Accidental circuit

Discussion in 'General Electronics Chat' started by dangerneck, Sep 9, 2010.

  1. dangerneck

    Thread Starter New Member

    Sep 9, 2010
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    I had constructed circuit 16 of an old Tandy 150-in-1 kits, which was a light controlled electronic harp. With my very limited knowledge of electronics I tried adding a second oscillator-looking thing to see what happened. I kind-of did that, then discovered one of the caps from the original circuit was broken.

    Anyway, I was pleased with the result. It responded by changing frequency with light intensity still, but seemed limited in the frequencies it would produce (like a piano rather than a violin, if I'm wording this badly). I tried putting it into LTspice but I don't get that program, and my circuit has a transformer in it, which I can't find in LTspice anyway.

    I kind of built the circuit and took a picture, so I could show you all, to see if you had any insight into the cool circuit I stumbled onto. This may not have been exactly what I had; the components are all correct but the connections may be a little off.

    What have I created?!
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    OH MY GOSH!

    YOU'VE DONE IT!

    oh, no...nevermind.. ;)

    This doesn't make much sense.
     
  3. marshallf3

    Well-Known Member

    Jul 26, 2010
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    It's a nice looking something or the other but knowing what the transformer schematic is might help.
     
  4. dangerneck

    Thread Starter New Member

    Sep 9, 2010
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    Well the manual just says its a 'TD-0136', and the wires leading to nothing are arranged as if they were connecting to the three terminals on the one side, with the other side being connected to a speaker. I've added a messy thing showing how it looks on the schematic in the book. Don't know if that clears it up at all.
     
  5. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Probably a 500 ohm center tapped to 8 ohm output transformer.
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Looks like you have an oscillator at Q1, but you are only showing one leg of the power being applied. Ground is connected in there somewhere. Try updating the drawing with that in mind.

    Never mind, the addition of the transformer answered that
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Q2 is modulating the freq of the oscillator at Q1 by passing it -PWM style through the winding of the transformer
     
  8. Wendy

    Moderator

    Mar 24, 2008
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  9. marshallf3

    Well-Known Member

    Jul 26, 2010
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  10. Wendy

    Moderator

    Mar 24, 2008
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    Tandy and Radio Shack are the same company, RS being a subdivision. They are likely the same part.
     
  11. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Living in a city where delivery time from Mouser is virtually overnight regardless of the shipping method, and with Mouser only charging their TRUE actual shipping cost, RS is more a desperation move for me.
     
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