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Thread: Trying to save a train

  1. #11
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    Default Re: Trying to save a train

    That is a vertical pcb with a blob -ie chip on board ? Jim already mentioned this
    Suspect that was the switching logic, guessing only two "string sets" and the lights alternated?
    Full wave rectified to support 2 sets of 150 lights each?
    Last edited by davros; 01-10-2019 at 10:45 PM.

  2. #12
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    Default Re: Trying to save a train

    That K1851D is likely a 2SK1851 DS :
    The 2SK1851 is N-channel MOS Field Effect Transistor designed for solenoid, motor and lamp driver.

    Maybe the others are too?

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  4. #13
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    Default Re: Trying to save a train

    Some of you electronics wizards just drop my jaw! What information you have pulled from that rusted, corroded, nasty piece of electronics is just amazing! I can do so many things from working on computers for 38 years that make jaws drop, but I never got into the electronics/component side of it.

    So, dumb question to the OP... what would be the option of replacing all the lights with pixels and creating your own spinning wheels, smoke stack, and light sequence with a small controller board or linked in to the rest of your light display? You're looking at 300 lights. I know sometimes preserving the originality of a prop is nostalgic, but honestly if I found something like that at a garage sale (working or not), all I want to see is if the frame is in tact (not rusted out) and that I could add smart pixels to it and have it dance to my sequences. I think it's a cool looking train and would be happy not to have to build it myself as a wood prop or welding a frame.

  5. #14
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    Default Re: Trying to save a train

    This is a good thread. I’d really like to see some other photos of the PCB, especially after cleaning. I can’t tell if there’s a vertical component with a blob or not. The 40v capacitor and trim resistor look like a simple timer set for triggering the transistors. What are the exact sequences of blinking lights? Was it train, then smokestack, train on but smokestack blinking, all at once, etc.

  6. #15
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    Default Re: Trying to save a train

    Quote Originally Posted by dcamron View Post
    This is a good thread. I’d really like to see some other photos of the PCB, especially after cleaning. I can’t tell if there’s a vertical component with a blob or not. The 40v capacitor and trim resistor look like a simple timer set for triggering the transistors. What are the exact sequences of blinking lights? Was it train, then smokestack, train on but smokestack blinking, all at once, etc.
    Yes! We all love a good challenge!

    Copy the photo into some app and enlarge it, rotate it right-side-up. Then things are easier to see.

    Lights pattern(s): YES, please describe to us what the lights did as precisely as you can. That will help us understand what the circuitry supported, and thus help us figure out the actual circuit. Then we can figure out how to restore the functionality with another circuit.

    Someone suggested fullwave bridge for 2 x 150 light strings - why go though that bother? They are incans, not LEDs. Incans work without regard to polarity I wonder if it was cheaper/easier to use a MOSFET to switch the DC voltage to the light strings, rather than AC with triacs.

    I, too, am getting excited to see the clean(er) PCB and the back side!

    Added: The strings could be 6 x 50 ct strings. Hooked up as two separate circuits of 3 (parallel) strings each. IF SO (and I stress IF), you could just temporarily (and quickly) connect 120 AC to the 2 of the 3 wires. Either one of the strings will light up, or the other, or neither. Disconnect it quickly just in case this is not right - should not harm things. By trying different sets of two wires, you should be able ot isolate the common sire (between the two strings), and the two other strings. IF THIS WORKS, you can take pictures of the light patterns so we can understand how the (alternating) lights are put on the train for effect.

    If you want to wait until we are more sure of everything, that is also a good idea.


    Jimboha
    Last edited by jimboha; 01-11-2019 at 12:11 AM.
    Springville, Utah

  7. #16
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    Default Re: Trying to save a train

    I will do my best to get some time to clean up the pcb and get more pictures. I will try and get some older video of what the train used to do as it’s not actually working even if I plug it in.

    Also I am ok if I can just get all of the lights steady on without the need of a new circuit. I may try the quick ac tap onto the wires to see if things light up.


    Sent from my iPhone using Tapatalk

  8. #17
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    Default Re: Trying to save a train

    Look at http://www.bigclive.com/noflash.htm - this looks very similar. To replace it, just use a suitable bridge rectifier instead of the PCB.
    /mike

  9. #18
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    Default Re: Trying to save a train

    More pictures









    My new theory is that this is a simple 3 channel controller that is only controlling 2 segments of the lights.

    When plugged in, all lights that are always on turn on just fine. But lights that had “motion” are blank ( was expecting this, but I think it’s still useful information)

    Thanks for the help




    Sent from my iPhone using Tapatalk

  10. #19
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    Default Re: Trying to save a train

    That's actually in pretty good shape. The connectors are probably the issue. If you cleaned those up then it might work. The first attempt I would make is to use vinegar and baking soda on the wire crimp connections. That should eat away the corrosion in about 5 minutes. If that doesn't work then you could try soldering the wires in their connectors. Some fresh solder would ensure good contact. If that still doesn't work, removing the connectors and soldering the wires directly to the PCB are an option. I'd try these things in order and see if it works.

    I agree that the vertical blob in the middle is where the switching logic is done.

    Good job on the clean-up!

  11. #20
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    Default Re: Trying to save a train

    Quote Originally Posted by dcamron View Post
    Good job on the clean-up!
    Yeah! When I saw the new photos, my reaction was, "Is this the same board or did he find a new one?"

    Can you get a picture of the flat side(s) of the 3 transistors? Or read and tell us all the markings? We're suspecting they are K1851D MOSFET power transistors, but can't tell.

    I'm also with dcamron - with a little cleanup of the wires, you should be able to get this PCB working again. I would just cut them off, strip and tin, and solder them to the corresponding solder pads on the bottom side of the PCB. Just remember that things are reversed when you turn the PCB over!

    Once that works, you might be done. Or...

    We could track down another transistor, install it in Q1, solder wires on J2-1 and common - and see what else that little timing IC can do! Note that it looks like there either was or at least has provisions for another string connected at J2-4. Let me check the bottom traces and verify that the left-most wire/connector is indeed common.

    Jimboha
    Springville, Utah

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