Search results

  1. audioguru2

    0-30V Stabilized Power Supply

    The opamps should draw only a small amount of current from the negative supply. Your U2 or U3 opamp draws too much. Find it and look at how it is connected wrongly. R7 should be 1.92V/3A= 0.64 ohms. The original project had a max putput current of 1.92V/0.47 ohms= 4.1A which is too high. We use...
  2. audioguru2

    0-30V Stabilized Power Supply

    You have a serious problem with your -5.6V supply. Replace R2 and C2.
  3. audioguru2

    0-30V Stabilized Power Supply

    R16 bypasses any leakage current in Q4 when it gets hot to turn it off when it is supposed to conduct a small current. D10 discharges C7 when the output voltage suddenly is reduced and there is no load.
  4. audioguru2

    0-30V Stabilized Power Supply

    No. Remove only Q1, R13 and R14. Yes.
  5. audioguru2

    0-30V Stabilized Power Supply

    Q1 is used when the U2 opamp is a TL081. Q1 is not needed when the U2 is almost any other opamp. I think your Q1 is turned on all the time because something is wrong with your negative -5.6V supply. With Q2 disconnected, R16 should turn off Q4. The collector of Q4 is supposed to be connected to...
  6. audioguru2

    0-30V Stabilized Power Supply

    You have the latest parts list but the latest schematic  and pcb are different to the original one. Here is the latest schematic that goes with the parts list you found.
  7. audioguru2

    0-30V Stabilized Power Supply

    U2 has a variable input voltage of 0V to +11.2V from the voltage adjustment pot. U2, Q2 and Q4 make an amplifier with a voltage gain determined by R11 and R12 so the gain is 3.074 times. Q2 and Q4 are emitter-followers with a base to emitter voltage of about +0.7V when the load current is low so...
  8. audioguru2

    Efficient telephone audio (300-650Hz) fedback mechanism !!!

    Please post your schematics here[/]b] instead of over at SCRIBD that takes all day to wake up. You have a value of 10k for R5 that creates high attenuation of your audio sound signal.
  9. audioguru2

    A battery of batteries... good idea or bad?

    Maxim have battery charger ICs for charging Ni-MH cells in series. Each cell is 1.4V to 1.5V when fully charged so the charger must be able to produce 12 x 1.5V= 18V. The battery voltage will average 1.25V per cell when discharging which is 15V total. You must detect and disconnect the battery...
  10. audioguru2

    AC-DC Inverter Circuit Principles

    PWM has a high frequency square-wave that has its duty-cycle changed by the 50Hz or 60Hz sine-wave. A square-wave is used because the output transistors switch completely on and completely off quickly. When they are switched on, the voltage across them is very low so their power dissipation...
  11. audioguru2

    AC-DC Inverter Circuit Principles

    A 555 uses a pot to adjust its duty-cycle. Pin 5 can change the duty-cycle only a little. Usually a PWM controller IC (TL494 etc) is used because it has all the features needed to make a high frequency PWM pure-sine-wave inverter. Make the mains-frequency sine-wave any way you want.
  12. audioguru2

    Magnavox TV Converter box

    Is your converter box converting the new broadcasted digital channels to analog? Its parts might be specially made for it and not available to you. They will also be extremely tiny.
  13. audioguru2

    AC-DC Inverter Circuit Principles

    A 25kHz ferrite transformer is inexpensive, small and light weight. Your 50Hz iron transformer will be expensive, huge and heavy. The 25kHz circuit produces a pure 50Hz sine-wave. Your 50Hz circuit produces a square-wave or a modified square-wave.
  14. audioguru2

    0-30V Stabilized Power Supply

    It can dissipate 200W if its case is cooled to 25 degrees C somehow (liquid nitrogen spraying on a huge heatsink?). Your math is wrong. The load dissipates 150W not the output transistor. The 30VAC transformer has a peak voltage of 42.4V. The rectifier bridge drops 2V and the main filter...
  15. audioguru2

    Magnavox TV Converter box

    I get my TV converter box from my cable TV and internet provider company. Every two months when the TV box or cable modem fails, I return it and they throw it in the garbage and give me a replacement new one. I like going there to see the pretty young ladies who work there. ;D
  16. audioguru2

    intercomm

    A cheap very old intercom is half-duplex. I press a button to speak and you hear it. But while I am pressing the button it disconnects your microphone so I can't hear you. If you speak then you press your button that disconnects my microphone. So you cannot hear me. Full-duplex allows each...
  17. audioguru2

    0-30V Stabilized Power Supply

    The original circuit has many overloaded parts. The OPA445 will not work in the latest schematic. I don't have the modified schematic for the OPA445 opamps because that was years ago and the schematic is the same as the original except R10 must be connected to -5.6V. Here is the parts list:
  18. audioguru2

    opamp roll-off

    Most datasheets do not have enough frequencies listed. This one is from Philips and it has correct logarithmic frequencies.
  19. audioguru2

    Phase shift Oscillator

    Like I said on the other website, the meter in your sim reads RMS not peak output voltage. Also the old 741 opamp in your sim has a max output that is 1V less than the supply voltage but a real 741 opamp has even more loss. So the max output of the opamp is 11V and the RMS output voltage is 11V...
  20. audioguru2

    0-30V Stabilized Power Supply

    One guy powered a switching power supply from this project. It caused C7 at the output of this project to get hot and explode.
Top