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  1. audioguru2

    audioguru fm transmitter

  2. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    The 500W inverter won't work with an amplifier. The M250 amplifier can be used in a sine-wave inverter. If you use 8 car batteries in series to feed it positive and negative 48V, its output power will be only about 115W to about 200W and can be used with a 30VAC stepup transformer.
  3. audioguru2

    Headlight Flasher

    You must select a relay and transistor to match the current of your headlights and all the other things I mentioned. You also must select whatever parts you can find in your country that have those spec's.
  4. audioguru2

    audioguru fm transmitter

    Increase your battery's voltage to 9V and the range will be much farther. Also, decrease the value of the 470 ohm resistor to 220 ohms. The antenna should be about 80cm long, in the same direction as the radio's antenna. The radio should also have an 80cm long whip or 160cm long folded dipole...
  5. audioguru2

    sending a beep into the telephone line???

    Relay for isolation, coupling capacitor to block DC, resistors to adjust the tone's level and to match the impedance and protection diodes:
  6. audioguru2

    Headlight Flasher

    This project? http://www.electronics-lab.com/projects/automotive/003/index.html The current rating of the relay contacts must be at least as high as the headlamps' current plus more, since a cold incandescent lamp draws up to 10 times its operating current. The current rating of the transistor...
  7. audioguru2

    audioguru fm transmitter

  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes, then Q3 would never turn off. The output of the opamp U3 is a darlington transistor and its max voltage is about 1.5V lower than the positive supply. Yes, I had it backwards.
  9. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    I don't know which transistors you can buy in your country. The output transistors in the schematic I posted have only one of them available at an American distributor.
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes, I had it backwards, you are correct.
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    C2 is charged through the rectifiers on half-cycles from the transformer, then discharges a negative current which makes  the negative supply.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Is C2 47uF (maybe it is open) and is it installed with the correct polarity? Is R2 82 ohms? Is one wire of the transformer shorted to 0V?
  14. audioguru2

    audioguru fm transmitter

  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    R2 has AC on it. I don't know what DC measurement will be shown on a meter. Maybe C2 is open. Maybe D5 is shorted. Measure these voltages with the negative meter lead connected to the negative terminal of C1.
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    R9 feeds the adjusted reference voltage to U2 and limits the loading effect of C4 on the output of U3. If its value is higher then U2 might pickup interference. If its value is lower then U3 might oscillate due to C4 being at its output or R9 won't discharge C4 quick enough during current...
  17. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    A class-AB amplifier is about 50% efficient at clipping, so a stereo amplifier with 144W output from each channel will have a supply power requirement of 576VA which is a current of 7.6A. Amplifiers don't work at full power continuously so a smaller transformer with a current of 5A will be fine.
  18. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    Your transformer has a sine-wave RMS value of 28VAC. Its peak voltage is 28 x 1.414= 39.6VDC. The two rectifier diodes in series will drop it to about 37.6VDC at full output which is far less than 55VDC. At clipping, the amplifier will make a sine-wave at its output of about 69Vp-p which is...
  19. audioguru2

    confused about voltage regulator spec

    You can overload or short the output of a regulator. It will limit the current, get hotter and hotter and if the heatsink isn't big enough then the regulator will shut down. After it cools it will begin working again. It isn't recommended to leave a regulator cycling like that because of the...
  20. audioguru2

    Stereo Audio power amplifier 2 x 40W - 80W

    Making a high power amplifier with high voltage transistors and with them paralleled for high power is a waste if you use your little transformer that has a low voltage. The amp will have the same low power as the other amplifier that uses this little transformer.
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