Electronic Fly Swatter dead.

Discussion in 'Technical Repair' started by Tonyr1084, Mar 13, 2018.

  1. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Here's a diagram of what I can trace out from the circuit. It's dead because I tried to power it with higher power. So I blew something out. Not sure what went out but - - -. And Q1 ? ? ? Not sure if it's NPN, PNP or maybe a FET. The resistors seem to check out. The diode checks out and the capacitor also checks. The transistor? Not sure about it. Probably blew out. The transformer - I have no clue what it may be. It has no markings.

    Tried an NPN transistor and tried a PNP transistor. In neither case did it do anything. The LED comes on, but it does nothing else. So I could use a little help. Keep in mind I'm not sure of what Q1 is so it may be drawn incorrectly.

    {edut} drawing removed because of inaccuracy. See post # 6 for the corrected drawing.
     
    Last edited: Mar 13, 2018
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    I would say your transformer is drawn wrong, the 670R resistor will be the Base feed and so it will be a Npn type.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
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  4. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Probably is. I have no way of telling what the transformer is or how the transformer is wired. Any suggestions as to what may be a correct drawing?

    What about the transistor? is it NPN or should it be PNP? Or FET? I have no idea.

    [edit] Oops. Thanks Dave, just noticed you already answered the NPN part. Thanks.

    [edit #2] The transformer: I'd guess that all the pins (three of them) on one side are all part of the primary and the other three are the secondary. The board is extremely easy to trace out the wiring, and unless the transformer is wound in some unexpectedly weird way (which is possible) I'd be inclined to think this is the way it's drawn. But that's why I'm here, to find out from those who know better.
     
    Last edited: Mar 13, 2018
  5. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Diode check: (out of circuit) shows open one way and shows 0.513v the other way. So I'd be inclined to think the diode is good. The transistor is new (installed it because I couldn't be sure of what the original is).

    Transistor check: (the original) shows 1.8Ω between E & B (leads both ways). Shows 3.3Ω between B & C (leads both ways) and shows 1.2Ω between E & C (leads both ways). So I'd call the original transistor shorted. Unless it's some other device masquerading as a transistor. Which I doubt.

    Is the polarity correct on my drawing? I'd think the E & C are reversed. But this is the way the original was mounted.
     
  6. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Followup: I'm not getting any oscillation at the E, B or the C on the transistor. My scope only shows a voltage drop when I push the button. To be completely honest, I have no understanding of how this thing works. And I've redrawn the circuit after having isolated the transformer so that I know this is how the transformer is wired.

    Each coil shows about 1.1Ω, so it's pretty small, and my meter is not capable of discriminating that low a resistance. And that's after having zero'd my leads.

    [edit] forgot to mention I replaced the transistor with a 2N3904 and HERE is the final CORRECT drawing.

    Electronic Fly Swatter.jpg
     
    Last edited: Mar 13, 2018
  7. RichardO

    Senior Member

    May 4, 2013
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    I think you have the wrong pinout for the transistor. The transistor in the circuit was probably BCE order and the 2N3904 is EBC order.

    Try twisting the leads on your 2N3904 to the revised pinout and see what happens. Make sure that the emitter goes to the ground side of the circuit.
     
  8. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Thanks @RichardO. If you look at the drawing, when you push the button the emitter does go to ground. Before I put any more heat to the board are you sure I have something wrong?
     
  9. RichardO

    Senior Member

    May 4, 2013
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    If you have it working then no. Otherwise, yes. ;)

    Yes, I think the emitter is drawn in the right place. If that is how you have installed the 2N3904 then all you have to do is swap the base and collector leads. I have to admit that I am doing some guessing here.

    Note that sometimes the 2Sxxxx transistors may be ECB order to further add confusion...
     
  10. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    Working on it right now. Let you know the results in a few min's.
     
  11. debe

    Senior Member

    Sep 21, 2010
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    This is what was in mine. Forgot theres a 680 ohm resistor in the + feed line.. BUG ZAPPER CICUIT.JPG BUG ZAPPER.2.JPG
     
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  12. Tonyr1084

    Thread Starter Well-Known Member

    Sep 24, 2015
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    @RichardO: Well, yes, that absolutely did it. Works just like new.

    Thanks a whole bunch! Learned something here as well.
     
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