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Problems with sound circuit on a toy train

Discussion in 'Troubleshooting and Repair' started by Flash215, Feb 9, 2017.

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  1. Flash215

    Flash215

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    Feb 9, 2017
    Hello, I'm having issues with the sound on a Lionel G scale Polar Express. The train is powered by 6 C cell batteries and is controlled by a wireless remote. The sounds stopped working so I opened it hoping to find a loose wire to the speaker, but wasn't that lucky. I could see no visible issues, so figured it must be a bad component. I discovered one weird thing though. I noticed that if I touched a piece of metal ( tester lead, length of wire, pocket knife etc) to one of the solder joints, it would occasionally "Jump Start" the sound and it would work for a short time. There are 2 capacitors on the board which were well within my electronic capabilities to replace, so I replaced them, however it made no difference. Does anyone know what mat cause this kind of behavior? Any advice would be greatly appreciated. Thank You!
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    We love schematics but in lieu of one sharp photos can help.

    Chris
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Sounds like a dry (bad) solder joint. Re-solder this joint using some good resin-core solder. While at it, you may want to re-solder any accessible solder joint as chances are high that other joints are affected, too.
     
    CDRIVE likes this.
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    I think I've become jaded. I read that and immediately dismissed it thinking that you probably shorted two traces which may or may not have been stressful on the circuit. I'm glad Harald caught that and correctly diagnosed it. It's really not that uncommon. The two most common faulty or intermittent solder joints fall into two categories. "Cold Solder Joint" that's typically identified by the component lead floating nearly imperceptibly within the solder joint directly around the circumference of the component lead. The other common solder joint failure is called a "Halo". It usually occurs from vibration or temperature flexing of the pc board. Halos manifest themselves as a hairline 360 deg circle (discontinuity) on the outer periphery of the solder joint. Most times either one of these maladies are difficult to see without a magnifying glass (I use a headband magnifier) while wiggling the components. Good lighting helps greatly.

    Chris
     
  5. Flash215

    Flash215

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    Feb 9, 2017
    Actually, I probably should have worded my question differently. It "jump starts" the sound if I touch ANY solder joint or piece of metal on the circuit board or speaker. I had already thought about the "cold joint" possibility and checked them all. They seem to be ok.. Thank you all for your responses!
     
  6. Flash215

    Flash215

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    Feb 9, 2017
    Here are photos of the front & back of the board. If they aren't sharp enough, I'll take better ones tomorrow in the daylight. P2090012.jpg P2090014.jpg
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Have you tried pressure points on the board with a plastic or wood rod? If only metal kick starts it regardless of where (a conductive trace) on the board you touch it then I have a theory. That circuit probably employs an oscillator used as a clock time base. It's possible the added capacitance of your probe, Knife, body or other conductive material is providing the missing capacitance it needs to oscillate. I've actually seen this happen.

    Post clearer photos. maybe we can see something there. We have a member Mr. Ed (not the smart Horse :p) that can do miracles with a good photo.

    Chris
     
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Hey, I just looked at your photo again. The board looks like it's loaded with solder resin. That stuff can play havoc on some circuitry. I would highly recommend cleaning that board off with residue free electronics solvent and a toothbrush. If you don't have any I've used mineral spirits for years and never had an issue with it. It dries fast too.

    Chris
     
    JaneSongji likes this.
  9. Flash215

    Flash215

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    Feb 9, 2017
    Thanks Chris! I'll try cleaning the board and will post sharper pics tomorrow. You guys are awesome!! Thanks again!!
     
  10. Flash215

    Flash215

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    Feb 9, 2017
    Here are a few clearer photos which I hope will reveal something. I cleaned the board and tried it again. It was working for 10-15 minutes and I was just about to put the engine back together again when it quit working again. I also took a short video of me touching my knife to the back of the speaker to demonstrate what I'm talking about. I'll try to upload it too. I really appreciate your time! IMG_1465.jpg IMG_1466.jpg IMG_1467.jpg IMG_1468.jpg IMG_1474.jpg
     
  11. Flash215

    Flash215

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    Feb 9, 2017
    Hello all, Here's a link to a short video I uploaded to youtube showing what I mean with the sound being " jump started" with a pocket knife. Thanks again for your time on this issue.
     
  12. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir Flash215 . . . . . .

    . . . . . Боже мой . . . . . . . . we like whats on after your video . . . .

    We have the remote receiver board at one end of the board and then in its center, to its side, we have voltage regulation, then the brains and interfacing at the center and then finally the black epoxy topped COB with its sound generation effects and audio output that you see the foil paths to the YELLOW leads of the speaker going into.
    RARE . . .but this one has terminal interfacing to that COB .
    Soldering does not look as good on it, as the others.

    TRY THIS . . . . .
    Get and cut a lartge enough covering tab from enough cereal box cardboard to be able to fold around the top of that COB and on past the COB area on the back of the board.
    That way, your thumb will be on the top of the COB and the index finger goes to the exact opposite side of the board.
    That then permits a pincher / compressive action and your fingers not touching any circuitry, while pressing its two strips of connection sides together.

    Set up the system to run, and then initially see if the remote triggers the unit, if not, start and hold compression on that chips connections and see if the remote then responds.

    Waiting for result

    If no go see if you can have Mamma Cass' s blow dryer at hand and a " can of air " as a coolant . . . . .or some isopropyl alcohol, if desperate.


    73s de Edd
     
    Last edited by a moderator: Feb 19, 2017
  13. Flash215

    Flash215

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    1
    Feb 9, 2017
    Mr. 73s de Edd...

    Thank you very much for your response! I assume you are referring to this piece.

    COB.jpg

    I tried pinching it with the cardboard, heating it with a hairdryer, and cleaning it with 91% alcohol. I even re-heated the solder joints, but there is no change in the behavior. It is very random when touching metal to any metal on the board or speaker will start the sound. I had it working again today for about 10 minutes, then it cut out again. The motor on the locomotive is also controlled by the remote and seems to run fine, so I know the signal is coming from the remote. If you have any other recommendations I would greatly appreciate them

    Thank You,
    Flash
     
  14. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    Not that it's causing this intermittent but I still see solder splatter in that photo ...but It looks clean now! :)

    Chris
     
  15. Flash215

    Flash215

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    1
    Feb 9, 2017
    Hello, thank you all for your help. I seem to have gotten the sound working! I zoomed my photos, picked away the solder splatter where I could find it, reheated a couple of solder joints that I didn't like and cleaned the board really well. I re-assembled the locomotive and it has been working fine for a few days now. I have no idea which of my actions got it going again. Is it possible that messing with the board and introducing current jolts could have "awoken" one of the components? Maybe I'll never know, but I don't really care as long as it keeps working. I know electronics can be finicky things.
    Thanks again!!
    Flash.
     
  16. Bluejets

    Bluejets

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    Oct 5, 2014
    Call me crazy but I'd be trying another speaker next time.
     
  17. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Glad you got it working.
     
  18. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Me too. Woo Woo!

    Chis
     
  19. Flash215

    Flash215

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    Feb 9, 2017
    That was the next thing I was going to try, and will be the first thing I'll try if it stops working again.
     
  20. Audioguru

    Audioguru

    3,389
    732
    Sep 24, 2016
    You Tube uses cookies to play something that you watched before. Pretty girls at the beach?
     
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