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  1. audioguru2

    diode Experiment in the Kybett, Boysen "All New Electronics self teaching guide"

    It sounds like you connected your current-meter directly in parallel with the battery, instead of in series. Then you killed the battery (because a current-meter is a dead short) and maybe blew the fuse in your current-meter. But like I said before, if you turn down the pot then the current...
  2. audioguru2

    diode Experiment in the Kybett, Boysen "All New Electronics self teaching guide"

    If the battery or the diode has its polarity backwards then there will be no current. If the battery and LED have correct polarity then when the pot is turned down the current will try to be infinite which will burn the pot and kill the battery.
  3. audioguru2

    running 12v ac device on 12v dc

    Hi Ben, The peak voltage of 12VAC is 17V and a full-wave rectifier will drop it to an unregulated supply of 15.5VDC. The output voltage of the wall-wart might be higher. You might be able to connect 12VDC to the 12VAC input but it would make an unregulated supply of only 10.5DC. The output...
  4. audioguru2

    Audio amplification question

    You don't use an L-pad. Simply increase the value of the 1k input resistor to 100k.
  5. audioguru2

    Audio amplification question

    The input impedance of your inverting amplifier circuit is only 1k ohms. Many music sources cannot drive an impedance so low and need a minimum of 10k ohms for good bass response and low distortion. Then the pot should be 100k and the input resistor should be 10k.
  6. audioguru2

    Audio amplification question

    The non-inverting input on the non-inverting amplifier circuit must have its input at 0VDC or the opamp will not work properly. The input can have a 100k resistor to 0V (ground) and a 0.1uF input coupling capacitor. I have only 10 fingers so I can't count to a gain of 11. :-[
  7. audioguru2

    Audio amplification question

    Of course. The pot could be adjusted to be a dead short. I corrected the schematic:
  8. audioguru2

    Audio amplification question

    For an opamp to have gain, the negative feedback must be a portion of its output. A voltage divider makes the portion of the output.
  9. audioguru2

    Battery Charging - Help?

    Simply copy what a battery charger IC does.
  10. audioguru2

    Battery Charging - Help?

    Why not just use a battery charger IC? Or copy the circuit of a battery charger IC?
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Another member also had C7 explode in his power supply. He used the power supply to power a high power high frequency switching circuit. Your flyback circuit also has high power and high frequency which exercises C7 too much. Your flyback circuit should have its own pretty big main filter...
  12. audioguru2

    Audioguru's Electronic Stethoscope Help

    If the capacitor added between pin 1 and pin 8 of the LM386 is increased to 100uf then the very low frequency heartbeat sounds will be amplified more  than if 10uf is used. If 0.1uF is used then the gain is 200 above 1kHz and drops at lower frequencies.
  13. audioguru2

    Audioguru's Electronic Stethoscope Help

    If your circuit produces a buzz then maybe it has unshielded long wires on a breadboard that pick up mains hum. The circuit should be built compactly on a pcb or on stripboard and shielded audio cable must be used to connect to the microphone. Try the LM386 amplifier with the new 10uF capacitor...
  14. audioguru2

    Audioguru's Electronic Stethoscope Help

    The circuit should have more than enough output level. Try connecting a 10uF capacitor between pin 1 and pin 8 of the LM386 to increase its gain 10 times. The positive wire of the capacitor to pin 1.
  15. audioguru2

    Speaker Magnet

    I have seen speakers with two magnets. Bucking magnets are sold. Maybe adding the second one is only for shielding, not for added magnetism. A steel cap is also used in addition to a bucking magnet. The strength of the bucking magnet is not as strong as the strength of the main magnet so the...
  16. audioguru2

    Speaker Magnet

    I don't think so.
  17. audioguru2

    Speaker Magnet

    A second magnet can add to the magnetism of the first magnet instead of using a bigger magnet. If the second magnet is physically reversed then the speaker becomes shielded with a very low external magnetic field.
  18. audioguru2

    Need help for Infra red tx Rx

    Each of your IR receivers must respond to its own code that is transmitted to it. Then it ignors the codes for the other receivers.
  19. audioguru2

    Need help for Infra red tx Rx

    An IR remote control unit for a TV does not transmit different frequencies. It transmits different codes.
  20. audioguru2

    Please help me in debugging the circuit!

    T1 is so poorly biased that it might be saturated, cutoff or linear. The collector of T2 is connected to ground. It should be connected to +5V. The emitter of T2 should have a resistor to ground. T2 is also poorly biased.
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