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  1. Audioguru

    Transistors

    Bill999, you do not say where you are and if you will use Japanese, European or American replacement transistors. Look at the pinouts on their datasheets to see that they are different in those different worlds.
  2. Audioguru

    I want to make clear sound of the woofer speaker.

    A capacitor marked "104" is 0.1μF or 100nF. If the woofer is 8 ohms then this capacitor in series will pass only frequencies of 200kHz and higher that you cannot hear. If you connect the capacitor parallel with the woofer then you will not hear any difference than without the capacitor. Your...
  3. Audioguru

    Transformer for Camera

    A transformer produces AC that is completely different from the DC needed by the camera. The DC must have a connector with the correct + and - polarity.
  4. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    I guess the TV is built to produce hum from its internal speaker amplifiers when it is in standby mode and its amplifiers are not powered.
  5. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    You show a shielded audio cable from the TV low impedance output to the low impedance headphones. The low impedance does not pickup hum and interference. You are assuming that the balck speaker wires are gronded together but we keep telling you that the balck wires are probably bridged and must...
  6. Audioguru

    Solar Drone

    Your little battery powers an oscillator that drives a voltage boost converter.
  7. Audioguru

    Solar Drone

    How will you increase the 0.5V to 5V? A silicon transistor needs at least 0.7V to 1V. Oh, 4.7W can heat some water to drive a steam engine that turns a generator. Maybe the little battery can power a voltage stepup circuit.
  8. Audioguru

    Solar Drone

    Why don't you use a solar panel that already produces the 5V to feed the battery charger? A 5V solar panel has 10 solar cells in series. If it is rated at 4.7W then its current will be about 940mA and might quickly blow up your little battery.
  9. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Yes the display has about 46 LEDs and each LED uses about 5mA -10mA of current. A balanced charger adjusts the charging voltage on each cell so that the weakest one does not over-charge and blow up (Lithium is combustible when over-charged). Here is what happens if you buy a cheap Chinese...
  10. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    The wiring diagrams look confusing. Why do Chinese people call a wire a "line"? The yellow wire measures the positive voltage and the current is measured in series with the negative of the power supply and the negative of the load (but why with a red wire?). I don't know if the display uses...
  11. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Try using your 25W/12V= 2.1A soldering iron as the load. Since it is a heater then its resistance is less when cold so it might draw more than 3A then the project will not work. Try it with the voltage set to 10V. Most digital meter products need a power supply that is completely separate from...
  12. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    7.5k with 30V across it uses a current of only 4mA which is too small. Five 7.5k in parallel use a 30V current of only 20mA which is also too small. If your BD139 and output transistor are on heatsinks then first try a load of 100 ohms/12W or 15W to make a current of 300mA at 30V.
  13. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Good, U2 works properly. R2 was glowing red hot on the original Greek kit because it was only 1/4W. It is 2W and fairly warm on my parts list and should be fine. Time to connect the BD139 and output transistors? Use a load resistance because it doesn't have anything.
  14. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    Good, pin 2 voltage is normal. Also check that its pin 3 can go from almost 0V to +1.41V when adjusted by the current setting pot P2. Pin 5 is not used in this circuit. Now see if the output from pin 6 of U2 can go from 0V to about +34V (adjusted with the voltage setting pot P1) when it is...
  15. Audioguru

    Chinese Hiland 0-30V/Audioguru PSU build (down the rabbit hole)

    I am glad that you discovered the problem with the -1.3V. Pin 6 of U3 is at a normal high voltage which prevents the current regulation from limiting the output voltage through D9 and it also turns off the LED. But pin 2 should be almost 0V since R7 is only 0.47 ohms connecting its R21 to 0V...
  16. Audioguru

    Tone for thought..

    Manufacturers of amplifiers for electric guitars use an input impedance of 1M minimum with a vacuum tube or Jfet. I hope your tone controls circuit does not have a lower impedance that will "smother and muffle" the output of your electric guitar.
  17. Audioguru

    Who knows how to test N-Ch. MOFETS with Multimeter? Please HELP!

    It is much better than using a digital multimeter that does not produce enough voltage to turn on a Mosfet.
  18. Audioguru

    How to drive NMOS (IRF540n) from PWM?

    You need a push-pull output. Two of the same kind of Mosfets can do push-push or pull-pull but cannot do both. An IRF540 or IRL540 is N-channel that has a drain that can go down to ground but it does not go positive. A P-channel Mosfet is needed for its drain to go up to the positive supply. The...
  19. Audioguru

    powering camera with usb battery

    Lithium burns violently. If you connect 5V USB to a 3.7V lithium battery then it will overcharge, explode and catch on fire.
  20. Audioguru

    Bypassing TV's internal speakers to home-made aux input

    All audio products come with shielded audio cables for connecting products together, but speakers do not use shielded cables. Sine I have a box full of shielded audio cables I have not tried to use Mickey Mouse aluminum foil and try to connect it to the ground wire.
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