# 8632 replaced smoke unit blew out lamp!!



## ftauss (Sep 18, 2012)

Got an 8632, a can motored 4-4-2. Smoke unit burned up, ordered a new from Lionel. The one I got had an LED attached to replace the bulb, bulb socket is still there. Carefully examined the old setup, snipped, soldered and shrinkwrapped. Stuffed the LED in the headlamp opening. Took it to the track. LED looked good, for about 1.5 secs.

There is no current limiting device on the LED, wires were just soldered to the lugs on both sides of the smoke unit/lamp socket. The power lead is shared with the smoke unit though the line runs back to the smoke on/off switch.

So what happened? Did I miss something? Was there supposed to be a curent limiting device somewhere?

Gotta send an email to Lionel next.


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## T-Man (May 16, 2008)

Trying to run an LED on an AC motor is tricky. The screw type LED are made to replace bulbs. Personally I don't see how they work in an engine without a capacitor protection. I would think they would be short lived. A single LED needs 1 k resitance to work with the voltage in DC. WIth AC you need a bridge. We have plenty on LEDs it had all been said. WIth the 8632 stick with a bulb unless you want to experiment. If you have the electronic e unit the I woulld say use an LED with the 1 K. Now I do not have an LED light in a motor without less than four diodes and a resistor. The HO users have a 1 uf bipolar capacitor across the DC motor. No standard has been set for using one with an AC motor.


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## ftauss (Sep 18, 2012)

That is exactly what I thought. The tail iight I put in the PE observation car had a small PCB betweeh the power leads (direct from track pickups) and the LED. 

I need to trace the wore back a little farther and see where the voltage comes from. Lionel sells a replacement LED that says it has a resistor. I dunno, I didn't think I saw one unless it was REALLY small and uhder the tape at the end of LED. Since it was a replacement unit from Lionel and I gave them all the model numbers and it was thier reccomended replacement, one would think they had thought it through.

Damn pity, I liked how the light was concentrated out the headlight and not everywhere. And it was brighter than I expected. Briefly.

I sent a note to Lionel, let's see what they say for themselves.


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## gunrunnerjohn (Nov 10, 2010)

You don't really need four diodes, just a single diode will do fine for an LED. With half-wave rectification, you get roughly half the DC voltage you'd get with the bridge, so you're talking a maximum of 9V, assuming you have a standard transformer that puts out 18VAC max.

For a white LED, that means you have to drop 6V across the resistor and the remaining 3V across the LED. For 20ma (max current for the LED), you need at least 300 ohms. In this scenario, I'd probably pick a 470 ohm resistor, you'll never notice the difference and you won't be running the LED at it's current limit.


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## Don Trinko (Oct 23, 2012)

Not recommended but the LED is a diode and will provide 1/2 wave rectification IF the reverse voltage capability of the LED is enough for the reverse voltage.
Typically LEDs are not made for this and the reverse breakdown voltage is fairly low.
I have done this on AC but with a resistor and it will work at low voltages but again; not recommended and do not count on it. Don


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## gunrunnerjohn (Nov 10, 2010)

That's why I specifically specify a diode for any AC installation of an LED, even with the resistor. The reverse breakdown voltage of most typical LED's is in the 5-7 volt range, that will easily be exceeded in most model train applications. I wired up several locomotives with no resistor, and I lost several headlights as a result of it.


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## NYC 5344 (Dec 26, 2012)

I don't recommend half rectification unless you don't mind a flicker in the LED. A full AC Sine wave goes positive negative positive... in an endless cycle. Using only 2 diodes (a diode and the LED) only eliminates the wave when it is negative so that it goes positive off positive off... This makes the LED flicker, and it is noticeable when a train is moving. Putting a full bridge rectifier in, the negative portion of the wave is turned positive, so that it is positive positive positive... Problem solved. Just also, you need to use a 1K resistor in series with the LED to limit the current. Also, there will be a barely imperceptible flicker using a full bridge, so using a small capacitor across the leads of the LED will completely eliminate this. It is actually a lot simpler than it may seem, and uses only about 2 dollars worth of components.


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## ColtsKurt (Jan 28, 2012)

You guys really ought to speak english, here... lol :laugh:


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## gunrunnerjohn (Nov 10, 2010)

You will never see a flicker with a single diode, the eye's persistence is way slower than 60hz, that's a non-issue. I've done dozens of locomotives with a single diode and resistor, and I've never seen or had a complaint about headlight flicker.


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## tjcruiser (Jan 10, 2010)

Didn't we see a trick here a while back where you can wire two LED's in parallel, but in opposing directions. That way, the AC power going through the combination will always activate / light one of the LED's.

(See, John ... you got me thinking 'bout LED's!)

TJ


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## gunrunnerjohn (Nov 10, 2010)

Yep, if you have two LED's, you can use them to protect each other. One lights, and the other is protected since the voltage across the lit one is lower than the max reverse voltage of the one that's not lit. OTOH, if you only need one, I just use a diode. You can wire the diode in series or across the LED, dealer's choice. The object of the exercise is to protect the LED from excessive reverse voltage.


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## T-Man (May 16, 2008)

Maybe it was poor solder skills but I tried one diode on an engine and the LED did not last. That is why I went to four on engines. My 600 mkt has that. I would not recommend one. For me the test failed.


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## Don Trinko (Oct 23, 2012)

You need a resistor either way .(for LEDs) to small a resistor and they will not last. Many of the older (radio Shack from years ago) LEDs in my junk box are not very bright. Don


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## Dave Sams (Nov 24, 2010)

I have about 8 diecast cars on my layout with 2 LEDs each for headlights. I've put one diode in each. Many times we run the trains without overhead lights and don't see any flickering. I may try wiring one car using the LEDs to protect each other.


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## ftauss (Sep 18, 2012)

Problem is worse than this. I hooked up the new smoke unit and I got the same thing I got before. Lots of acrid foul smelling smoke, not the scented stuff and after a short run it started shorting the trasnsformer, The train kept going but slowed down. When I turned the smoke switch off it stopped shorting.

So I traced the wire paritally, the smoke unit and lamp are on the same lead. the smoke unit taps from the wire going to the lamp and goes back to the switch. I installed the new smoke unit exactly like the one I removed.

So I get 2 fried smoke units, shorts when the smoke it is turned on and a fried LED. I would have to cvonclude that there is to much voltage on the line going to the lamp/smoke unit. The incandescent seems bright even at lower speeds. I have to trace the wire all the way back to the rectifier and then meter the output to see what's what. Kinda worries me what else is wrong on the PCB, though it otherwise seems OK. Do we know what the DC voltage should be from the rectifier to lamp/smoke unit?


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## gunrunnerjohn (Nov 10, 2010)

I'm guessing you have a short somewhere.

I don't know what is on the PCB you mention, so I can't say what voltage you should see. Here's the Lionel Parts PARR 8032 Locomotive

Looking at the parts, I don't see any PCB where the smoke unit connects. The only PCB is the reverse unit, and it has no connection for a smoke unit. The LED does appear to connect out of sight under the smoke unit, so I have no idea what it's powered by. I think I'd have to have more details or see this one to unravel the mystery.


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## ftauss (Sep 18, 2012)

Yeah I sent an email to Lionel. What I meant by PCB is I'm "assuming" that the rectifier is mounted on the E-Unit PCB. I'm "assuming" the voltage on that line is DC because of the LED. The LED is/was soldered to the lugs on both sides of the lamp socket. And they are both powered by the same wire. I need to take a better look at the wiring tonite. I bought it second hand but it doesn't look like it was run much. And it did work the first few times I ran it.

<Big sigh> It doesn't seem to matter which scale - N, HO and now O - I seem to spend more time wrenching the running.


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## gunrunnerjohn (Nov 10, 2010)

I can't imagine the smoke unit in parallel with the LED without any resistors or diodes, I know that smoke unit won't run worth a hoot on 3 volts!  The reverse board gets track voltage, and I suppose they could be tapping that off for the smoke unit, but that board is incapable of generating any other voltages for off-board use.


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## ftauss (Sep 18, 2012)

Honestly, I thought it didn't look "right" but it looked "original". Maybe I can get Lionel to give a me a schematic of how it's supposed to be wired. I suppose the chucklehead who had it before I did screwed it up, but neatly. Grumble, grumble.

The older Scout (Pullmore) uses a single line to power the incandescent and the smoke unit, um in parallel(?), wire comes from the track power attachs to the right lug of the unit (viewed from front). Then the smoke resistor is also soldered there and then to the other side of the unit where there is another lug. The lugs themselves are part of the lamp socket, wiggle the lug and the brass in the socket dances with it. The left side has a ground wire down the the pilot truck. So the newer one looks right-ish but I had the same question about the smoke resistor and the LED being on the same circuit, even though they are still in parallel. The power consumption seems so disparate that it it doesn't seem rational.

Electricity and I are still getting acquainted. I mean I can solder and have donw home wiring repairs and installs, but this more delicate stuff is still kinda new.


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## T-Man (May 16, 2008)

The bad smell was the LED.

Supp 21 has the basic wiring diagram page 12 in adobe and page a- 49 on the page.


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## ftauss (Sep 18, 2012)

Well, I already see something different. The schematic doesn't have the smoke unit cut off switch. However it dies show the board so I'll tear it down and compare it tonite. Thanks!


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## gunrunnerjohn (Nov 10, 2010)

That looks right, the smoke unit goes right to the track pickups as I suggested. Clearly, the diode can't run on track voltage, you'll need a new LED, a resistor, and a diode if you want to fix it.


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## ftauss (Sep 18, 2012)

Lionel already responded. They are sending a new smoke unit and they gave me an idea what to look for. Gonna take the schematic T-Man supplied and take a gander.

Thanks guys!


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## ftauss (Sep 18, 2012)

Oh yeah. According to the 2nd email from Lionel there may have been an ahem, error, when they were transitioning to the LED headlights and told me what to look for. Indeed, the track power wire was routed up to the wire nut and joined with the wire to the E-unit and the wires to the smoke and lamp. The tech said the smoker and lamp could not take track power AC and that is exactly what they were getting and my symptoms were what they expected. I think he said 10 VDC was what they were supposed to get.

The schematic provided yesterday helped but the E-unit I have is a 610-0103-100 and the schematic showed 600-0103-001 so I asked him for a new scematic, too, just to be sure. Unfortuneately I don't have the patience to hack through so many unindexed supplements.

Now I just need to wait for the new smoke unit and LED and schematic to rewire it.

Now I know why I got it so cheap in barely used condition. Wonder how many more are out there like this, if it's confined to the 4-4-2s and if it's just the units manufactured during the transition to LEDs? If they'd put it on a track to power it up before boxing it the problem should have been immediately obvious. Can't beleive they don't pull 1 in 10, 1 in 100 or 1 in 1,000 just for a spot check.

Thanks guys.


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## gunrunnerjohn (Nov 10, 2010)

Interesting that they screwed it up at the factory. I'm not sure why they say the smoke unit can't take track power, that's normally what they get in other locomotives. Don't have one of these to compare...


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## ftauss (Sep 18, 2012)

gunrunnerjohn said:


> Interesting that they screwed it up at the factory. I'm not sure why they say the smoke unit can't take track power, that's normally what they get in other locomotives. Don't have one of these to compare...


I won't know for sure until I see the schematic but my first thought was it's getting track power AC and rectified DC. 18 VAC + 10 VDC. Ouch. Kinda surprised the LED didn't fly out of the smoke stack. 

He also commented that a number of the LEDs came through without resistors. I found the one I took out and sure enough, no resistor.

There is actually an LED on the parts list you put up that said LED with resistor. Hmmmm.

How's that offshore manufacturing working out for ya, Lionel? My personal belief is that (many, not just trains) items are being manufactured by people with almost no cultural literacy on thier ownership and use. They manufacure to spec, box them up and the buyer gets to beta test them. I personally beleive that if they were made in a factory in the US, by people with an interest in them these little things would be caught much sooner. It seems obvious when you know what you are looking for but who speced the wiring diagram that exposed an LED to unfiltered, unrectified AC track voltage?

Now me, I'm a developer. I make lots of mistakes at work, things rarely work the first time. But I expect that and build in time for corrections and run test cycles to look for anomalies. Which is why I have happy users.


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## T-Man (May 16, 2008)

These are very common engines and it is intersting to note their problems. Some diagrams I have seen for other engines have a bipolar capacitor across the motor connections . I am guessing in the 1 uf range. Perhaps you should try that too.

The indexing is ominous but an be rewarding. I will have another look. I may have one in the paper files I can trace back.


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## gunrunnerjohn (Nov 10, 2010)

Many TMCC locomotives have a 1uf cap across the motors, and all AC TMCC locomotives have them from each brush to frame common. When I experience issues with electrical noise or flaky running, that's one of the first steps I take.


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## Don Trinko (Oct 23, 2012)

I had a similar problem; A new Lionel Ebay loco, The light didn't work then was real brite, then went out completely, smoke worked fine. My repair dealer is waiting for parts. Over a month so far. Don


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## ftauss (Sep 18, 2012)

I got my smoke unit with LED yesterday. I went and rewired the loco with the help of a meter to make sure the correct current was going to the right place. I got the motor turning on 10 VDC so I'm pretty comfortable with that so far.

The tech reccomended that I use track power routed through the on/off switch for the smoke unit and a tap into the 10 VDC line to the can motor for the LED. Now I see no resistor anywhere on the wires to the LED. It's shrink wrapped on the legs of the LED where it's soldered to the wires but they are pretty much the same diameter as the wires and LED legs.

So I called Lionel and the tech said that the 10 VDC to the LED was correct but that the LED was probably only 5 VDC. So I asked about the resistor. He went and got one and said he didn't know the value but it was striped GOLD-RED-BLUE-GREEN. My handy dandy resistor calculator says this is 5.6k Ohms 5%. Does this sound right? Seems high from discussions here, but... I have a box full of resistors so I'm ready to go, just need to know the right one.

According to something I read here just now, I only need a 5 VDC drop so at best 250 Ohms (50 * 5) so a 270 maybe?


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## Dave Sams (Nov 24, 2010)

I can't wait any longer to chime in. 5.6k sounds like an awful lot. The bands should read green blue red gold. But I wonder if the "tech" was mistaking brown for red. 560 ohms is right for 5 volts. But 5 volts sounds like a lot. I'd feel better trying a 680 ohm or 1k resistor. How high does your transformer go? Mine gets to 16v and I use a 680 ohm resistor when I replace headlights with LEDs.

Sit tight, there will probably be more to come.


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## gunrunnerjohn (Nov 10, 2010)

5.6K will barely light the LED. If it's powered directly from the track, you need something on the order of a 1K and a diode to block the AC from the LED.


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## Dave Sams (Nov 24, 2010)

The description says the line going to the motor is DC. If this is so, you don't need the diode. But, if you get the leeds to the LED wrong, the LED won't work. Don't fret, just reverse the leeds.

Been there lots of times


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## ftauss (Sep 18, 2012)

Ya know, I'm looking at this thing and I just realized that the red wire on the LED is connected to the same lug that has the ground to the outside rail.

In addition it occured to me that if I want to use the motor leads than it will be wired either in parallel or series WITH the motor. Since the motor consumes voltage that would reduce the voltage that is supplied to the LED.

Now I'm thinking I should connect both sides of the LED to the same color wires that are connected to the motor. I have a small DC power supply I'm going to use to test the LED's direction of flow. And then meter the current flow to the motor. 

Now I'm curious what the motor consumption will be and if there is a danger of voltage spikes that could damage the LED. I have a range of resistors I bought from 47 Ohm on up, standard values 100, 150, 270, 330, 470, 680, 1k.


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## gunrunnerjohn (Nov 10, 2010)

Since the motor reverses polarity for direction reversal, I'm not so sure your analysis is correct.


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## ftauss (Sep 18, 2012)

Huh? DC power is supplied to the motor, no? Isn't that what will be present on the 2 wires going to the can motor?


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## gunrunnerjohn (Nov 10, 2010)

Correct, but when you want to reverse the locomotive, the polarity of the DC on the motor is also reversed. Without protection for the LED, it sees what can be excess reverse voltage.


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## Dave Sams (Nov 24, 2010)

Direct current goes to the DC motor. To reverse the direction of the loco, the e unit switches the direction of the current flow. 

For example + to red wire - to black wire goes one direction. 

- to red wire + to black reverses the direction. 

Can you wire the LED to the frame and pickup (through the resistor and diode)?


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## gunrunnerjohn (Nov 10, 2010)

Wiring to the pickups with a resistor and diode is probably preferred, it'll keep the lights on all the time.


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## ftauss (Sep 18, 2012)

Crap, didn't think of that.

At about ~18VAC, metered from a 1033, I get ~15 VDC measured in parallel to the motor with no load ie not mounted and driving the wheels from the E-unit.

I think gunrunner's rectifier diamond might be one answer. I think for the moment I'm going to put it together with an incandescent and then give this some thought.

Of course you could make the argument that the light should shut off when backing up.

I was playing with some LEDs I'd bought at the shack a while back. Seemed to me they got as bright as they were going to pretty quick and then stayed as bright until the failed. I did have the surprise of having a red LED blowup, literally. I was playing with a DC train transformer and observing the voltages and brightnesses. I had cranked it up to the neg side and went all the way up 15+VDC. It glowed briefly and then poof. Interesting lesson.


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## gunrunnerjohn (Nov 10, 2010)

Most of the steamers I have, even the Legacy models with the fancy lighting, leave the steamer headlight on all the time. OTOH, most of the diesel models have fully directional headlights.

Now your education is complete, you can smoke LED's on command.


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## Dave Sams (Nov 24, 2010)

ftauss said:


> Crap, didn't think of that.
> 
> At about ~18VAC, metered from a 1033, I get ~15 VDC measured in parallel to the motor with no load ie not mounted and driving the wheels from the E-unit.
> 
> ...


If you are going to experiment (learn) with LEDs, RS is an expensive place to buy. I received 100 yellow 3mm LEDs for $4 shipped from E Bay. I had to buy resistors, separately, which ran another $1.50 delivered. I don't understand how they do it. Last year, I got 100 diodes for $1.00 shipped.


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