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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    The 24VAC transformer has an output voltage too low for this power supply to produce 30VDC at 3A. The regulation will fail and there will be lots of ripple in the output at and above about 25V at 3A. I recommended a 28VAC or 30VAC transformer and higher voltage opamps years ago. For an output...
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    The TIP31 is 83 times slower than the BD139 that I recommend that has almost the same speed as the original 2N2219 that got too hot as Q2. Then the TIP31 will probably cause oscillation. 
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    Opamp U2 has a DC voltage gain of typically 200 thousand and its negative feedback connects directly to the output with R12. The negative feedback sets the actual gain at 2.68 times so if the output tries to decrease 1V then the actual output decrease will be only 13.4 micro volts which is...
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Lots of people made pcb designs for this modified circuit. I did not use one and I did not look at them. Sorry, I also did not look at yours.
  5. audioguru2

    How to make Audio power Amplifier Circuit

    The output of the voltage regulator and positive supply for the LM386 and Arduino all need a capacitor to ground to prevent oscillations.
  6. audioguru2

    How to make Audio power Amplifier Circuit

    You talk about adding a resistor to make the transistor amplify but it reduces the signal and you do not say the value of the resistor. Of course it will not amplify if the resistor value is calculated wrong. What value did you use for the added collector resistor? The inverter was completely...
  7. audioguru2

    How to make Audio power Amplifier Circuit

    Here is another Circuitspedia circuit that has serious errors. Also, its text says to use a 3V to 6V supply but the datasheet for its LM386 says that its minimum supply is 4V or 5V.
  8. audioguru2

    How to make Audio power Amplifier Circuit

    I am showing a CORRECTED audio amplifier circuit and a CORRECTED simple inverter circuit:
  9. audioguru2

    How to make Audio power Amplifier Circuit

    The circuit shown is a block diagram, not a schematic. The inputs and outputs of the opamps are not shown and the collectors, emitters and bases of the transistors are not shown. An important capacitor between the positive and negative power supply pins of the IC is missing. Diodes or a...
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original old Greek kit used TL081 opamps that have a problem called "Opamp Phase Inversion" where the output goes positively as high as it can if an input voltage gets within a few volts from its negative supply voltage. The improved project used newer opamps that do not have this problem...
  11. audioguru2

    LED Flasher Chaser Circuit with or Without IC

    Using a single color red LED: A CD4017 powered from 9V can output 16mA into a 2V red LED on each output which is enough to burn out its output transistors. Use 150 ohm series current-limiting resistors to share the heat. 
  12. audioguru2

    FM Transmitter

    The frequency of FM broadcasting is high enough so that the signals go straight and far if there is nothing blocking them. But the curvature of the earth blocks distant reception. Of course the range depends on the transmitting power and direction, and the sensitivity and direction of the...
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    How can you use an LM339 without reading its datasheet? Since its output is "open collector" then it cannot turn on the transistor unless you add a "pullup resistor". The output of your 10A rectifier does not connect to "regulator in". Instead it has a huge filter capacitor (12000uF) and it...
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Each comparator in an LM339 has an output current of only 4mA. Relay coils need more current so transistors or Fets must be in between. Your block diagram is missing the huge filter capacitor needed that might burn out the relay contacts when the relays switch taps.
  15. audioguru2

    Help with a simple lm317 circuit

    You should always read the datasheet for an electronic part to see what is needed and why. The datasheet for an LM317 shows an input to ground disc capacitor of 0.1uF and an output to ground electrolytic capacitor of 25uF or more. The datasheet shows the more expensive LM117 that can use a...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    Simply test voltages in the circuit with a voltmeter. The opamp U2 controls output voltage regulation and it has an extremely high internal voltage gain (220 thousand times for a TLE2141). The negative feedback of the circuit detects any output voltage loss and directs U2 to correct it. I...
  17. audioguru2

    Help with a simple lm317 circuit

    You forgot to attach your schematic so we can see the resistor values and important input and output capacitor values. Maybe the wallwart has very poor or no filtering then its "12V" is fluttering, averaging a voltage much less than the minimum of 5V that the LM317 needs. Maybe the wallwart is...
  18. audioguru2

    battery level indicator

    The LM3914 in a DIP case is not made anymore. Buy them before they are all gone.
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original defective circuit had many overloaded parts that will blow up. The improved version fixes it. Opamp U3 senses the output current in R7 and reduces the output voltage and output current to match the current set with P2. The maximum output current is 3.0A in the improved circuit and...
  20. audioguru2

    How to connect Condenser microphone with any amplifier

    No. An old condenser mic uses 48V and needs a preamp with a very high input impedance. It does nothing in your circuit. A modern electret mic (look it up in Google) is a condenser mic with 48V stored permanently in its electret material and has a Jfet inside that has a very high input...
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