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  1. audioguru2

    0-30V Stabilized Power Supply

    It is difficult to test a current regulator with a motor because the current draw by the motor changes with its mechanical load. Its current is higher when it works harder and when it starts. The current regulation reduces the output voltage until the output current is the amount of the...
  2. audioguru2

    what the hell is this circuit? weird opamps

    The opamps have a single-polarity supply so they are biased at half the supply voltage with R3, R4 and R10. R2 is usually not needed. Since the opamps are DC-coupled then only the first opamp is biased and it biases the second opamp. The first opamp is a follower that has a very low output...
  3. audioguru2

    FM Transmitter Help

    Hi Nguroje, Your stripboard layout is similar to mine but is missing the very important 1000pF high frequency supply bypass capacitors. The electrolytic bypass capacitors are good for audio frequencies but are useless at 100MHz.
  4. audioguru2

    0-30V Stabilized Power Supply

    C7 will blow up if its polarity is backwards or if the bridge rectifier is defective or connected wrong and applies AC to the circuit instead of DC. Another person had his C7 blow up when his power supply project was powering a switching power supply circuit. If the project has a load and is...
  5. audioguru2

    0-30V Stabilized Power Supply

    I said to null the input offset voltage of the opamp in the current regulator circuit exactly the same as it is done with the opamp that is in the output voltage amplifier. With a trimpot and resistor between pin 1 and pin 5 of the opamp. Again we are sorry that PicMaster changed all the parts...
  6. audioguru2

    0-30V Stabilized Power Supply

    The peak voltage is 30V x 1.414= 42.4V and the bridge rectifier reduces it to 41.0V with no load. Maybe your filter capacitor was charged to a higher voltage. R1 should slowly discharge it.
  7. audioguru2

    0-30V Stabilized Power Supply

    If the output is shorted then the current regulator limits the current to its setting. all the parts should be rated and cooled so they do not get too hot. the fuse should be in series with the high voltage power on/off switch. Use a slow-blow fuse rated for a draw of 150W. Your opamp U3 has a...
  8. audioguru2

    0-30V Stabilized Power Supply

    Good! I am glad you fixed it. :)
  9. audioguru2

    0-30V Stabilized Power Supply

    Hi Fikic, Your schematic is correct. Your pcb is an Eagle file that I cannot open because I do not use Eagle. Check the values of R2, R3, C2 and C3. Replace diodes D5 and D6.
  10. audioguru2

    Need help in 4th-Order Source Follower Lowpass Filter design

    I have always used Sallen and Key for lowpass and highpass filters.
  11. audioguru2

    0-30V Stabilized Power Supply

    The LED is supposed to turn on when the current regulation is beginning to reduce the output voltage. If it is calibrated to begin current regulation when the output current is 3.0A then its should begin current regulation at less output current when the current adjustment pot is turned down...
  12. audioguru2

    0-30V Stabilized Power Supply

    Hi Fikic, In order for the current regulator to limit the current when the output is shorted then the anode of D9 must go very close to ground which causes the output voltage to be very close to ground which limits the current. Then the output of U3 must go down to about -0.7V. A TLE2141 or...
  13. audioguru2

    FM Transmitter Help

    I have two pcb designs made by people for my Mod4 FM transmitter. I haven't tried them and nobody said they work. Here is the most detailed one: FM_Tx__mod4._Bottom.pdf FM_Tx__mod4._SS_Top.pdf
  14. audioguru2

    0-30V Stabilized Power Supply

    To make a negative power supply you make the project and use the + output as ground and use the GND output as the negative output. Its transformer must be completely separate from the positive supply project transformer but they can use a single transformer with two completely separate windings.
  15. audioguru2

    0-30V Stabilized Power Supply

    The trimpot beween pin 1 and pin 5 of U2 nulls its input offset voltage. With the voltage set to 0V then the trimpot is adjusted for ezactly 0.0V. With the output voltage set to maximum then the voltage calibration trimpot is set to 30.0V. With a 3A load and the current regulation set to...
  16. audioguru2

    0-30V Stabilized Power Supply

    I hate the confusion caused when somebody takes an existing circuit then changes all the parts designation numbers. I don't know which one is correct and don't have time to sort it out. Ask Picmaster.
  17. audioguru2

    FM Transmitter Help

    It won't work if you build it on a breadboard or with its parts spread too far apart. It must be made on a compact pcb or stripboard layout like I did. C5 allows Q2 to be a common-base amplifier so it can oscillate. Without C5 then Q3 will get hot without having a signal. But adding C5 to your...
  18. audioguru2

    0-30V Stabilized Power Supply

    A few people like Redwire and Picmaster have designed a pcb for this version of the project. They are somewhere in this or in the other thread.
  19. audioguru2

    0-30V Stabilized Power Supply

    Mounting kits are sold for TO-3 or for TO-220. Mica insulators are also sold for both. Depending how you will mount the heatsinks, the transistors can be bolted directly to the heatsink then the entire heatsink can be insulated from touching ground, or the transistors can be insulated from the...
  20. audioguru2

    0-30V Stabilized Power Supply

    The circuit will work with a 22VAC transformer but its max output will be about +28V with no load and about +23V with a 3A load. When you turn the voltage setting pot higher then the output will be full of ripple when there is a load.
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