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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    Q1 was used when the opamps were TL081 because they had the problem called "Phase Inversion" where the output would suddenly go high when the input became within a few volts of the negative supply (that happens when the power is turned off). The TLE2141 opamps do not have this problem because...
  2. audioguru2

    Simulation of 12-Watt Amp Help

    No. The input voltage divider at the input with two 22k resistors sets the center node at 18V. The 2.2k voltage divider fed hum into the negative feedback input and messed up the voltage at the center node. The negative feedback through the 10k resistor from the output to the input of transistor...
  3. audioguru2

    Simulation of 12-Watt Amp Help

    Doesn't your schematic look awful with the dark green background covered in dots and with backwards and upside down transistors? I think the hum comes down the extra 2.2k resistor directly into an input. The extra 2.2k resistor is not needed because the right side input transistor is biased...
  4. audioguru2

    Simulation of 12-Watt Amp Help

    I fixed the schematic: 1) I removed the horrible dark background that was covered with dots. 2) I cropped it. 3) I straightened all the "dog legs". 4) I put the PNP transistors right side up and left to right. 5) I marked "X" on one useless resistor. EDIT: The 0.1uF capacitor in series with the...
  5. audioguru2

    0-30V Stabilized Power Supply

    Thenr, This project uses a 28VAC or 30VAC transformer. The rectified and filtered unregulated DC is +37.6V to +40.4V when the load is 3A, not just 24VDC. The circuit might need changes to operate from only +24V and the max output voltage will be about +18V or +19V. Go to www.farnell.com and...
  6. audioguru2

    Full sound bar schmatic/BOM

    I will not open a zipped file from somebody I do not know. This is his first post here. The file might be a computer virus!
  7. audioguru2

    Adding led brake lights

    It is an antique that is 44 years old and only used by old teachers today. The lousy old 741 opamp has inputs that do not work when they are anywhere near 0V or the positive supply voltage. Its output does not go low enough to turn off the transistor. It is too slow to follow the PWM pulsing. I...
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tompa, Since your current meter is in series with the load then its resistance reduces voltage regulation at the load. It will be better to use a voltmeter to measure the voltage across R7 which shows the amount of output current without reducing the voltage regulation. When the current...
  9. audioguru2

    help i want a 6-channel transceiver

    But a girl wearing a skirt will see and hear the camera robot coming. ::)
  10. audioguru2

    Electronic Music Box Project

    You should also learn about the 555 IC, its output is a square-wave. You should also learn that square-waves have an irritating sound like a buzzer or an amplifier with its volume turned up way too high. The loudness and frequency have nothing to do with the irritating sound. A flute has a...
  11. audioguru2

    12 V DC - 220 V AC (DC Flourecent lamp)

    You do not make sense. You want a schematic: For a 12DC fluorescent lamp? For a 12VDC to 220VAC inverter?
  12. audioguru2

    0-30V Stabilized Power Supply

    U1 has an output of +11.2V and its inputs are at +5.6V so it does not need a negative supply. U2 has an output that goes as low as +1.0V and has inputs that work at 0V so it does not need a negative supply. U3 is the current regulator. It works by reducing the output voltage so that the output...
  13. audioguru2

    Brightest White LED

    My cheap solar garden lights are EXTREMELY bright at night if you look at them. But they are not bright enough to light up anything nearby.
  14. audioguru2

    Internet Radio

    I usually listen to FM radio on my cable TV digital adapter connected to my new 2.1 powered speaker system. It is also used with my TV in my computer room. I should make a switch so my TV sound system can be used with my computer (my computer powered speakers sound pretty good but not nearly as...
  15. audioguru2

    Is it bad design?

    If the transformer is low quality (cheap) then its output voltage is very high when there is no load. I have a cheap AC-DC wall wart with a rated output of 9V/100mA and its output is correct. But without a load its output is 19VDC. The 1k resistor R3 provides a load when there is no other load...
  16. audioguru2

    Brightest White LED

    Many cheap "bright" LEDs are for sale but they are simply a dim one in a case that focusses the light into a very narrow but bright beam. Good LEDs have the same brightness or more and have a wide beam angle.
  17. audioguru2

    Electronic Music Box Project

    The electronic organ uses a squarewave generator IC. A squarewave sounds like a buzzer. A completely different circuit can make a sinewave that sounds like a flute or make a triangle wave that sounds something like a violin. The piezo beeper in the bell circuit creates a tone at the resonant...
  18. audioguru2

    Why caps in paralell?

    25pf is not a standard value. 10pF, 15pf, 22pF and 27pF are standard values.
  19. audioguru2

    0-30V Stabilized Power Supply

    A coarse pot and a fine pot would be a nuisance. The fine would almost always be in the wrong position. Use a bigger knob instead on one pot.
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    You built the original project that used old parts that were overloaded so it is not reliable. This improved version uses modern parts operating within their maximum limits.
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