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Steam whistle stuck on

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Steam whistle stuck on
Posted by kgstones on Monday, January 9, 2012 11:03 AM

I have a Lionel 4-6-2 steam locomotive tender that has operated just fine until I recently put it on the track.  The whistle is now stuck on and continues to blow whenever there is current applied to the track.  I've used different power sources and have tried other engines on the same track and they all work just fine.  I'm guessing something is stuck or defective on the control board.

I would appreciate any suggestions on what might be the cause.  I can provide further details if I know what information would help.

As always, thanks for the help.

Mickey

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Posted by lionelsoni on Monday, January 9, 2012 11:58 AM

o  Model number

o  Age

o  Whether it has a whistle relay and air whistle, or electronics and a loudspeaker

Bob Nelson

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Posted by kgstones on Monday, January 9, 2012 1:39 PM

Bob,

Lionel 6-18639, Reading 4-6-2 Steam Locomotive & Tender.  Engine number 639.  There's a number on the maintenance instructions:  71-8639-250.  Instructions have a 1995 date.  I bought the engine used but I believe it's manufactured about 1995.

It has an air whistle and small circuit board with these numbers:  QA3279A.

Here's what it looks like.

I appreciate your help,

Mickey

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Posted by Kooljock1 on Monday, January 9, 2012 2:06 PM

Reverse the wires at the transformer.

 

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Posted by kgstones on Monday, January 9, 2012 2:27 PM

Thanks Jon,

I just tried that and it still keep on whistling.  I also tried a different transformer with just wire leads on the workbench and still the same thing.

Still baffled,

Mickey

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Posted by jeffrey-wimberly on Monday, January 9, 2012 3:30 PM

I used to have a G Scale loco that did that. It had a different setup though. The whistle was an air whistle on a timer. After a prescribed amount of time passed a small magnetic plunger pulled down the end of a plastic tab that was mounted on a pivot at the midpoint. The other end of the tab lifted exposing the hole for the whistle and closing a circuit that activated the motor for the whistle. It would remain activated for two or three seconds then disengage until the cycle repeated. Something went wrong with the electrical switch that activated the motor and the whistle started running all the time, making the whistle when the tab was up and making a kind of weird hum when the tab was down. I ended up disconnecting the motor.

Yours looks like it employs an electronic switch. I'm don't know much about that type but I'd wager to say the problem is on the circuit board. Your only option may be to replace the board.

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Posted by rtraincollector on Monday, January 9, 2012 3:34 PM

Call Jeff at the train tender and see what he thinks he probably tell you what to do and I bet it has something to do with replacing the electronic board. 585-229-2050

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Posted by TrainLarry on Monday, January 9, 2012 8:38 PM

The board is definitely bad.  #610-8633-010 (alternate #610-8633-020) is the part number for the board.

Brasseur has the -020 part.

Larry

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Posted by kgstones on Tuesday, January 10, 2012 9:05 AM

OK, thanks.  I'm wondering if anyone knows what part on that board is faulty and if it could be replaced.  Maybe it's just better to replace the whole board.  And, if that's what I do, I'm wondering if there is another board with better features that I could use in it's place.

Thanks all,

Mickey

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Posted by servoguy on Tuesday, January 10, 2012 4:50 PM

Your picture doesn't show the parts that likely are bad.  Somewhere on the board there must be a power transistor or electronic switch that turns on the motor.  In order to check transistors and diodes you need a meter and you need to know how to check simple semiconductors.  Diodes are very simple.  Transistors are a little more complex, but still simple.  Integrated circuits normally cannot be easily checked with a meter.  

Give us some better pictures and it is possible we could walk you through finding the bad part.

My experience with this stuff is that often the circuit designer will use a transistor that is too small, and the high current density at the junction will turn the transistor into a short circuit.  

If you can, take the circuit board off of the sticky pad that holds it and give us a picture of the back side.  This circuit looks pretty simple, so there is a chance it can be fixed.  You will need to know how to solder and have a low wattage soldering iron, maybe about 25 watts.

The QA sticker is likely the sticker of the quality assurance tester that tested the board.

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Posted by Boxcar Bill on Tuesday, January 10, 2012 5:35 PM

I would say the darlington amplifer is bad.  If I remember correctly the PN for the NPN darlington is MPSA13. I just replace the boards now. If you need a board I have them. 

 

Bill

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Posted by TrainLarry on Tuesday, January 10, 2012 6:54 PM

A top-down view of the board is here.

Larry

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Posted by gunrunnerjohn on Wednesday, January 11, 2012 7:30 AM

Maybe that little one at Q1 is sufficient for the motor?  Are there any parts on the other side?

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Posted by lionelsoni on Wednesday, January 11, 2012 9:10 AM

It would help to see the other side of the circuit card.  But it all looks so simple that I will go out on a limb and say that the diode and the larger capacitor are the DC power supply.  The 7500-ohm resistor and the smaller capacitor low-pass filter the track voltage to get the DC component that commands the whistle to blow.  The 10-kilohm resistor drives the base of what has been identified as a 500-milliampere Darlington transistor to apply the DC supply to the whistle motor.

The Darlington looks like the only possible component whose failure could make the whistle blow continuously.  Transistors typically fail shorted.  I'll bet that the assembly can be repaired simply by replacing it.

Bob Nelson

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Posted by kgstones on Wednesday, January 11, 2012 2:25 PM

I can solder this sort of thing as long as I find out what to do.  I don't know much about circuit boards and their components but would like to learn.  Here are a few more images of the back of the board and the top as well.

As I stated I don't know what each of the components is or does but would be willing to try fixing it once I knew what to do.  I really appreciate everyone's input.  A new board is only $7 and I don't know what the component I need to replace would cost or where to get it.  We have several electronics places here in town along with Radio Shack.

Thanks again,

Mickey

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Posted by kgstones on Wednesday, January 11, 2012 2:46 PM

I can solder this sort of thing as long as I find out what to do.  I don't know much about circuit boards and their components but would like to learn.  Here are a few more images of the back of the board and the top as well.

As I stated I don't know what each of the components is or does but would be willing to try fixing it once I knew what to do.  I really appreciate everyone's input.  A new board is only $7 and I don't know what the component I need to replace would cost or where to get it.  We have several electronics places here in town along with Radio Shack.

Thanks again,

Mickey

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Posted by gunrunnerjohn on Wednesday, January 11, 2012 3:24 PM

Well, the top suspect is clearly Q1, it's the only thing on the board that appears to offer the switching capability.  What are the numbers on that part?

 

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Posted by lionelsoni on Wednesday, January 11, 2012 3:35 PM

It looks like I got it right.  I notice that the card marked "98" has a 7500-ohm resistor, while the "95" card has 4700.

You can get the MPSA13 Darlington transistor (Q1) from Mouser (their part number 512-MPSA13) for 16 cents, plus $4.95 shipping by USPS.  I would order several if I were you.

Replacing Q1 should be easy.  Just cut off the bad transistor, unsolder the leads one by one, and solder in a good one with the same orientation.

Bob Nelson

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Posted by kgstones on Wednesday, January 11, 2012 3:45 PM

It has AMPS, A13 on it.

Thanks, Mickey

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Posted by kgstones on Wednesday, January 11, 2012 3:55 PM

Is this something that will probably happen again?  Our grand kids are the ones who run the trains mostly and they like the whistle.  So with more use is this going to happen again so I should get a number of these just in case?  From what you're saying I have the "95" card.  Can I upgrade it to the "98" card so that this is less likely to re-occur?  If so, how would I do that and/or is it worth it?

Following your instructions I shouldn't have a problem doing this.  Is the MPSA13 Darlington transistor a common item that I might find at a local electronics supplier?

Thanks to all of you for your help.

Mickey

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Posted by lionelsoni on Wednesday, January 11, 2012 8:46 PM

I don't recognize the part number; so I can't say whether it would be easy to find locally.  Mouser says that the part is going obsolete.  But they still have thousands in stock.

lf you want to fix it, I suggest buying a handful of those transistors and some transient-voltage suppressors (TVSs).  Put a TVS between the red and black wires to protect the gadget from the voltage spikes that probably killed it.  Put the other TVSs across your transformer terminals.

Bob Nelson

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Posted by kgstones on Thursday, January 12, 2012 10:54 AM

I've been trying to learn a bit more about these components.  My knowledge is very limited.  I tried to locate the TVSs and from what I'm seeing they're a bit expensive, much more than the card itself.  Plus I can't tell what they look like and what size they are.  If that's true then I'm probably over doing this by trying to fix the card beyond just replacing the Darlington transistor.

Secondly, it appears these transistors come with different specs.  Is the one you're recommending a 100MHz, 30V, 1.2A or 0.5A.  I downloaded the data sheet from Mouser and it looks like the 512-MPSA13 is 1.2A.

And, is there a way to check whether the transistor is good or not before installing it?

Thanks again for all your help.

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Posted by lionelsoni on Thursday, January 12, 2012 11:56 AM

A suitable TVS is the 36-volt 1.5KE36CA.  The mouser part number is 625-1.5KE36CA-E3 and it sells for 71 cents:  http://jp.mouser.com/Search/Refine.aspx?Keyword=625-1.5KE36CA-E3 .  It looks like a diode, about .2 inch in diameter and .33 inch long.

I would go with the 1.2-ampere Fairchild part, at 16 cents:  http://jp.mouser.com/Search/ProductDetail.aspx?qs=ljbEvF4DwOPubMDR4k2uVg%3D%3D .

You can test a transistor (out of the circuit) for gross failure with a simple analog ohmmeter.  Put it on the Rx1 scale.  Connect the more-positive meter lead to the collector.  (This is more often the black lead.)  Connect the more-negative meter lead to the emitter.  If the resistance is very low, that is, a few ohms as compared to megohms, the transistor is bad.  If not, grab the metal of the collector lead with one hand.  Touch the end of the base lead with a finger of the left hand.  If the needle moves up, the transistor is probably good.

However, it is very unlikely that a new transistor will be bad.  I would just install it rather than risk damaging it by trying to test it.

Bob Nelson

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Posted by kgstones on Friday, January 13, 2012 7:38 AM

Thanks Bob and everyone else for all your help.

As soon as I get my hands on some of these parts I'll get to work.  If I put in place a TVS in the whistle tender and not between the transformer terminals just yet will that at least protect the whistle card or do I have to do both at the same time?

I'm anticipating that when I pull the leads of the bad transistor out of the card the holes for the new leads will be clogged with solder.  Is there some trick to getting the new leads into the card?  I don't have a desoldering tool.  I'm also assuming the transistor could be damaged by heat so I should be careful when soldering the new one to the card.  Sorry about all this mundane stuff but I'm new at this.

Thanks again for you help,

Mickey

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Posted by gunrunnerjohn on Friday, January 13, 2012 8:18 AM

I put a TVS diode directly across the pickups of anything I have that's electronic and rolls the rails.  That's the best way to use those.

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Posted by lionelsoni on Friday, January 13, 2012 9:03 AM

As long as there's one TVS across the circuit anywhere, everything on that circuit should be protected, including other locomotives on the same track.  But using multiple TVSs has no downside, since they are essentially open circuits until a voltage spike comes along.  If you put them in your locomotives, then those locomotives are protected wherever they run, on your track or someone else's.  If you put them on your transformer or track, then any locomotives that you run there are protected, whether they are your, already protected, locomotives or someone else's that may not have been protected.

To clean out a hole, just heat the pad and then quickly rap the card on the table.

It takes a lot of heat to damage a modern silicon transistor.  Heat was a problem decades ago with the early germanium transistors, but silicon is much more robust.  But don't apply more heat than will give you a good solid joint.  You are in more danger of lifting the pads off the card than ruining the transistor.

Bob Nelson

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Posted by kgstones on Friday, January 13, 2012 10:09 AM

Thanks again as always.  Once I get this accomplished I'll post again here just in case anyone is curious as to the outcome.

Mickey

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Posted by TrainLarry on Friday, January 13, 2012 6:49 PM

  Mickey,

  To clean off old solder from circuit boards and holes, use a desoldering braid available from Radio Shack. Heat up the joint through the braid, and the braid sucks up the solder through capillary action.

  After overvoltage surges, heat is the #2 enemy of semiconductors. Even though silicon transistors may be more tolerant of heat, it is always good practice to use a heat sink when soldering in a new device. A small tweezer with a rubber band to hold it closed, or an alligator clip from a jumper wire should be placed as close to the body of the device to protect the device from overheating.

Larry

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Posted by lionelsoni on Friday, January 13, 2012 9:24 PM

Modern reflow production techniques involve placing small amounts of solder at the points where connections are to be made and then heating the entire circuit-card assembly to the melting point of the solder, semiconductor devices and all, in an oven or with hot air.  The kind of heat that can destroy a silicon device is likely to be heat generated inside the device by its own operation, not heat applied from outside.

Using a heat sink on a lead to be soldered is however harmless.

Bob Nelson

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Posted by kgstones on Saturday, January 14, 2012 6:46 AM

Thanks Larry and Bob,

With all your help I should be OK.  I've soldered other things and can do just about anything once I know what I'm supposed to do.  My problem, as stated earlier, is I'm not familiar with small electronic components.  I see the new transistors have pretty long leads so the transistor can be kept away from the base of the card.  I suppose it depends on the space available and keeping one component away from another so they don't short each other out.  I enjoy working on stuff like this and would rather fix something if possible rather than replace and through out an almost good piece of equipment.

Thanks again for your interest in my project,

Mickey

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