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  1. audioguru2

    in search of a FM STEREO transmitter

    Rohm stopped making their lousy analog BA1404 stereo FM transmitter IC and replaced it with with their excellent BH1417 Pll IC that is used in Silicon Chip's Micromitter.
  2. audioguru2

    Transformer and LM317 Question

    Hi Harry, Where's Sasi? His old LM301 doesn't work with its input voltages anywhere near its positive supply. The circuit was probably designed for an old LM307 which is no longer made it and a TL082 work fine with their inputs at the positive supply. Hi Indulis, The datasheet for the LM317...
  3. audioguru2

    Transformer and LM317 Question

    D3, D4 and C1 aren't necessary. The circuit regulates the voltage poorly with the 0.22 ohm resistor, and doesn't regulate the current. The circuit is just an amplified power resistor and changing the pot's setting changes the resistance. The pot setting also limits the max voltage when there is...
  4. audioguru2

    i need help extending the keys finder project. can someone help me out????

    The most exciting thing for me at the election tomorrow will be when sombody tries to vote twice or more. Some people's name is twenty words long and they were given twenty voting cards. They keep coming back dressed differently but I spot them every time!
  5. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Tomorrow I'll be busy working in Canada's national election. All day and half the night. I'm getting paid pretty well to keep politicians away from the polling station because they bribe folks to vote for them by handing out a bottle of booze! Also, I'm in charge of 10 people who check-in voters...
  6. audioguru2

    i need help extending the keys finder project. can someone help me out????

    It still looks bad on the page. Does this look better?
  7. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Does a JPG look better? The PNG looks fine when downloaded.
  8. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Hi Logan, I don't understand what your friend did. I don't know why he changed this simple bandpass filter. I redrew it to show how it works:
  9. audioguru2

    Input signal for LM3915. need help.

  10. audioguru2

    Transformer and LM317 Question

    In your original circuit, the 0.22 ohm resistor ruins the LM317's voltage regulation since the resistor causes the output voltage of the circuit to drop with increasing output current. You would set the voltage-adjusting pot for the amount of trickle-charge current you want. I have re-sketched...
  11. audioguru2

    Transformer Power Rating

    The coil is not wound around R14. It is wound on something smaller like a 1W resistor but that resistor isn't connected to the circuit.
  12. audioguru2

    Transformer Power Rating

  13. audioguru2

    Electronic Stethoscope

    The original faulty project worked? Impossible, without correcting its errors! Also deleted was the list I posted recently of its errors.
  14. audioguru2

    Electronic Stethoscope

    The 1/4 inch phone plug and jack were invented for use by telephone operators to plug-in one person calling another person. The operators used cords with phone plugs on each end to plug-in to hundreds of phone jacks in front of them. The operators did the switching. Now, 1/4 inch phone plugs...
  15. audioguru2

    Amplified Ear help!!!!

    Order the proper capacitor online. With values that are 1/10th what they should be, the sound will be shrill without any low frequencies. It would sound like just a tweeter speaker.
  16. audioguru2

    working of negative feedback

    Negative feedback is used to decrease the HIGH GAIN of an Op-AMP to a suitable value. Because the open loop gain of an Op-Amp is so high that even the noise signals can be amplifiied to an extent that can saturate the output of an Op-AMP. Negative feedback provides the benefits of reduced...
  17. audioguru2

    working of negative feedback

    Hi Shaiq, An ordinary amplifier can't have an output more than about 11Vp-p when it has a 12V supply. If it has a gain with negative feedback of 10, then any input level more than 1.1Vp-p will produce a clipped 11Vp-p output. When an amplifier clips, it produces a lot of distortion that can...
  18. audioguru2

    working of negative feedback

    Hi Shaiq, Negative feedback decreases the 200,000 gain of an opamp to a useable number. It does not perform an automatic gain control function. If the power supply voltage totals 12V and an opamp's gain is set to 10 by its negative feedback voltage divider resistors, then with a 1V input signal...
  19. audioguru2

    Some kind of RPM counter

    So why not download the datasheet for the LM2917 and use one of the tachometer circuits it shows?
  20. audioguru2

    100Hz TV???

    Hi Shahriar, Actually TV pictures are interlaced, so each complete picture is broadcast at 25 pictures per second. Interlacing causes each individual line to flicker at 25 Hz so a sophistocated TV stores each picture in a digital memory then displays it non-interlaced which is called progressive...
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