Help with experiment 11

On the book Make: Electronics I am doing experiment 11 part 1 and the light doesn't seem to flash. It stays on solidly. Can't figure out why. Can someone direct me to where I can get help?

I know that it looks like the resistor and capacitor are touching in the upper right, but they are not. I verified all the resistor values, verified the connections, but the light just stays on when it is supposed to be blinking.
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    This response is from Charles Platt, who wrote the book.

    I don't see any errors in your wiring, provided that the negative side of the electrolytic capacitor is connecting with the negative bus (not quite clear from the photo). If the capacitor is the wrong way around, that would explain it. Other possibilities:

    The transistor may have been damaged somehow. Substitute a different transistor, if you can.

    The transistor may not be the right type. Using a magnifying glass, check the part number on the transistor.

    The capacitor may be damaged. Substitute a different capacitor.

    A resistor value may be incorrect. Can't see the stripe colors clearly enough in the photograph.

    Those are the possibilities that come to mind.

    Thanks for trying my book!

    Charles
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  • I went through everything twice and nothing I tried seemed to work, I checked the resistors to make sure they were correct and they seemed to be, but no luck.

    Then I looked at the book again one last time and realized R1 read 470K, and I had read it as 470.

    Replaced the resistor to the correct value and it worked.

    Thanks for your help!
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  • Once the speaker comes into play, hook a potentiometer where R-5 was and play with the sound like a synth. I highly suggest adding this to any new revisions of the book. As a music player and lover, this made me giddy
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  • Unfortunately the unijunction transistor is pretty much obsolete now, and this circuit is being retired from the second edition of the book (which I am working on). But I'll try to do something similar to your suggest, Mr. Lizard.
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  • Hello Mr. Platt and others,

    I was wondering if someone could give me an explanation on why you get two audible sounds. I have separated the two 'oscillators' and the connected each one separately to the amplifier circuit. The slow oscillator just give you a 'tick', which makes sense. The fast oscillator give you a fairly high frequency buzz. Again, which makes sense. When you stick them together, you get two audible frequencies, but different from the original. Without the smoothing capacitor, I would think that the gate voltage for the second PUT would be constant and just changed the threshold. That doesn't seem to be the case as you can hear two different sounds. Here is how I am looking at it:

    The smoothing capacitor varies the gate voltage => varying the threshold
    Varying the threshold can increase or decrease the speed of the oscillations (just as the capacitor and the resistor could)

    Eh, after writing this, I may understand. You can change the sound 'oscillations' of the second circuit by either changing the capacitor, the resistor or the threshold of the gate by changing the oscillations of the first circuit (a higher threshold would mean a longer time for the capacitor to charge to break through => lowering the frequency and vise versa.) The second sound, the lower tone, is actually the 'trigger' circuit causing the second circuit to be at a lower frequency. The smoothing capacitor is there to give it the 'whoop' kind of sound.

    I hope I am close, because it is beginning to make
    sense to me, which is scary.

    Thanks you for any assistance.
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