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  1. audioguru2

    BJT biasing formulas

    Hi friend Walid, I'm sorry you don't understand me, I'm not a teacher nor an author. Each part number and each sample of transistor has a different current gain. Transistors have very reduced gain at high currents. Therefore I calculate the current in the voltage divider to have about 10 times...
  2. audioguru2

    What does it mean when the voltage lower it self up?

    Hi LegendBreath, You project isn't crappy, but your transformer might be. What is the voltage at the input to the regulator without a load? If you have three 47 ohm/1W resistors, connect them in parallel across the output of the regulator as a load, then measure the input and output DC voltage...
  3. audioguru2

    What does it mean when the voltage lower it self up?

    Hi LegendBreath, How much current is your regulated 6VDC output going to supply? What is its load? We are afraid that your big, little transformer can't supply enough current without its output voltage dropping too low. Also it might overheat if it is overloaded. The regulated 6V output might...
  4. audioguru2

    BJT biasing formulas

    Yes sir, teacher Alun! ;D I also had confusing teachers when I was is in school. I wonder why Autir doesn't learn this basic stuff in school. ???
  5. audioguru2

    help me with this computation

    Hi Nolram, Welcome to our forum. ;D We have two Digital Volume Control projects. Which one are you talking about? http://www.electronics-lab.com/projects/audio/010/index.html http://www.electronics-lab.com/projects/audio/033/index.html The 1st one doesn't have a debounce circuit for the...
  6. audioguru2

    transformer parts

    Hi DocOc, Welcome to our forum. ;D You are talking about 6600W you know. That's a lot of power, and a 12V car battery will blow-up with the circuit's 550A from it. What are you going to use to switch 550A into a transformer to step it up to 300V at 22A? If you ever manage to get 300V at 22A...
  7. audioguru2

    Laser Link Communicator

    Try it with your 10 ohms NTC in series with a 56 ohm resistor, and don't let the ambient temp change very much. Of course, all diodes have polarities. Look at its pic in its datasheet.
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes. I think this will work:
  9. audioguru2

    high voltage photo flash capacitor charger

    Capacitors have a parameter called "dielectric absorption" which causes a voltage to develop across them after they have been discharged. Electrolytic capacitors especially have this problem. It messes-up the biasing of transistors or opamp circuits which causes distortion.
  10. audioguru2

    Ignition coil driver circuits and experiments

    The bottom one in your stack of them develops a voltage from the heavy weight on it! ;D
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Cyw, The output of U1 is an 11.2V voltage reference, and the pots just divide it down. The voltage range is easy to calculate. However, the lower end of R17 has the voltage developed across R7 (caused by output current) adding a negative voltage to R17. To use another control voltage instead...
  12. audioguru2

    BJT biasing formulas

    Hi Alun, Eek! Horrors! No emitter resistor? No resistor from the base to ground? For your simple circuit you must select a transistor with a gain of exactly 100 and don't allow its temperature to change. You also must feed it from a very low source impedance and ignor its high distortion.
  13. audioguru2

    BJT biasing formulas

  14. audioguru2

    Reduce DC voltage, How? please..

    The more expensive LM117 uses 240 ohms for R1, the cheaper LM317 is supposed to use 120 ohms. Its current holds down the output voltage without any other load.
  15. audioguru2

    Mosfet Latching

    The original circuit has an IRF510 N-channel Mosfet.
  16. audioguru2

    What does it mean when the voltage lower it self up?

    Why is a little 2"x 2"x 2" transformer considered to be "big"? Was it from a 2W boom-box stereo? ??? ???
  17. audioguru2

    What does it mean when the voltage lower it self up?

    Hi Alun, Thanks, I was calculating for 6VAC in error. :-[ Actually, his 7VAC will probably be much higher unless he is overloading the transformer or operating it at its limit. You know what? I bet it is a 5VAC winding when loaded, but he measures 7V without a load. Then the DC input to the...
  18. audioguru2

    Mosfet Latching

    The best way to add some positive feedback in that circuit would be to swap the comparator's inputs and turn upside-down the pot and its resistors. ;D
  19. audioguru2

    Mosfet Latching

    Yeah, it might be better to use an LM311 comparator in that circuit but it might oscillate at the zero crossings. A TL071 opamp would also work pretty well, wouldn't oscillate, wouldn't need a pull-up resistor on its output, is a little cheaper and slews almost the speed of an LM311 comparator...
  20. audioguru2

    MODERATOR!

    I sold mine a while ago. ;D
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