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  1. audioguru2

    Thesis

    When I was a manager on a car radio production line I interviewed some graduate electrical engineers who knew nothing about electronics.
  2. audioguru2

    PWM Without PWM IC

    Your circuit is completely wrong. Its output voltage will change when the temperature changes. Every voltage regulator uses a reference voltage that does not change. But your "voltage regulator" uses the base-emitter voltage of a transistor that changes when the temperature changes. It also...
  3. audioguru2

    0-30V Stabilized Power Supply

    When I added the 10V zener diode to reduce the supply voltage to Q3 and U3 I added the 100nF capacitor because all opamps need a supply bypass capacitor. But I forgot to number it. The oroginal schematic used R15 but it was useless. Delete it. The 10V zener diode is important. The 5.6V zener...
  4. audioguru2

    0-30V Stabilized Power Supply

    An 18V transformer produces a rectified and filtered full current voltage of 23.4V but with a couple of volts of ripple so the troughs of the ripple are at 22.4VDC. The output transistors, their emitter resistors, the driver transistor Q2, the opamp U2, the bridge rectifier and the current...
  5. audioguru2

    Making switching NPN with PNP

    Your new circuit is missing a resistor between the collector of the A733 PNP transistor and the base of the TIP142 darlington transistor. The 4.7k resistor is noy much of a load for the very powerful darlington transistor. Unless we know the load current then we cannot recommend the value of the...
  6. audioguru2

    0-30V Stabilized Power Supply

    Heating in the output transistors, the driver transistor Q2, bridge rectifier and R7 is caused by the voltage across them times the current through them. If there is no load current then there is no heating in these devices. The most heating is produced when the current is the highest (3A) and...
  7. audioguru2

    0-30V Stabilized Power Supply

    R3 gets warm so it should be 1/2W or 1W. The schematic and parts list should call the LED D12 and the 10V zener diode D13.
  8. audioguru2

    0-30V Stabilized Power Supply

    For a max output current of 2.3A then C1 can be reduced to 2.3/3 x 12000uF= 9200uF which is not a standard value. Use 10000uF. I haven't seen a 1/2W resistor for about 45 years.  If yours are that old then they probably have their values changed.
  9. audioguru2

    HELP! current booster.

    I don't believe that students know nothing about electricity nor about energy. I guess their teacher is hopeless.
  10. audioguru2

    0-30V Stabilized Power Supply

    The original circuit uses many old and parts too small that overheat then the circuit does not make 30VDC at 3A. The improved circuit will probably work well with a little 24V/3.3A transformer then its max output might be 24VDC at 2.3A. You should adjust the calibration so that when the voltage...
  11. audioguru2

    can you help me?

    The old AC adapter will say on its label if its output is AC or DC, its output voltage and its max output current. It should say if the output voltage is regulated. It might show a picture of its connector and its polarity. Simply buy an AC adapter that has the same output voltage (AC, DC and...
  12. audioguru2

    noise cancelling circuit

    The project I posted has a volume control for the mic so it can be adjusted for almost perfect cancellation of the noise that leaks through the headphones.
  13. audioguru2

    noise cancelling circuit

    The headphones "leak" noise from the outside. The mic picks up the noise (not the signal), the circuit inverts it then adds it to the headphones input so it cancels the noise.
  14. audioguru2

    noise cancelling circuit

    In the link I posted, the mic is shown outside the headphones.
  15. audioguru2

    0-30V Stabilized Power Supply

    Hi Nem, I am glad to see that you found the problem in the pcb wiring. But the traces on the pcb seem to be much too narrow for the very high charging current of C1 that might have 15A peaks.
  16. audioguru2

    How to distinguish between FM and AM transmitter circuits

    The sim program did not read the details of the datasheet of the transistor so it doesn't know that the capacitance of the transistor changes when its voltage changes. But your frequency is so low that the very small change of the capacitance of the transistor causes a very small change in the...
  17. audioguru2

    Help about op-amp...

    The opamps you are looking at are 40 and 42 years old. There are much better ones available today for nearly the same cost. The Japanese 741 opamp datasheet does not say the supply current like American datasheets do but shows a graph of the power dissipation vs supply voltage on page 10. For...
  18. audioguru2

    FM Transmitter help!

    Sorry. Since you don't know anything about electronics then it might take me a few months to teach you what each part does in the extremely simple circuit. Maybe you can find a tutorial in Google. Basically R3, Q2, L1, C5, C6, the battery voltage and the distance of anything to the antenna set...
  19. audioguru2

    0-30V Stabilized Power Supply

    Ripple on a power supply is in triangular waves with a quick charge then a slower discharge. Yours has square-waves maybe from an overloaded transformer or from transformer current in the amplifier circuit or from pickup if the transformer or rectifier is near a sensitive amplifier part. With...
  20. audioguru2

    Is it a hartely oscillator??

    It might be used in a very simple and cheap child's toy for remotely turning something on and off when it has a simple receiver.
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