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  1. audioguru2

    Op amp theory Q's

  2. audioguru2

    Key Finder (pinoy version)

  3. audioguru2

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

    Hi Logan, It is normal for the base of the transistor to be about 0.55V to 0.7V when it is turned on. It should be off and measure 0V when pin 15 of the IC is also 0V. If the transistor has the 4.7k resistor in series with it like in my 1st modification of the original circuit, then you can test...
  4. audioguru2

    sustitute for IC KV1310 & IC 2N4427

    Hi Tinu, Welcome to our forum. ;D Maybe you can't find them because they are not ICs. The 2N4427 is a VHF transistor. The 2N3866 is better and is on the same datasheet. They are made by 4 manufacturers. The KV1310 is a dual varactor tuning diode. It is made only by Toko. Philips might have...
  5. audioguru2

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

    We removed the transistor and modified the circuit to make a 4kHz oscillator for a piezo speaker. If you install a new transistor (the one you had is damaged) like in the original project or slightly re-wired like in my 1st modification, and use the original values for R10 and C5 then a piezo...
  6. audioguru2

    Key Finder (pinoy version)

    1/4W 5% carbon-film resistors with values from 10M to 22M have been available "everywhere" for years. Yes. Lower values in series that add up to 10M. Their extra wiring might pickup interference. Use an electrolytic.
  7. audioguru2

    I CAN'T READ THEM

    I'm helping my son pack now then tomorrow I'll help him move, then celebrate. ;D I just took another look at my lab: EEK! It's a bigger mess than I thought. I might get slower and cheaper cable internet so I can continue chatting with all you good guys. ;D
  8. audioguru2

    Hey, I'm young again!

    Happy 60th, Staigen. ;D ;D Welcome to the club of old geezers feeling young again. I kept most of my old vinyl records but I like the new music too.
  9. audioguru2

    I CAN'T READ THEM

    I'm too busy celebrating so I can't take pics. Horray, my son is moving out! ;D He is taking his digital camera with him and his share of the cost of my high-speed cable internet connection.
  10. audioguru2

    urgent

    1) Which type of microphone? Electret? Dynamic? 2) How much power to the speaker? 3) What power supply voltage? 13.8V from a car's battery? All of our circuits "really work". Some of them are "ezy" to make. What went wrong with the circuits you tried? Too much smoke? ;D ;D
  11. audioguru2

    I CAN'T READ THEM

    ;D ;DHee, hee. ;D ;D My lab is a mess. You don't want to look there. I know where everything is located, but I wouldn't be able to tell somebody else where to find some things. "It's under the green circuit board from the answering machine that is forward and to the left side of the ....."
  12. audioguru2

    I CAN'T READ THEM

    Hi Awright, I thought that I am an old geezer and you must be even older than me. ;D I agree that building kits is a good way to learn electronics in addition to studying the facts. My 1st few kits were an audio power amplifier, an FM tuner, an oscilloscope and a transistorized voltmeter. Then...
  13. audioguru2

    Transformer Power Rating

    Yes, but its wire size is small so it might get crushed. I would use 1mm wire for an airwound coil.
  14. audioguru2

    Transformer Power Rating

    I beat you by less than 3 minutes! Great minds think alike. ;D
  15. audioguru2

    sensitive parabolic michrophone

    Hi Shahriar, That project has a terrible translation into English. Its 0.1uF cap and 4.7 ohm resistor begin applying a load to the output of the amp at 340kHz. Crossover distortion occurs at all audio frequencies and is caused by not having enough idle current through the output transistors. I...
  16. audioguru2

    Transformer Power Rating

    Many other amplifiers I've seen have nothing inside their coil at the output. Since your 1W resistor is the correct diameter then it will be fine.
  17. audioguru2

    Key Finder (pinoy version)

    Hi Logan, Why are you changing the values of 8 capacitors, some of them a lot? It won't work with your values of C2, C3 and C4 so low. It won't work with your values of C5 and C9 so high. 
  18. audioguru2

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

    Hi Logan, It is too bad that your time is up before you found out why your circuit didn't work. It probably would have worked if you had a piezo buzzer with a built-in oscillator as spec'd in  its parts list. You should continue talking about the other project in this thread because it has its...
  19. audioguru2

    sensitive parabolic michrophone

    Hi Shahriar, No, the RC at the output doesn't affect crossover distortion that is low in an LM386 anyway. My old databook has many more pages than the datasheets on the web and explains that it has oscillation without the RC.
  20. audioguru2

    Op amp theory Q's

    Hi TG, 1) The value of your input caps C3 and C4 cause a low frequency cutoff (-3dB) at 80 Hz which is bad for music having deep bass, but is OK for speech. 2) R3, R4. R9 and R10 don't do anything except add noise and should be removed. 3) What is P3 for? All it does is to overload IC1. 4) The...
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