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  1. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Since the oscillator will be used in a superheterodyne FM radio that probably has a 10.7MHz IF, it must tune from 77.3MHz to 97.3MHz or tune from 98.7MHz to 118.7MHz.
  2. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Why did you add C4?
  3. Audioguru

    Lady bug robot

    Google shows a few Lady Bug Robot kits. They use infrared to avoid obstacles in its path. The kits probably show a block diagram and a schematic.
  4. Audioguru

    How to wire tweeter to speaker

    Speakers or tweeters in series are bad so use a capacitor in series with each tweeter. Look at the datasheet of the tweeter to see its recommended crossover frequency. It is easy to calculate a crossover frequency, 2.2μF in series with 4 ohms is 18.2kHz which is much too high. Use 15μF for a...
  5. Audioguru

    How to connect tweeter with speaker, series or parallel?

    Of course a piezo tweeter does not heat when connected to DC, it is not a coil of wire like a dynamic speaker, instead it is a crystal capacitor that draws no DC current. The sides of it flex and produce a click with DC or the sides vibrate when it is fed AC.
  6. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    If the varactor diode is connected backwards then it is not a variable capacitance part any more. Here is how it should be connected. I am glad to hear that you built the circuit instead of simulating it because maybe your sim program does not know that a varactor diode changes its capacitance...
  7. Audioguru

    How to connect tweeter with speaker, series or parallel?

    I have never used a piezo tweeter but the ones I have heard shriek badly and sound awful. Since they do not conduct then if one is connected in series with a woofer then the woofer will do nothing and maybe pass low and mid frequencies to the piezo tweeter and the inductance of the woofer will...
  8. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Did you use the schematic from WHONOES in post #71? Is your varactor diode connected with the correct polarity? When you vary the DC voltage V3 through R6 then does the frequency of the oscillator change?
  9. Audioguru

    Need Help With 12v Darkness Detector

    Like I said on the other forum, of course the LEDs will not turn off because the 2V from the solar panel is not enough to turn off the PNP transistor. The voltage from the solar panel must be about the same as the emitter of the transistor, 12V or 9V depending on the battery voltage.
  10. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    School kids make mistakes all the time. These Swedish kids say they used a Clapp oscillator but it is different to the one used in a Analog Devices applications note I found. I went to school such a long time ago that I can't remember a Clapp oscillator and I have never used one. My first solid...
  11. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    WHONOES, what is the signal V2 on your schematic that feeds the inductor through the tiny-value 100 femto-Farads capacitor C5?
  12. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    There is no "source". Your words are confusing, please post your newest schematic instead.
  13. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    Cc is obviously already on your schematic as C3, 100pF. Co can also be 100pF. What is the pulse V3 used for? It might short the capacitance of the varactor diode to ground. Didn't you notice that WHONOES shows your R5 as 10k. Since it is taking you weeks to make this simple oscillator then it...
  14. Audioguru

    I can't find any website will tell me what my transformer goes to or is good for

    18V at 5W is a current of 278mA. I do not know anything that uses 18VDC. It is cheap and is not worth adding a regulator to reduce its voltage.
  15. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    I see that the tuned LC is still wrong as a series resonant instead of as correct as a parallel resonant.
  16. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    How should he fix his broken spelling and broken grammar?? Maybe his translation software is broken?
  17. Audioguru

    Audio Amp vs Op-amp?

    The TDA2005 is a power amplifier to drive a low impedance speaker with plenty of current to make lots of loudness. When the power amp produces lots of power in a speaker then the power amp gets hot so its case has a metal tab that can be bolted to a heatsink. With an output power of 20W the...
  18. Audioguru

    Hello, can somebody help wich transistor is like bfg520

    C1 is an electrolytic capacitor that has too much inductance for it to work at the high radio frequency.
  19. Audioguru

    Infrared headphones idea help please

    I do not know the radio frequencies used by language translation IR receivers. There are many languages so there are probably many radio frequencies.
  20. Audioguru

    Infrared headphones idea help please

    Any half-decent product that transmits an FM audio signal and any half-decent FM radio together produce no hissing noises. But cheap Chinese junk from ebay is not half-decent, instead it is hissing garbage. Expensive and high quality IR audio receivers with headphones output are used at huge...
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