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  1. audioguru2

    help with LCD power

    Correction: This regulator works much better with 3V more input than the output, like most other regulators, especially ones with higher output current. Its typical Input Voltage Regulation spec is 3 times better, and its Ripple Rejection is not even spec'd with only a 2V difference. It is not a...
  2. audioguru2

    TELEPHONE blaster

    Hi Ante, Yeah, I won big-time over my telco. A bunch of us oldies got together in a class-action law-suit, and proved in court that touch-tone actually saves the telco from having to install more "dialing registers" saving them money, because a register is used quickly and is available sooner...
  3. audioguru2

    TELEPHONE blaster

    Hi Thunder, U R welcome. In my era (about 40 years ago) I made many free long-distance pay-phone calls by grounding the transmitter (microphone) for a moment with a paper-clip! After a few years when the telco saw what was happening, they changed the wiring in a hurry. ;D My home is one of the...
  4. audioguru2

    Electronic Stethoscope 2

    Hi Doctor Emad, 1) Your circuit with two TL071's operates the same as my new project with its TL072. 2) No, I haven't built it, I just wanted to help the many people that complained about the original faulty circuit here, and on the original author's website. I tried an electret microphone...
  5. audioguru2

    help with LCD power

    Hi Bob, Good, you've almost fixed it. I'm glad to have helped. It is still much hotter than expected, dissipating more than 3.5W, so it must have a load of more than 510mA. Your 126 degrees C measurement is on its external heatsink so the actual temperature of its internal chip is much higher...
  6. audioguru2

    help with LCD power

    Hi Bob, Your calculation for power dissipation of the regulator is incorrect. If it is supplied with 12V and is passing 250mA, the source is loaded with 3W (the regulator plus the LCD dissipations). The regulator's pass transistor has only 7V (12-5=7) across it and 250mA through it which is only...
  7. audioguru2

    part replacement

    Noisy, distorted old opamps are crap!
  8. audioguru2

    Electronic Stethoscope 2

    Hi Doctor Emad, My new detailed "Electronic Stethoscope-2" project is here: http://www.electronics-lab.com/projects/science/019/index.html Please start a new topic about it. I have decided that 470uF is good for C8, but 100uF will be fine. The LM386 is powered from only one battery, so that one...
  9. audioguru2

    5 Watt Audio Amplifier

    Hi Clemson, Your 12V supply requirement certainly makes a big difference to the design of your amplifier. As I said earlier, to get 5W into 8 ohms, you need nearly 18V p-p, which is not normally available from a 12V supply. Therefore you need two amplifiers, connected in a "bridge"...
  10. audioguru2

    555 timer help

    Hi Stuee, Never mind the Instant Messaging, let's let everyone see how easy it is to make a long duration timer with the CD4541. Here is a 5 minute timer where the output goes low after the time period (it can be made to go high if you want). Change the cap for a different time period. Add an RC...
  11. audioguru2

    dividers and their duty cycle

    Who is stuttering? See, I can delete posts too!
  12. audioguru2

    TELEPHONE blaster

    Hi Thunder, You've been watching too many cartoons. In the olden days, a switchboard operator connected your phone directly to the other guy's wires. You probably could have sent a few thousand volts to him and fry him and his phone. I don't know when the telco added lightning arrestors to the...
  13. audioguru2

    ERRORS

    Hurray, it works! Hi Mixos, Thanks for fixing the PHP bug. The errors are gone and I notice that the "new button" is also gone. Were they related?
  14. audioguru2

    part replacement

    MP, I don't think that Black Wing wants to play "telephone answering machine mini-tapes" through his new audio mixer project. He probably wants to hear CDs clearly. Good opamps that are designed for audio are available and are not expensive so why not use them today? A local audio equipment...
  15. audioguru2

    5 Watt Audio Amplifier

    Hi MP, Clemson needs 5W into 8 ohms. I was stating that the "car radio" amps that were recommended by others can't do that, and I don't think that he wants to bridge them.
  16. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Bohda, A TL431 is much better than a zener diode with an ordinary resistor. Since D8 is operating inside the constant current feedback loop of U1 in our project, this combination is approximately equal to the performance of a TL431, when the zener and resistor are the parts as discussed...
  17. audioguru2

    ECG for home use

    Kevin, What is not wanted in an ECG is hum pickup and its harmonics from nearby mains wiring. The patient's body acts like a high impedance antenna and the wanted signal is only microvolts. A very high gain is required to make the signal useable. This high gain also amplifies hum. Hum is reduced...
  18. audioguru2

    dividers and their duty cycle

    Hi Shekhar, Simply double the clock frequency of the counter then divide its 3/5 output by 2.
  19. audioguru2

    ERRORS

    Hey, after only a few tries with errors, I am able to reply! Hi Ante, When I see the little red hour-glass beside "Web site found, waiting for reply", I know that it is going to screw-up. I haven't tried the new button much, I am too busy trying to navigate around this site with all those...
  20. audioguru2

    ERRORS

    It is worse today and in the past few days than it has ever been before. I can't get anywhere including to the home page!
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