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  1. audioguru2

    Electronic Eavesdropping Devices Detector

    Hi Erik, Welcome to our forum. Are you guys in the UK charged a fee to turn-on or just to own a TV? That's outrageous! What's the fee for, don't you guys have commercials? Or is it just to pay for their "sophisticated TV detection equipment"? Sounds like a make-work project for the unemployed...
  2. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, Sure you can use a 47K volume control. If it's linear instead of audio-taper, connect a 22K resistor between pin 3 of U5 and ground. You might have to use a shielded cable for its output to U5, because its higher resistance might pickup hum in the wire. You have 3 problems: 1) Your...
  3. audioguru2

    wireless transmitter

    Hi Ras, The Micromitter is designed for Australia's 10mW RF power limit and uses their and Europe's 50us pre-emphasis standard. Check to see what your country's standards are. Here in North America both are different (100mW and 75us). I don't want to discuss politics and I don't know your...
  4. audioguru2

    wireless transmitter

    C'mon up here! Our market has everything.
  5. audioguru2

    Measuring 10mV analogue signal

    What frequency range? What has to be accurate? Voltage level? Low distortion? Low noise?
  6. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, I hope you find an electret mic that works. The noise you call :"shshshshshhhhhhhh", we call "hiss". If you replaced your defective volume control and turn it to zero, if you still hear hiss then it is coming from the LM386. They are cheap but not too bad. Many people use them for...
  7. audioguru2

    Switching power supply

    Hi RP, Welcome to our forum. The data for the 2SC4977 recommends 50KHz switching. Its Tr=1us, Tstor=2.5uS and Tf= 1us. Their total time is 4.5us, which is much longer than 1/2 cycle of 150KHz. No wonder it heats, it is ramping instead of switching. What is your load current? What is the value of...
  8. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, Your microphone is not working properly in this circuit. Maybe it is dynamic type (coil and magnet) instead of electret (condenser with built-in high voltage charge, and FET impedance converter). Get an electronic part electret microphone or take one from a tape recorder, telephone...
  9. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, 1) WHEN YOU SPEAK, he, he, please don't shout, I mean, when you speak into the microphone at a normal voice level and the microphone is about 1/2m from your mouth, with the volume control at maximum can you hear your voice loud and clear in the earphone? If it is distorted turn the...
  10. audioguru2

    Pb-free soldering

    Hi Alun, Battery companies like Eveready don't make Ni-Cad's anymore. They have similar and with much more capacity Ni-MH ones now.
  11. audioguru2

    again, microphone input high school project

    Hi Zgnoh, It will look good connected as "bar mode". I'm glad to help you. 1) I think the word "rectifier" should be changed to "half-wave peak detector", which is the transistor, diode, associated resistors and capacitor. 2) The triangle is the preamp circuit. It is an opamp with a gain of a...
  12. audioguru2

    again, microphone input high school project

    Hi Zgnoh, Oops, page 22 says that the LM3915 was discontinued in 1999, I just checked and the LM3914 is available and works the same but with a linear, reduced range. You must watch your english when talking about inputs and outputs. The microphone's input is your voice, certainly not its...
  13. audioguru2

    Very basic question from a newb

    Hey, aren't we talking about cheap Chinese fans with only sleeve bearings (no ball-bearings)? How long do they last with continuous running at full speed? 1 week, 1 month?
  14. audioguru2

    Pb-free soldering

    Yeah, soon you won't be able to buy it anymore, then the police will be raiding technicians homes, so hide your good PB solder!
  15. audioguru2

    Very basic question from a newb

    I wouldn't use it. Its description mentions pulses, probably to vibrate the train's motor to start it turning at slow speed. It probably doesn't have a filter after rectification so its DC is also AC. Its rheostat for speed control might get bumped and make the fans burn-out, or the rheostat...
  16. audioguru2

    Very basic question from a newb

    A brand new 9V alkaline battery should measure 9.6V and the meter will be on the same range as 12V for the fans.
  17. audioguru2

    Variable digital resistor???????

    Ah, ha. A nice clean Grand Prix GTP. I nearly got one. Many guys change the pulley on the supercharger. Is that a speeding ticket in its windshield? ;D I thought you might have a vintage Fiero. They were also nice but you needed to carry a fire-extinguisher on your back! Instead of tricking...
  18. audioguru2

    Very basic question from a newb

    Hi Adverse, A model train transformer usually doesn't have a filter capacitor that ordinary adapters have. Everything that you measure with your meter measures too high. Maybe your meter is broken and you cannot depend on it. Since you can't measure its output voltage properly, don't use the...
  19. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, Your circuit doesn't work so let's start from the beginning. 1) The microphone must be an electret type. They are used in tape recorders, telephones and cell phones. It should have only 2 pins or connections. One pin connects to its metal case and should be connected to the shield...
  20. audioguru2

    again, microphone input high school project

    Hi Kevin, Thanks for admitting your error. If your triangle wave and sine wave have exactly the same frequency and peak-to-peak voltage, the difference in rectified DC voltage is probably due to the different amount of time that the different waves spend at the peak. The triangle wave spends...
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