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  1. audioguru2

    My amp's distorting

    This amplifier is for only one channel. You will need a 2nd amplifier and speaker for the other channel. Maybe you have the input from the MP3 player connected so this amp plays the difference between both channels that sounds weird. Do You have a 4 ohm speaker connected at pin 4 and pin 6...
  2. audioguru2

    Inverter Circuit 12V DC to 230VAC Sine Wave

    Hi Grateful, The 220VAC sine-wave should be 622Vp-p, not 440Vp-p. An RC filter wastes a lot of power and needs a huge capacitor, an LC filter doesn't. An RC filter filters at only 20dB per decade of frequency, an LC filter filters at 40dB per decade of frequency.
  3. audioguru2

    Volume Control POT. . .

  4. audioguru2

    Volume Control POT. . .

    There isn't any difference. Dual 10k to 100k with an audio taper (logarithmic). Its power rating doesn't matter.
  5. audioguru2

    key finder

    The project is here: http://www.electronics-lab.com/projects/misc/002/index.html It has a full description of its circuit. What don't you understand about it?
  6. audioguru2

    ohms testing

    He wants to measure down to 0.01 ohms. The leads on my digital multimeters measure 0.3 ohms which is 30 times higher.
  7. audioguru2

    VU meter

    You said the LED stayed on. The PNP transistor is missing a resistor to turn it off. 6 inches of wire is a good antenna for interference pickup. The input wire must be a shielded audio cable. 22ms is a short blink. Try reducing the value of the capacitor for a shorter hold time then the LED...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Herman, I didn't re-design this project, I just fixed its errors that members complained about. In addition to the 2N3055, 2N2219 and main rectifier diodes "going up in flames", the opamps with a supply voltage higher than their max ratings and a transformer voltage too low, I have...
  9. audioguru2

    DC to AC

    I can't remember if the fluorescent lights used an inductive ballast or were the new compact fluorescent bulbs with an electronic ballast. Probably both.
  10. audioguru2

    Volume Control POT. . .

    The volume control doesn't need to be 10k. It can be any other value up to about 100k. Digikey in the USA has the same pot but it is 20k and 701 of them are in stock today. Part number P2U4203-ND.
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    The schematic is correct. The parts layout shows the pins of the original 2N2219 transistor for Q2. You must also look at how the original Q1 has its pins.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes, a Japanese D1691 is also fine when used as Q1 and Q2 in this project, if its pins are connected correctly (it has a different pinout) and it has a heatsink for Q2. There must be hundreds of transistor numbers in the world that will also work fine.
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    A Japanese 2SC3851 is identical to a TIP31A. Sorry, I couldn't find spec's for a D1691.
  14. audioguru2

    25W Mosfet audio amplifier

    Hi Bane, I'm glad you found its pcb.
  15. audioguru2

    DC to AC

    Our 500W square-wave inverter project was fixed and used in The Philippines to power incandescent and fluorescent lights, and multi-voltage TVs. It uses cheap 2N3055 transistors because power Mosfets were not available. I think the square-wave would cause trouble with transformers and...
  16. audioguru2

    project help with toy IC boards

  17. audioguru2

    Making a 0-28VDC@0-3A Power Supply using linear regulators (LM350)

    Look at our 30V variable power supply project. It uses a fixed power resistor to sense the current outside the voltage regulator so it doesn't cause a reduction of voltage regulation. Then it uses an ordinary inexpensive low power pot to set the reference voltage for an opamp that regulates the...
  18. audioguru2

    25W Mosfet audio amplifier

    Coupling capacitors cut low frequencies: 1) The 470nF value of C1 causes the output to be -3dB (half power) at 7.2Hz. If it is replaced by a 1uF film cap, the output will be -3dB at 3.4Hz and about -1dB at about 17Hz. 2) The 100uF value of C7 is fine. It causes the output to be -3dB at 3.4Hz.
  19. audioguru2

    Miniature FM transmitter modifications

    Hi Metro, The original Miniature FM Transmitter circuit that you posted looks like the one that somebody said didn't work with a new battery and didn't work when its battery is a little used because its audio transistor is incorrectly biased. I made it and fixed it and made it better until it...
  20. audioguru2

    Making a 0-28VDC@0-3A Power Supply using linear regulators (LM350)

    If R3 is in series with the load then the voltage drop across it will change when the load current changes resulting in no voltage regulation. Even the 0.1 ohm shunt resistor for the current meter degrades the voltage regulation to a 150mV drop with a 1.5A load. The LM317 without the 0.1 ohm...
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