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  1. audioguru2

    Window Car circuit

    Are you talking about a power window that is already on a car? Then the cost of all of its parts and wiring are designed for its slow speed. If you want more speed then you need to apply more power to a bigger motor. The bigger motor will need different and stronger gears. The fuse and wiring...
  2. audioguru2

    Beats by Dr. Dre Headphones

    Their website has no details so I think they sell cheap ordinary headphones, take lots of your money then laugh at you. What does the battery do?????
  3. audioguru2

    how to send ECG through gsm

    I don't know why an ECG would be sent on GSM. Maybe the patient is dying and is far from the doctor or hospital. I had a heart attack two years ago and had many ECGs. They fixed the blocked heart arteries but my heart doctor wants to see if my heart is getting better or is getting worse. So he...
  4. audioguru2

    volume control

    A volume control has been a variable resistor for many years. A transistor can mute the sounds but is not a volume control. A transistor can make a sudden change in level (a jerk) when it is in a voltage divider. Many years ago electric guitar people made a volume control with a Jfet...
  5. audioguru2

    Thesis

    You speak in a foreign language half the time so we don't know what you are talking about. We speak only English here, not Filipino. Maybe you should go to the other website called Electronics-Lab but it is in The Philippines.
  6. audioguru2

    0-30V Stabilized Power Supply

    A 31V transformer might produce 32VAC without a load. Then its peak voltage is 45.3V and the bridge rectifier reduces it to 44.1V. Opamps U1 and U2 will operate or will blow up with the 44.1V supply which is higher than their max allowed supply of 44.0V. The voltage will be even higher when the...
  7. audioguru2

    FET Amplifier Biasing

    No. Most Mosfets are enhancement type, but most Jfets are depletion type which is completely different. A Jfet is biased with just a gate resistor to ground and a source resistor to ground. No. Microcontrollers, microprocessors and Cmos logic ICs use Mosfets with a very low supply voltage. A...
  8. audioguru2

    Battery pack from laptops?

    I used two Li-Ion cells from a laptop battery to power my old electric RC airplane. I charged them properly and did not discharge them too low. You could use them to power a toy car. But the Li-Po batteries in my new electric RC airplanes have a much lighter weight and much more power.
  9. audioguru2

    FET Amplifier Biasing

    A Jfet is used when you want a very high input impedance but a Mosfet can also be used. Many opamps have Jfet inputs. sometimes a Jfet was used for an automatic level control circuit like an audio compressor, audio limiter or to stabilize the level of a sine-wave generator.
  10. audioguru2

    FET Amplifier Biasing

    A simple crystal radio has no voltage gain so it needs the very strong signal provided by a long antenna, a ground and a strong local station. But a real radio has a very high voltage gain so it simply amplifies the tiny signal it receives. It has AGC so it attenuates its gain when it receives a...
  11. audioguru2

    Is it a hartely oscillator??

    No. I explained how the center-tapped inductor inverts the signal with 180 degrees phase shift so the transistor provides the other 180 degrees phase shift for it to oscillate.
  12. audioguru2

    0-30V Stabilized Power Supply

    A pot used for "fine" adjustment is always in the wrong position and might be forgotten. Simply use a very big knob on one pot then it can be turned a lot or turned a little.
  13. audioguru2

    I need power supply of 0-30 volts, 0-3 amps corrected PCB

    Haven't you seen our discussions about its problems and fixes for them in the forum? There are a few pcb designs for the fixed version.
  14. audioguru2

    Is it a hartely oscillator??

    A simple calculation shows that the 1000pf of C1 has a reactance of only 5.9 ohms at 27MHz so it is almost a dead short with no phase shift. The center-tapped coil has 45 turns on the collector side and the same 45 turns on the base side so the base signal is the same amplitude as the collector...
  15. audioguru2

    Is it a hartely oscillator??

    A center-tapped single inductor is used because it inverts the signal. The collector of the oscillator transistor produces a signal at one end and the base receives the signal at the other end. The signal is inverted to produce positive feedback to sustain oscillation. The transistor can have a...
  16. audioguru2

    0-30V Stabilized Power Supply

    Goodie! I am glad you fixed it.
  17. audioguru2

    0-30V Stabilized Power Supply

    Then the 2N3055 transistor that was connected to +35V does not work.
  18. audioguru2

    0-30V Stabilized Power Supply

    The BD139 will take the entire load if the base and emitter of one 2N3055 is shorted together or if both 2N3055 transistors do not have their collectors (their metal cases) connected to +35V.
  19. audioguru2

    0-30V Stabilized Power Supply

    Hi Lighty, If the shorted output current is only 1.7A then each 2N3055 transistor has 0.85A. Their minimum current gain is 54 at such a low current so their base current which is also the collector or emitter current of the BD139 is only 1.7A/54= 31.5mA. The BD139 has 34V across it so it...
  20. audioguru2

    0-30V Stabilized Power Supply

    The output now is only 0.22V so simply live with it. Maybe the 2.0V was caused by leakage in the 2N3055 transistors or in D19. Somebody else tried a 10uF film capacitor for C7 which fixed his problem with the output voltage not going down to 0V.
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