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  1. audioguru2

    4W FM Transmitter

    Sasi, that's a cool transmitter you have.
  2. audioguru2

    Piggy-backed PC power supplies?

    The power supplies are already filtered and get their feedback directly from their outputs. Therefore you must isolate them from each other, maybe with just a 0.1 ohm resistor in series with the output of each one. If each one is supplying 10A, the power dissipation of its 0.1 ohm isolating...
  3. audioguru2

    opamp biasing class A

    Hey, where's my pic? It must have gotten stuck on the old server. Here it is again. Look at the extremely low distortion of the opamp, parts per million! Those extremists are adding output bias current to it to reduce that distortion. Anyway, opamps have such a high gain that most of it is...
  4. audioguru2

    Need help with a TV transmitter project.

    Hi Dazza, It looks like Australia's TV channels 3, 4 and 5 are in the FM broadcast band. That's dumb!  ??? Don't the picture carriers make a big noise from an analog-tuned FM radio that tune through them? BUZZZZ! The Poptronix project should give details about the sound IF transformer, its mfr...
  5. audioguru2

    Designing feedback amplifier

    Hi Yousef, I have added DC operating voltages to my opamp sketch that shows that all opamps can swing their outputs about 10V peak-to-peak or more with an AC signal. If you don't understand how single supply opamps that are AC coupled can operate exactly the same as dual supply opamps that are...
  6. audioguru2

    Need help with a TV transmitter project.

    Hi Dazza, Your TVs have a sound IF of 5.5MHz. The transformers look to be the same except for their numbers. You might need a service manual to find the right one. Nothing else needs to be changed but what about channel frequencies? Does the article say anything about RF frequency?
  7. audioguru2

    Additional Information

    Hi Nab, The voltage gain of IC1A is exactly 101. It is not adjustable so there is no minimum or maximum. The signal gain in decibels is slightly more than 40dB.
  8. audioguru2

    Very basic question from a newb

    Hi Adverse, The problem with using a resistor to reduce the voltage to the fan is that the voltage changes backwards to what it needs. It the fan slows down for some reason, it draws more current which causes more of the supply's voltage to be across the resistor, not the fan. Hence, even lower...
  9. audioguru2

    Need help with a TV transmitter project.

    G'day Mate, Its picture would be upside down, wouldn't it? You would need to drink many Guinness to turn it around!  ;D ;D The Poptronix project is meant for North America, I don't have a clue about Australia's channel frequencies or whether your TV stations' sound carrier is 4.5MHz from the...
  10. audioguru2

    AM to FM convertor

    Hi Alun, What do you think will be the output of an FM radio that tunes-in this thing? http://www.electronics-lab.com/projects/rf/026/index.html If the AM band is crowded, do you agree with me that it will be a jumble of 15 AM stations, plus mains mains hum and buzz, all mixed together?
  11. audioguru2

    4W FM Transmitter

    Hi Dazza, No headache, just fun.  ;D
  12. audioguru2

    AM to FM convertor

    Hi Andbor, I think the coil doesn't have enough turns and the value of the 22pF cap is too high, but maybe they balance each other. If the circuit needs 5pF from the trimcap to tune to 100MHz, what frequency would it tune if you add 50pF track-to-track capacitance of a breadboard? The 22pF cap...
  13. audioguru2

    4W FM Transmitter

    Hi Alun, We use these crappy circuits for entertainment. He, he. We also have a DC motor speed controller that is nothing but a variable frequency oscillator, and a 12VDC to 120VAC inverter that doesn't work and it blows-up its capacitors! Lots of fun. We can't delete them because people have...
  14. audioguru2

    4W FM Transmitter

    Hi Sasi, The author says to keep Q2 in a refrigerator, and doesn't have a pic showing his huge high-velocity fan. He says it draws 400mA at 16V which is only 6.4W. I searched two heatsink manufacturers but they don't have heatsinks for that old 2N2219 anymore. Maybe you can steal a clip-on...
  15. audioguru2

    3V LED Chaser project

    Hi Daemon, Welcome to our forum. I bought my 1nF/63V metalized poly capacitors online at www.digikey.com , their part number 495-1091ND. They are rectangular about 0.25" wide, 0.2" high and 0.07" thick. Their leads are spaced 0.2". I got my 330nF/63V and 470nF/63V capacitors there too and they...
  16. audioguru2

    biasing A Transister

    Hi Allah, You have listed the limits for the transistor beyond which damage will occur. But you did not list its range of current gain, which determines how it operates. The transistor's base resistor must pass enough base current so that the transistor's current gain makes it conduct enough to...
  17. audioguru2

    Please recommend . . . .

    Hi Islw, Welcome to our forum. Boost-buck voltage regulator circuits are available that the LED flashlight makers use. Their circuits are very small because they don't have the massive current of your incandescent lightbulb.The lighbulb wastes about 90% of its input power as heat instead of...
  18. audioguru2

    How to TEST this beast?

    Hi Prateek, If the ohmmeter has a 1.5V battery and the transistor's base requires 0.5V to conduct a bit as shown, then the top resistor will have a current of 45.4uA and the base will have a current of 27.4uA. With its shown current gain of only about 20 at this low current, its collector...
  19. audioguru2

    fm tranismiter

    Hi Alun, Happy Birthday soon! You are not very old like me so why are you selecting old parts? The LF351 hasn't been manufactured for about 7 years by National its inventor, but some shops might still have one. Its noise is lower than a 741 but not nearly as low as a TL071. Just rip apart an...
  20. audioguru2

    How to TEST this beast?

    Hi Rhonn, Does your multimeter have a "diode test" function where it measures the DC voltage across its probes when it supplies a low regulated current from a few volts? Or just an ordinary ohmmeter with at least a 1.5V voltage? Then you can measure if the transistor works, something like what...
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