are bad, or the resistor is bad.

On both of them, connect power with the fan unplugged and measure the voltage on the fan connector terminals.  They should measure 5V.  I'm assuming there are not new smoke units, they may have been abused in a former life.  You may be looking for new fan motors or perhaps the regulators.  The one likely needs a smoke resistor.

If the DC supply is variable, you can lower the voltage to 5v, and test the motors separate from the smoke and fan circuits. Separating things for testing first, is always the way to go in my book. 

 Also be aware, small transformers often produce more voltage than stated when not under load.

  A 12v 2amp power supply might put out 16v no load, 14v @ 1a draw, 12v @ 2a max., its rating.

  A low amp device if also subject to failure if fed too much voltage, is at a higher risk of failure. Not a huge concern today in that design norms usually let us get sloppy. But the trend to cost cutting numbers over quality, that may frequency might change.  

In the polarity fun I had on my unit, I assumed the regulator was bad at first, so changed it out. But I didn't have the little regulator case. I only had a Radio Shack 7805 around. So I ground down the leg tips(dremel) to match the thinner holes, noted the leg positions by data sheet and mounted it.

Slop. No math, thought, or real comparisons, though I had the data sheets. I wanted smoke now! A two dollar gamble against 10 in new parts, and very likely the larger case with the heat sink will just stand up to more abuse. Time will tell but taking out the diode or resistor isn't likely without a very bad, burnt motor issue. But I'm curious if any of you have used a 7805 while scrounging for "good enough today"

  Part of my point here is swaps can be done, but also "now" vs an order & waiting. RS or whoever locally, may not carry those mini components. But regular cases can normally be adapted if you have the room for them. EG, I had so much room I didn't shorten the 7805 legs, though I could have to retain stock dimensions.

  I also saw an RS motor very close to a smoke unit motor, possibly a match? It was in a mass produced "grab bag" of assorted parts.

 Once you do have it working, you should also check the fan motor direction. It will blow both directions by reversing motor leads. One way will move more air than the other. I've read here recently, fan leads aren't always correct. 

The motors may run, but they are likely drawing too much current.  Unless you can measure the current draw, running them at 5VDC won't tell you much.  I've seen them run, and draw 10 times their rated current!  This is not an uncommon failure mode.

More test results.

Hooking up each smoke unit to 13.5v AC results in power to the heating coil in both units (measured at the PCB solder joints).

Neither unit shows any voltage at the fan connector.

Interestingly, the voltage regulator on unit #2 gets very very hot, hotter than the smoke box. A sign of failure?

Could I swap in new voltage regulators and maybe be back in action?

Also, I did pirate the smoke unit out of a Lionel H16-44 which has the same basic dimensions. Size is an issue for me so this unit could work, but it puts out less than half the smoke the other units do. ???

How can those units I have be putting out so much smoke?

This just means power is available to the heating coil.  If the heating coil is broken, then no joy.  Measure the "ohms" (resistance) of the heating coil with no power applied.  If you don't get a reading in the neighborhood of 10 ohms (GRJ or one of the gurus will know the value for this smoke unit), then your heating coil is DOA.

It should read 5V DC so that's a problem.

Probably means your motor is stuck/jammed or shorted and the regulator is working too hard trying to drive the motor.  Some guys have repaired motors by opening it up but it requires some finesse and you can buy new motors from hobby sources for a few bucks.  AFAIK the major smoke unit makers (Lionel/MTH) use an interchangeable motor.

Maybe.  I'd insure the motors are OK - nothing impeding a smooth spinning.  Everyone has there own favorite way of testing these but if you unplug the motor from the circuit and simply apply 1.5V from a battery it should spin.  The regulator should say something like 78L05 with some additional letters following.  These cost about 50 cents from mail-order sources in the US.  You can also get them on eBay for half that or better but it takes a few weeks to get them from Asia.

Again, just measure the Ohms (resistance) of your smoke units.  For the same voltage, the resistance of the heat coil determine how much power (heat) is available to generate smoke.  Unfortunately, it's a bit confusing since the LOWER the Ohms, the higher the heat.  So if one unit has 1/2 the Ohms of another unit , it will generate twice the power (heat).

But the power (heat) is only part of the story.  The heat has to "make it" to the fluid to generate the smoke.  If there is poor heat transfer to the fluid, then all you get is heat and no smoke!  If you are up to it, open up the unit (remove those screws) and study what's going on under the hood.  I'm not familiar with your exact unit, but generally there's a wick that transfers smoke fluid to the heater coil.  This wick can be burnt black like charcoal and can't efficiently draw the fluid over the coil.  Or it can be wrapped incorrectly, or have come loose, or fill-in-the-blank.  You can buy wicks for maybe $1 a piece from any train hobby shop.

I'd think ANY train hobby shop could get your units back in order if you don't want to get your hands dirty.

Check the regulators with no load. 5v? You are likely ok. No volts? Replace it. They are only like $2.50 when expensive.

Does your meter have an amp reading? It should be able to see exactly what the motor is drawing on its own.( from your dc supply if it is a variable supply, 5v)

Reply by  Stan-"I'd think ANY train hobby shop could get your units back in order if you don't want to get your hands dirty."

What fun is that Stan?

Pop that hood.

Its just two chambers under there,(gasket?) with a low wall to hold back fluid from the fan area.  

 One chamber has the wick & resistor in it, the other is for the fan.

 Two Q-tips have less fluff and more parts than the chambers.

 While its off, consider reaming out the intake hole above the fan a drill size, to get it about the same size as the blade inside edges. It often helps increase air flow which means more smoky air coming out once this is done.

I missed Johns 7805 reference.

I'm used to seeing that # in the "normal" case size. Does it come in the small cases as that # too? Is the large case normal? Or were you generalizing with the number series.

I did have to reverse mount from the original to the 7805. And I don't remember the original number on the little one, but it wasn't a common one in my case. I know odd part numbers are everywhere, but that is often a sign of a Mfg. for wholesale version. I.e. an original part., so I wondered how close a match it was. Very close, I take it.   

The smoke resistors in most of those units should be 27 ohms, that's the "standard" Lionel value for dumb smoke units.

The 5V regulators are by far the most failure prone of the three components for the fan, but I've replaced a couple of diodes and caps as well in older units.  All of the components are very commonly used and inexpensive.

I use 3W wirewound resistor from Digikey for smoke units, you can get them in any value you need.

UPDATE - SUCCESS

Stan2004 was right on referring to the hot regulator. I opened up unit #2 and found the fan to be jamming. Perhaps the unit got banged around and the motor was pushed off center. I tweaked it a bit and and now the unit works great.

And unit #2 has no burn staining on the wicking, so I think it is a new unit.

I'm very happy to be back on track for completing my smokestack installation. Will post pics and video when it's complete.

Next, I'll check the fan on unit #1. If that's not the fix then I'll get some 78L05 regulators and see if I can't swap one in. Do I need a specific "negative" or "positive" regulator? Most I see on eBay seem to be positive. And would it make sense to get a NEC part instead of unknown China maker? Name brand a better quality part?

Thanks so much for all the info and advice! I've learned a lot about these smoke units.

The LM78L05 is a positive regulator, the LM79L05 is the negative one.  You need the LM78L05.  The LM340L is another pin compatible positive regulator.

You can get regulators pretty cheap from Digikey, the shipping is also very reasonable on small orders.

Here's a DigiKey link that should narrow it down to suitable parts starting at less than 50 cents each.  Shipping will be about $3 if you choose the USPS First Class option.

http://www.digikey.com/product...d=0&pageSize=500

Waiting weeks for parts from Asia to make a repair can be frustrating so if you want to save another buck or so, here's ebay 5 pcs for 99 cents, plus a couple bucks shipping, name brand (Fairchild Semiconductor), and US seller so I'd think you'd have them in a few days. 

http://www.ebay.com/itm/5pcs-L...;hash=item3cde789859

Being a member of short attention span theater, Id be on my way to RS by now

Thanks Stan.

Just bought the ones off eBay.

Only if you could find one that's still open.

Lucky me! A "good" one is still at end of my street.

I see he ordered already too.

UPDATE

Swapped a new voltage regulator into unit #1 and it works fine.

Thanks again to all who commented. I learned a lot about these smoke units.

Bert