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  1. Audioguru

    Ebike battery

    YouTube has videos of cheap ebay Lithium batteries taken apart and showing flour inside instead of battery chemicals. A battery advertised by AliExpress shows its impossible 9900mAh rating. Look at its very low price.
  2. Audioguru

    Understanding signals in PWM

    Usually the carrier triangle wave frequency is much higher than the sinewave modulation frequency.
  3. Audioguru

    Ebike battery

    AliExpress sell fake 18650 batteries like the other Chinese places with "sellers".
  4. Audioguru

    Phase Shift Oscillator Puzzle

    As i suspected, your resistor values are Way Too Low for a low power CD4069 Also its gain is trying to be 2000 times with the extremely low 500 ohms value for the input resistor instead of about 27 times using a 33k resistor. I thought you wanted to make a sinewave but your circuit with digital...
  5. Audioguru

    Understanding signals in PWM

    A PWM sinewave is made by using a comparator with a triangle wave as the high frequency carrier frequency and a pure sinewave as the modulation frequency. Then the output of the comparator has pulses with widths according to the comparison. PWM has square waves only when the modulation is 50%...
  6. Audioguru

    Understanding signals in PWM

    Your signals are not Pulse Width Modulation because all your pulses have the same width. Instead it is Pulse Position Modulation but as shown in the datasheet of an LM555.
  7. Audioguru

    Phase Shift Oscillator Puzzle

    Why don't you post your schematic that might have resistor values that might be much too low? Did you feel the temperature of the 74HC04 and measure the DC current of the circuit?
  8. Audioguru

    Phase Shift Oscillator Puzzle

    Yes, your oscillators use highpass filters. Here is one that uses lowpass filters. The amplifier gain must be about 27 times because the filters are not buffered and affect each other. The output needs a high impedance load.
  9. Audioguru

    Phase Shift Oscillator Puzzle

    The digital inverter oscillator should work when made like this:
  10. Audioguru

    Substituting a Capacitor

    Nano-Farads are nF. Micro-Farads are uF. 1uF is 1000 times more than 1nF. Your 47uF capacitor is 100 times more than the 470nF that you need.
  11. Audioguru

    Another Newbie question about Power supplies

    This is from Duracell's datasheet:
  12. Audioguru

    Another Newbie question about Power supplies

    Energizer makes 9V alkaline batteries and show a datasheet. It shows the voltage dropping with time when powering a 270 ohm load. You can simply calculate the current that is also dropping by using Ohm's law. If the resistance is lower then the current is higher and the time is shorter.
  13. Audioguru

    Need help understanding this circuit

    The video (from India?) shows an 8 ohm speaker at 8:00 in the video not working because the 555 ICs are not powered.
  14. Audioguru

    Need help understanding this circuit

    With a 9V supply and an 8 ohm speaker connected directly to the output of an LM555 or NE555 then the current will be so high that the 555 will burn out. But it will be OK if an ordinary 9V battery is used because that little battery will not be able to provide enough current to do damage.
  15. Audioguru

    Wind Detecting Circuit

    My city measures the wind at various locations and my Google Home Assistant tells me the wind speed and direction. Wind detector? Isn't that a "Phart" detector?
  16. Audioguru

    Circuit Soldering question

    The same as mine, even the same temperature.
  17. Audioguru

    Circuit Soldering question

    A cheap soldering iron has no temperature control (or maybe a useless lamp dimmer circuit to turn down its heat too low) so it gets hotter and hotter until it smokes away the important rosin in the solder causing poor soldering. My soldering iron is over 50 years old and has temperature control...
  18. Audioguru

    TDA2030a Amplifier I.C. Specs

    The tubes lasted but soon caused distortion and reduced levels. Hams and bombers didn't care about distortion. Audio tubes in those days were cheap and were sold everywhere (corner convenient stores) because everybody needed to replace them over and over. The tube testers in the stores were...
  19. Audioguru

    TDA2030a Amplifier I.C. Specs

    I made a Heathkit tubes amplifier in 1962. It used Williamson output transformer circuits and sounded pretty good when the tubes were new but they wore out and needed replacement every 3 months. I replaced it in 1964 with a Scott solid state stereo receiver that I still use today in addition to...
  20. Audioguru

    Touch Control Circuit

    All the other forums CLOSE old threads but not here.
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