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  1. audioguru2

    Gmrs radio please help

    Go to www.google.com and in the search box enter GMRS Improvements. The 1st link has antennas to improve range and there are many other links in Google.
  2. audioguru2

    Gmrs radio please help

    Isn't your GMRS radio just a little portable high-power multi-channel walkie-talkie with a built-in antenna? I've never seen an additional antenna for one. My FRS radios work perfectly with their built-in little antennas.
  3. audioguru2

    Gmrs radio please help

    Your GMRS radio must be defective if it picks-up a radio station. Maybe the station is very close and is overloading your radio.
  4. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tedy, Your Zener dagram is confusing. It shows the polarity of ordinary diodes, not zener diodes. Your D7 is installed correctly. D5 also has its cathode to ground. Your lowest voltage is at C3, maybe it is shorted. Do you have a 4-diode full-wave-bridge rectifier for D1 to D4? Is the...
  5. audioguru2

    UCN 4401A

    It is old, this is just its brief spec's: http://www.datasheetarchive.com/semiconductors/specsheet.php?specsheet=2187023
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Isn't D7 installed backwards?
  7. audioguru2

    High Quality electronic sites

    Google gives my IE6 all the Silicon Chip projects that I know the names of. Their Micromitter and Scoreboard and all kinds of good stuff are now on my hard drive for free. They have too many ads.
  8. audioguru2

    0-30 Vdc Stabilized Power Supply

    Did the circuit make about -5.6V? If it was much less then Q1 will turn on when it shouldn't.
  9. audioguru2

    help about this supply

    Hi Guys, I simulated the circuit of the "variable voltage regulator" and it oscillated unless the output capacitor was removed. Its voltage regulation was 50 times worse than an LM317 or LM350 which is much simpler and costs less.
  10. audioguru2

    Transformer Power Rating

    The project doesn't say its value so you could calculate it, then buy one and wire it in parallel with its resistor. The poor translation messes-up its simple construcion instructions. Look at the difference in their voltage ratings, and what happened in the other guy's amplifier that tried it.
  11. audioguru2

    frequency and voltage in DC motor

    Usually when you use old parts, you get lousy old performance. Some of the new PWM IC's use a 1MHz switching frequency, so that tiny or integrated-on-chip capacitors and an inductor can be used. Some young people can hear 20kHz. I heard "ultrasonic burglar detectors" very loudly when I was...
  12. audioguru2

    capcitive touch sensor

    Its shown on the schematic and in the parts list. I've never seen a 470pF cap rated at 630V. Most are only 50V to 100V and would breakdown and maybe short with the mains voltage. If it shorts then the project is deadly!
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes, but R2 and C2 feed the negative -5.6V supply circuit. Q1 is designed to short the output of U2 to ground at the moment that the power to the project is turned off, to prevent the output voltage from rising. The negative supply has a small filter cap that discharges much quicker than the...
  14. audioguru2

    key chain laser power supply

    Hi Steven, 1) What is the voltage across the laser diode in operation? 2) What is its current? You can calculate its current by measuring the voltage across the 10 ohm resistor. 3) What is the dropout voltage of the 7805 regulator? Its output voltage will no longer be regulated when the battery...
  15. audioguru2

    led problem

    No, The 330 ohm resistors set the current at max for max brightness when the switch bypasses the dimming resistor. I don't know how dim you want it to be. 3.3k ohms would be pretty dim. Stick a pot in there and adjust it to the dimness you want, measure its resistance and wire-in a resistor of...
  16. audioguru2

    LED amperage question

    The forward voltage drop of most red LEDs is a little less that 2V at their absolute max continuous current of 30mA. They are a diode and without a current-limiting resistor the current is infinite!
  17. audioguru2

    Need help in using Darlington Pair IC ULN2003A

    Hi Ashtead, I couldn't find a datasheet for an old ULN2003, but the new ULN2003A has pin 9 different from your description.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Tedy, U2 would get hot if Q1 is conducting when it shouldn't, maybe because the negative -5.6V supply doesn't work. Maybe the spark came from something in the negative supply.
  19. audioguru2

    500W_inveter

    Hi Sure, Welcome to our forum. ;D The oscillator in a CD4047 is pretty simple and is guaranteed to work with a supply voltage of 3V to 18V or more (22V for TI). Since yours stopped then later blew-up, I think it was bad from the start. I agree that adding a 100 ohm resistor to feed its power is...
  20. audioguru2

    capcitive touch sensor

    Dangerous! What low value capacitor and what is its high voltage rating did you connect the live mains to the project's circuit ground?
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