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  1. audioguru2

    Problems lately accessing this site

    This site is intermittent. Just try again and it works. Maybe the server has some bad inputs.
  2. audioguru2

    i need help extending the keys finder project. can someone help me out????

    My daughter bought a Chinese-made keysfinder. It kept beeping whenever she spoke softly or if the TV was playing. These kind of circuits are awfully too simple to do a proper job. I think it hears its own beep which makes it continue. Short the mic and it should stop beeping.
  3. audioguru2

    i need help extending the keys finder project. can someone help me out????

    Good, the IC and transistor are working. It is supposed to make about 8 beeps per second. Much too low. What resistor value do you have to connect it to 3V?
  4. audioguru2

    Problems lately accessing this site

    Now the REPLY button is instant. The site is very intermittant.
  5. audioguru2

    Problems lately accessing this site

    Staigen, the QUOTE button works fine. Accessing the site is nice and quick now. But the REPLY button takes forever to do anything and frequently gives the "Cannot find Sever" problem as before. My ISP said the Server in New Orleans is down. The company in New Orleans said the server isn't...
  6. audioguru2

    Op amp theory Q's

    Hi TG, A sim doesn't show the 0.00008% distortion that you hear (?) with a non-inverting opamp. It also doesn't show the 0.000008% distortion that you can't hear with an inverting opamp. Maybe the difference that you hear is caused by the inverting opamp circuit cutting-off the bass? Maybe you...
  7. audioguru2

    Some kind of RPM counter

    Sorry, but your LM2917 circuit won't work: 1) The LM2917 has a 7V zener diode at its supply pin that will blow-up when you apply 15V to it. 2) The 8-pins versions have a differential amp at their inputs with one input grounded and have hysteresis, so their input voltage must swing above and...
  8. audioguru2

    Problems lately accessing this site

    Hey! The site is working again! I thought it was out of business so I was e-mailing most people I know to continue their projects. ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D ;D    ;D ;D...
  9. audioguru2

    Universal Laborator System!

    I worked with large intercom systems (hundreds of loudspeaking stations) for many years. The best ones used PAM which is Time-division Amplitude Multiplexing. Internally inside the exchange, a single wire carried the voices or background music of 20 sources. The wire was multiplexed at a very...
  10. audioguru2

    Transformer Power Rating

    Datasheetarchive.com found a difference: The ability to dissipate heat. Only 3 companies make the BDW83D and BDW84D. Many companies make the C version. A "no name brand" company makes the D with a 150W rating but ST Micro who make only the C version have a rating of only (!) 130W. I also...
  11. audioguru2

    report trouble.......

    Hi Zeus, Welcome to our forum. ;D Did you make a kit? Can you attach its schematic or provide a link to its schematic and parts list?
  12. audioguru2

    i need help extending the keys finder project. can someone help me out????

    It is obvious that when you short the transistor's base to ground to shut it off and it doesn't shut off, then it is bad or it is wired wrong.
  13. audioguru2

    Key Finder (pinoy version)

    I always look at the datasheet for the caps I use then always use the same brand. I don't know who made your caps but the "green caps" I have from the Orient are marked 152 for 1.5nF which is 0.0015uF, and 223 for 22nF which is 0.022uF. My European polyester caps replace the decimal point with...
  14. audioguru2

    Key Finder (pinoy version)

    I have two from alarm clocks that work fine. I looked at RadioShack (now called The Source) yesterday and they had only piezo buzzers, no speakers. I can order online, any piezo speaker that is made. They are piezo speakers. I think they are too small to make a beep that is loud enough.
  15. audioguru2

    i need help extending the keys finder project. can someone help me out????

  16. audioguru2

    Key Finder (pinoy version)

  17. audioguru2

    Power Supply.

    When I glanced at the schematic I saw the 50V rectifier rating and thought it was half the transformer's rating. If it rectified the 50VAC to get 68VDC then at 65A the poor output transistors will melt with 3.5kW!
  18. audioguru2

    need help on noise protection

    You need 3 opamps to make a true differential amp.
  19. audioguru2

    Power Supply.

    Since the circuit uses TIP26 transistors that don't exist and has its LED upside down I think it is a joke.
  20. audioguru2

    need help on noise protection

    Hi Black Wing, An amplifier for ECG pickup uses an Instumentational Opamp specially designed with true differential inputs and the gain setting resistors with extreme accuracy built-in to avoid hum pickup. Your circuit has a low 10k input impedance to high frequecies and is -3dB down at 160Hz on...
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