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  1. audioguru2

    0-30V Stabilized Power Supply

    Correct. But a 100V one is much better. Of course the output transistors get very hot and must have a heatsink. Use one very big heatsink for both or use a smaller but still pretty big heatsink for each one. When the output voltage is low or shorted and the current is set to 3A then each 2N3055...
  2. audioguru2

    0-30V Stabilized Power Supply

    A 4A transformer is 95% of what is needed (4.2A) so it can be used. The KBPC10005 has a voltage rating of only 50V which is not enough. Use a KBPC1001 which has a voltage rating of 100V.
  3. audioguru2

    0-30V Stabilized Power Supply

    No. It will overheat. It can supply 30V at 3A which is 90VA. But the rectifier works with the peak voltage that is 42.4V so when the project has an output of 3A then the transformer must supply 42.4V x 3A= 127.2VA. Use a 28V or 30V transformer rated at 4.2A. Build it and adjust it without...
  4. audioguru2

    0-30V Stabilized Power Supply

    You show my latest schematic and parts list. I don't know anything about the pcb design.
  5. audioguru2

    0-30V Stabilized Power Supply

    It is impossible to get +53V when you rectify and filter 30VAC. The peak voltage is 30V x 1.414= +42.4V and the full-wave bridge rectifier drops it to +40.4V. The max output from the project is about +35V when it is loaded then the calibration trimpot drops it to a max output of 30.0V. You do...
  6. audioguru2

    0-30V Stabilized Power Supply

    The fixed and corrected project will not work with TL081 opamps!!!! I selected Motorola (ON Semi or another name today) and Texas Instruments opamps because they do what is required and are available almost everywhere. Their max allowed supply is 44V. The max supply for a TL081 is only 36V so it...
  7. audioguru2

    12V 60W Amplifier

    But many car radio amplifiers produce 60 Whats when the supply is only 12V. 60 Whats is the true power of 1W multiplied by the age of the school kid designer's grandmother. Just a bunch of lies. Many car radios have four channels. Then they produce the true power of 60 Watts (15W per channel...
  8. audioguru2

    0-30V Stabilized Power Supply

    Tesseract's schematic does not show P1 or P2. On my schematic, P1 is the voltage control and P2 is thew current control. If P1 is at max and the voltage trimpot is calibrated then the output voltage is 30V (or less when the current is higher than the current control setting). Since your voltage...
  9. audioguru2

    12V 60W Amplifier

    Two 8 ohm speakers in parallel have a total of 4 ohms so the current is doubled and the power is also doubled. But a 12V supply results in an output swing of only about 8V peak-to-peak which produces a power of only 2W into 4 ohms. For many years, car radios use two amplifiers in a bridge for...
  10. audioguru2

    About the opa445

    The very high stray capacitances of a breadboard connector tracks to each other and to the many connecting wires causes modern high frequency opamps to oscillate at a high frequency which causes them to get hot. A breadboard was fine with a lousy old (43 years old) 741 opamp that has poor high...
  11. audioguru2

    0-30V Stabilized Power Supply

    Since the rectifier bridge peak detects the 30VAC to 42.4VDC then the 3A DC output from the project requires 4.2A AC from the transformer. If your transformer is rated for an output of 3A then it will over-heat if the project has an output of more than 2.1ADC. Its voltage will drop when it is...
  12. audioguru2

    0-30V Stabilized Power Supply

    Since you changed the transistor part number then why didn't you look at its datasheet to see its pins?? The BC556 is European with the normal pins layout for there. The NTE might be American with the normal pins layout for there. Oriental transistors have a different pins layout than both of...
  13. audioguru2

    About the opa445

    The datasheet lists their thermal resistance differences. 2) The second question is, recently, I bought a OPA445AP to design a power amplifier. The power amplifier is chose to be inverting power amplifier. The input resistor and output resistor are 3M Ohm and 12M Ohm, so the gain is 12M/3M=4 if...
  14. audioguru2

    0-30V Stabilized Power Supply

    C5 on the schematic you used is only 220nF (0.22uF) so it is an unpolarized metallized poly film or ceramic. Both types of capacitors do not have a top like is on an electrolytic capacitor. The voltage rating of C5 should be 63V. The max voltage it will ever see is 43V.
  15. audioguru2

    Radio Cassette Corder - Philips DR435 and AKAI AJ W239

    Are you still playing (and recording) cassette tapes?? They were popular here in The West 21 years ago but we stopped playing them about 11 years ago. I worked for Philips when they introduced the cassette tape recorder/player 48 years ago. 
  16. audioguru2

    0-30V Stabilized Power Supply

    No. This project does not use a center-tapped transformer. You need a schematic that shows how the two wires from the secondary of the transformer connect to the bridge rectifier and how three of the wires from the bridge rectifier connect to the circuit. I assume that + is the positive output...
  17. audioguru2

    0-30V Stabilized Power Supply

    Tesseract's schematics are WRONG. The collector of the driver transistor is correctly shown connected to the unregulated positive supply and the collectors of both output transistors also should connect there. The emitter of the driver transistor should connect to both bases of the output...
  18. audioguru2

    0-30V Stabilized Power Supply

    This project uses a max power of 3A x 40V= 120W from the mains. So if your mains is 120V then a 1A fuse might blow so use a 1.5A slow-blow fuse. If your mains is 240V then use a 0.75A slow-blow fuse.
  19. audioguru2

    0-30V Stabilized Power Supply

    When this project is turned on, the very high value filter capacitor C1 takes a very high current to charge in less than 1 second so your fuse blows. Use a slow-blow fuse.
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    In reply #1602 you are looking at PicMaster's schematic and pcb. His "shunt resistor" is R7 on all the other schematics and senses the output current. It is 0.47 ohms for 3A max and is 0.27 ohms for 5A max. It can also be used as the shunt resistor in a current meter.
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