UPDATE - Pics of Legacy Smoke Unit Problem

A capacitor. 100uF is the capacitance. 35V is the voltage rating.  Adjacent cap to the left looks to be the same and says Nichicon which is the manufacturer.  Frequently Nichicon caps have a 2-letter identifier on them which gets you to the exact replacement.  For example, a VK series cap looks like:

Otherwise you measure the diameter and height in mm, as well as the spacing between the leads in mm.  Then use the 100uF 35V and the dimensions to find the replacement.  For example, a cap might be 5mm diameter x 11mm tall with 2.5mm lead-spacing.  Note that the solder pads have one square and one round; that tells you +/- orientation.  A cap like this might be, say, 50 cents.  You'll pay more for shipping.

Did the rubber actually blow out the bottom? Sometime the solder joint is bad and it comes out.  Otherwise cap did go bad and the expansion pushed the rubber seal out which broke the solder joint.  Wit a good solder joint normally the top of the cap burst, which is why it is scored.  G

Thanks again Stan for your help.

The capacitor does have the name "nichicon" stamped on it as you mentioned.

If I understand correctly: 

I did observe the solder pads and the negative (-) is the circle one?  Positive the square one?

On the capacitor is a grey stripe with oblong markings.  Does this indicate the negative side of the capacitor?

And lastly.......what do the capacitors do for the operation of the smoke unit?

GGG........Thanks for your input.

Yes, the rubber was "blown" out the bottom.

Interesting about the scoring on top.

As a Tech......do you see this often?

Thanks Guys

Without help from learned friends on this board........I would have many more "shelf queens" 

Dave

The tops of many electrolytic caps are scored in manufacture as a pressure relief valve in the case of expansion.  If the case is too strong, they explode like firecrackers instead of just bulging.

Since the pictures aren't visible this morning, I can't see what you posted.

Dave, so did you find identifying marks on the capacitor?  It would be nice to know what it is for the record.

Like other cap, square=+, round=-  Stripe on cap marked with string of "-" symbols is, needless to say, "-".

Hard to say exactly what function that cap performs without a schematic.  That it is rated for 35V suggests it has something to do with smoothing the track voltage.  That is, this looks like a tight-quarters design with space being a premium - designers probably chose the lowest voltage rating to do the job.  I figure you're looking for causation or correlation but, alas, I've got nothing!

Now that I can see the pictures, I can actually provide some input.  The cap is the filter for the fan power supply from track voltage.  Before replacing the cap, I'd check the diode on top of the smoke unit, it's the surface mounted square component.  A failure of the diode will cook the cap.  It frequently cooks the LM7805 regulator as well, that's the small 3-pin part.

Yes I did Stan........ VR (M) which I matched up with ones sold on Digi Key.

They are on route and should be here this week.

You were right......shipping was four times the cost.

Could have gone to China.......but that takes way too long......and if you actually get the item!  Another story.

Thanks for the info......I will be interested to see if it makes a difference in the performance of the smoke unit.

As well.......I would like to know how this impacts the operation of the smoke unit.

Hopefully someone has this answer. 

Thanks Again

Dave

I suspect you really need at least one more component, the capacitor doesn't pop like that without a reason.  I've had many failures of the little fan regulator, but when the cap goes, it's likely to be the diode, I've seen that a couple of times.

John

I've looked at the item you speak of.......how would I know if it is cooked?

There are two caps, one beside the other......are both required to control voltage for the smoke unit fan?

Do the caps keep the fan at continuous speed......ie L M H ?

I'll post of pic of the top of the smoke unit with the diode in question.

I have smoke when the engine is running......however, on HIGH (using Legacy) I get smoke in the HIGH LOW to LOW MEDIUM range.

Nothing more.

I've re-packed the smoke unit several ways, the most recent using LIONEL rope wicking.  Same results.

Thanks

Dave

The smoke volume is controlled by the AC Regulator, the fan is supposed to get a steady 5V from the fan power supply, that cap is part of the supply.

Is it logical to conclude then that if the fan is running at a reasonable speed (not screaming fast), that the 5V regulator IC and diode are OK?  If that's the only capacitor on the input to the 78L05, then I'd think the fan would be driven with 5V pulsed at 60 Hz but spin nevertheless.

Pics John showing the diode and area.

I'm surprised they needed that much capacitance for the fan, but as Stan says, if it's running at normal speed, the regulator and diode are probably OK.

I think I'd check with a meter and see if the two caps are really in parallel.  I'm not sure what else they'd be doing there, no other components to require them.

The smoke that the unit is producing is being "fired" out of the engine noticeably so maybe the fan is running faster than it should.

I've made a mental note of this and after installing the caps (I ordered 4 so I'll change both) I'll see if any difference is made.

I'll report back on all of this later this week.

Again......Thanks Guys

Dave

If you have a volt meter measure the output at the fan connector.  If much greater than 5V the reg is bad and you will run the fan motor at higher speed and probably burn it up sooner.   G

GGG

Measured the voltage from the top of the "smoke board".

Measuring 4.39 to 4.65.

You can hear it fluctuate....and this is without one of the caps.

Only one cap is in place.

As John was mentioning.......why 2 caps if the purpose for these is only for the fan?

Thanks

Dave

Sounds like all is good just need the new cap.  I don't remember specifically with out looking at a smoke unit, but one was on the input and one on output I thought.  G

I don't have one of those exact models to look at right now, but most of them have a large cap on the input to the regulator.  I don't know why they thought they needed two.  I wonder if the input voltage is lower, perhaps they feed it with heater voltage and need the larger capacitance to get to 5V at the low heat setting?

It would be nice if we had schematics.  I could take my identical locomotive apart and check, but I don't think I want to do that.

Well Gents........my computer was down but up and running now.

I installed one cap and the only difference I could tell was that the fan motor ran without fluctuation in speed.  As noted earlier there was speed fluctuation without the second cap.

I repacked the smoke unit and it seems to run well now.

I've been using the new Lionel rope wicking.  It really can hold many times it's volume in smoke fluid..........you really have to soak it!

Digi Key was really great to deal with with respect to the parts......I had them the following day!  Not bad coming to another country.

Dave

Thanks for the update.  Your sharp pics really helped to move things along.

I suspect you might have seen a more dramatic difference with/without the 2nd capacitor if you were running conventional at lower track voltage.

In limited space designs, you'll sometimes see 2 capacitors used in place of 1 larger capacitor.  While two 100 uF capacitors takes more total volume that a hypothetical 200 uF capacitor, the available packaging options may preclude the latter.  For example, in your smoke unit the diameter of the capacitor(s) may have been a constraint.

Interesting point Stan.......I did not think of that as a possibility.

I appreciate your shared knowledge.

You've helped me over a few stumbling blocks!

Thank You

Dave

Smoke looks great, I think we can call this a wrap!

FWIW, I use two small capacitors on my Super-Chuffer for the same reason, the larger one didn't fit the footprint properly.