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  1. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Too Expensive, You probably can't measure it because the waveform will be distorted but what do you think is the modified transformer's voltage rating when your project has a 5ADC load? How many milli-volts DC does the output voltsge drop from no load to 5A load at 25VDC?
  2. audioguru2

    Adjustable Voltage Reg LM317, Should it be getting this hot ?

    Hi Nick, Your little heatsink is too small. The max internal temperature of the junction of the LM317 is 125 degrees C, the thermal resistance from its junction to its case is 4 degrees per Watt and you have it dissipating (12V-7.2V) x 1A= 4.8W, so if its case is at 106 degrees C then it is too...
  3. audioguru2

    CD4049 switching failing to switch

    Your 4049 circuit doesn't have a pushbutton. Its output doesn't connect to anything. I know that if a pushbutton is connected to J2 then the output will alternate each time the button is pressed. Is that how you have it? Your 555 has its pin 2 and pin 6 biased at half the supply voltage. Why...
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Change? Oh yes. The original project has poor performance and smokes its parts. I recommended a few changes to fix and improve it. Sorry, I don't have the circuit in Spice, I just look at it and know what the voltages are supposed to be. Many simulator programs don't know if they are coming or...
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Nekro, It is good to hear that D7 will survive. Your BD249 transistors are a lot better than the original old 2N3055. They actually have a good amount of current gain spec'd at their max of 25A. 2N3055 transistors have a lousy current gain spec at only half their max current. The OP07 has a...
  6. audioguru2

    series RC circuit

    Yes, and an RC network also causes a change of phase when the frequency changes. EDIT: Terrible English corrected.
  7. audioguru2

    series RC circuit

    Thanks, Cabwood. ;D Your explanation about how time and the rate of change on an RC circuit helps the understanding of how a phase-shift occurs.
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    The peak voltage of a 24VAC transformer is 34V and the diode bridge drops it to only 32.5V. It might be as high as 35.5V without a load but yours is extremely high and will damage the opamps. It is supposed to be negative 5.6V and the same at both opamps. Then U1 is not working, it should be...
  9. audioguru2

    Using the LM331 V-F Converter

    Hi Fowkc, Welcome to our forum. ;D The circuit goes down to zero Hz with a 0V input. The linearity is spec'd from 10Hz to 11kHz. You don't need a negative supply nor the offset adjust pot since you don't want zero Hz. Just bias the input and mix the input voltage with resistors so that when your...
  10. audioguru2

    FM frequency

    Your FM broadcast band radio is wideband. Communications is narrowband so if your radio has its frequency changed then the level of communications will be low and noise and interference will be high. How many tuned circuits does your radio have that will need to be changed then re-aligned? Of...
  11. audioguru2

    LED Timer

    LEDs need a fairly high amount of current. If they all turn on then the current is 10 times as much as if only the indicating one is on. Choose a circuit that lights only the indicating LED. Select very bright LEDs that need a very low operating current. Select low voltage (red) LEDs. Choose a...
  12. audioguru2

    series RC circuit

    The very low distortion sine-wave oscillator I made has harmonics at such a low level that is is nearly impossible to measure them. The strongest harmonic is the 3rd and it is at 1/50,000th of the output level. Most of the even-numbered harmonics are absent. I took a CD4018 Walking-Ring Counter...
  13. audioguru2

    series RC circuit

    A sine-wave is like a swinging pendulum. It starts slowly at a peak and gets faster then slows down and nearly stops, then repeats in the other direction. Its rate of change continuously and smoothly changes.
  14. audioguru2

    opamp phase compensation

    I don't know which circuit and i don't know which opamp you are talking about. Fully compensated opamps (a few are not fully compensated) are made with built-in frequency compensation that has 20dB/decade rolloff so that their gain is below 1 when their internal phase-shift would cause...
  15. audioguru2

    Wireless (Radio) Headphones

    You might be able to get the parts to make one and they are sold to transmit to a car radio. They are about the size of an MP3 player. You won't be able to make a good and small one. If somebody makes a small stereo receiver that works well then it is rare and will be very expensive.
  16. audioguru2

    series RC circuit

    The AC mode of a multimeter is made to measure the sinewave of the mains frequency. It is inaccurate at higher frequencies or with waveforms having higher frequency harmonics. A 'scope or AC millivoltmeter can accurately measure higher frequencies or waveforms with harmonics. A sine-wave is a...
  17. audioguru2

    opamp phase compensation

    I have no idea why you would want to short the high frequencies of the input signal to ground with a capacitor. Maybe the pcb is layed out with the input and output side-by-side causing capacitive coupling of high frequencies causing oscillation. Then a capacitor at the input shorts the high...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Nekro, Welcome to our forum. ;D The OPA37 is made for a closed-loop gain of 5 or more so it cannot be used for U1 nor U2 which have less closed-loop gain. It will oscillate at a high frequency unless the circuit is modified to use it. The OPA27 and OPA37 have diodes between their inputs that...
  19. audioguru2

    series RC circuit

    Hi Kevin, A triangle wave consists of many harmonics. The resistor passes them all at the same level. The reactance of the parallel capacitor is a lower impedance at high frequencies than the resistor so it passes the higher frequencies more than the lower frequencies. An RC circuit with the...
  20. audioguru2

    opamp phase compensation

    Hi Kevin, What is a phase compensation capacitor at an opamp's inputs? I have seen a capacitor added between inputs to stop the input transistors from rectifying a strong nearby radio signal. Most opamps have a built-in phase compensation capacitor. Because an opamp has a very high open-loop...
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