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  1. audioguru2

    indulis or Audioguru?

    Before the Spammers took it over, our High Voltage forum was full of stepup circuits that use a stepup transformer, not an untapped inductor. I am just an audio guy who never made a Telsa Coil nor high voltage stun gun. Then I answered the post with a lot of maybes that would have resulted in...
  2. audioguru2

    FM Micromitter only transmitting 8M

    The pcb layout for the regulator is correct. No, sorry.
  3. audioguru2

    FM Micromitter only transmitting 8M

    Hi David, Maybe your 78L05 voltage regulator is installed backwards or is damaged. Remove all 3 resistors of the attenuator for best range. Your antenna's length is correct and if it is vertical then it radiates all around, then the receiver also must also have its antenna vertical. A dipole...
  4. audioguru2

    Digital 7 segment clock with trigger

    Hi Francois, Pick a clock circuit that doesn't multiplex the display. An electronic clock doesn't have an output that gives a pulse each minute. You would need to take a signal from each segment of the lowest minutes digit and capacitor-couple them to an OR gate. Then make a 2-seconds monostable...
  5. audioguru2

    What is the DC resistance of an inductor?

    The resistance of an inductor is the resistance of its wire. Measure its resistance or calculate it from a wire table. The wire table lists the resistance of each wire size for a certain length.
  6. audioguru2

    FM Micromitter only transmitting 8M

    Pin 8 of the IC should be 5.0V which is the output of the 78L05 voltage regulator or the 6V battery voltage. If you use the voltage regulator and D1 in series with it, then the minimum input voltage is 8.2V. Don't use a 9V battery because its voltage quickly falls lower. The micromitter has an...
  7. audioguru2

    Transformer Questions!!! ???

    An overloaded transformer could buzz and is dangerous. A buzz noise from a normally operating transformer is an indication of poor quality. It might have other more serious and dangerous faults. Return it to the store for replacement or throw it away and replace it with a better one.
  8. audioguru2

    Bass guitar effect pedal (need help)

    The article with the LM386 shows a high input impedance FET buffer from the guitar to the LM386 amp. If you play strongly then the high output from your guitar could overdrive the FET, the input of the LM386, the output of the LM386, the circuitry in the effects unit or the power amplifier...
  9. audioguru2

    50Hz when you touch Oscilloscope probe

    Hi Zeppelin, An elsctrostatic field works with AC or DC. There is a very small amount of capacitance from nearby mains wiring and your body. There is a small amount of capacitance to ground at the 'scope probe. The capacitances are joined in series at your body and make a capacitive voltage divider.
  10. audioguru2

    Low-pass Filter?

    Hi Xerex, I use www.datasheetarchive.com to get datasheets but 1st I need to know the part's number. The max supply voltage for a CD4047 is 18V. Use a 12V zener diode. The max supply voltage for an LM358 is 36V so it is fine with 24V. It needs to have a gain of 2 so its 12V input from the...
  11. audioguru2

    Yet Another Question on the 4W Transmitter

    Look closely at the pics and you will see 6 holes in the ferrite of the chokes. The one at the top shows one and one-half turns, but says two and a half turns. Get it so it fits on the pcb. Its impedance is fine. Be nice to the RF cops when they come after you. They might just give you a...
  12. audioguru2

    Yet Another Question on the 4W Transmitter

    Hi S_M, If you are really desperate then pay the high minimum order charge and get some VK200-3A from RF Parts. What are you going to do with this old 4W transmitter that will cause severe radio and TV interference, drifts its RF frequency all over the dial, is mono not stereo and sounds bad...
  13. audioguru2

    indulis or Audioguru?

    So I said that type of circuit "doesn't stepup the voltage very high" and you say it can but it is impractical so none are made that way? Then my statement is not totally incorrect. I should have said, "That type of circuit isn't used to stepup the voltage very high".
  14. audioguru2

    Transformer Questions!!! ???

    Which circuit? Very old audio amplifiers and new PA amplifiers use an output transformer. DC to AC inverters use an output transformer. The high voltage circuit for a camera's flash uses a transformer. Nearly everything electronic that is powered by the mains has a power transformer. A...
  15. audioguru2

    Electronic Stethoscope

    Hi TriGerminal, Your circuit motorboats and the LED doesn't light. So I think one or both of your batteries are dead. The circuit makes a little amount of noise that is amplified. When the opamp tries to drive current into the LED then the battery voltage collapses and the noise stops, then the...
  16. audioguru2

    50Hz when you touch Oscilloscope probe

    I think mains hum picked up by your finger or another antenna is produced by  electromagnetic and electrostatic fields. You are surrounded by mains wiring that transmits the fields so that's why I call it radiation.
  17. audioguru2

    indulis or Audioguru?

    Hi mik3ca, I have never seen a SMPS use a single untapped coil to stepup the voltage of a battery to a high voltage and gave examples of circuits that stepup the voltage not very high. Indulis said I was incorrect but didn't give examples showing why. In addition to the LED drivers I mentioned...
  18. audioguru2

    Electronic Stethoscope

    Hi TriGerminal, The circuit has high gain and could pickup interference from the air if it is not built compact on a pcb or on Veroboard or does not use a shielded audio imput cable. Your circuit produces a static noises and a low frequency oscillation called "motorboating". Does the LED...
  19. audioguru2

    50Hz when you touch Oscilloscope probe

    Hi Shahriar, Do you have a light dimmer? Turn it on to half then it radiates spikes you can see on a 'scope with your finger or another antenna on its input.
  20. audioguru2

    Sound Level Indicator

    The text of my project answers your questions: "4) Three 2N3904 transistors are used as emitter-followers: a) Q1 is inside the negative feedback loop of the 2nd opamp as a voltage reference for the other two transistors. Hopefully the transistors match each other. b) Q2 emitter-follower...
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