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  1. KrisBlueNZ

    Mysterious diode identification help!

    Sounds like the mains switch has failed short. There's no way that you should be able to hear a buzzing from the board if the mains supply to it is switched off. The board will not oscillate with the transducer disconnected. If you run it in this state, the transistors may get hot; I'm not...
  2. KrisBlueNZ

    Mysterious diode identification help!

    Just make sure it's rotated correctly. Measure resistance across the mains input pins; you should measure open circuit. If you measure short circuit, you need to rotate the choke 90 degrees. Good luck!
  3. KrisBlueNZ

    Confusing waveform driving PC speaker.

    C1 and the resistance of the speaker are acting as a "C-R differentiator" This circuit is described at http://en.wikipedia.org/wiki/Passive_differentiator_circuit but this description immediately jumps into heavy maths, so unless you're a mathematician or physicist, don't bother with it. In...
  4. KrisBlueNZ

    dimmer for parallel or series LEDs with timer

    In addition to what Steve has told you and asked you: The symbol you're using for your LEDs is wrong. Do you know the total current consumption of your LED circuit? I expect it's more than 1A. What behaviour do you want? "A dimmer and timer" is not detailed enough for anyone else to know what...
  5. KrisBlueNZ

    understanding an RC toy mainboard

    I have no experience with RC stuff so take this with a grain of salt. The usual way a motor is driven is called an H-bridge. See http://en.wikipedia.org/wiki/H_bridge This arrangement allows the motor to be driven in either direction. If PWM (pulse width modulation) is used, the motor speed...
  6. KrisBlueNZ

    sound to electricity

    FYI an interesting video covering two Linear Technology devices for energy harvesting from thermoelectric and solar cell sources:
  7. KrisBlueNZ

    Newbie Help

    FYI an interesting video covering two Linear Technology devices for energy harvesting from thermoelectric and solar cell sources:
  8. KrisBlueNZ

    Readily Available Energy

    FYI an interesting video covering two Linear Technology devices for energy harvesting from thermoelectric and solar cell sources:
  9. KrisBlueNZ

    Mysterious diode identification help!

    As long as it's from the mains input path, and it has four connections and two windings, it should be suitable.
  10. KrisBlueNZ

    Mysterious diode identification help!

    T1 burnt up? That's the component in the bottom right corner next to where the mains comes in? If so, it was probably faulty. There's not much that can go wrong with a common-mode choke that will make it burn up, apart from some kind of breakdown between the two windings. Its function is just...
  11. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Yes...
  12. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    I recommend you use the 10,000 uF 63V capacitors you found, if they will fit.
  13. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Voltage rating isn't an issue as long as the replacements are equal or higher. Using higher capacitance replacements will cause that side effect but really I would not worry about it. Using higher capacitance will provide more sustained energy for peaks but I doubt the difference would be...
  14. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    They should be OK. They will put a slightly higher load on the rectifier diodes at the moment you turn on the power, but it's unlikely to cause any problem.
  15. KrisBlueNZ

    Ohm's Law Conundrum

    Yes, you're right that in most cases, resistance is determined by characteristics of a physical component, and is pretty much constant. A component of this type, such as a resistor (obviously), is called "ohmic", and its resistance determines the ratio between the voltage across it and the...
  16. KrisBlueNZ

    led heartbeat

    The design at http://img822.imageshack.us/img822/6900/ledheartbeat1fading.jpg has a number of problems, too many for me to bother going into. Even with those fixed, it won't produce a very realistic heartbeat effect.
  17. KrisBlueNZ

    Darlington Pair (Easy question answer ASAP)

    Asking about the difference between those two circuits is like asking about the difference between a spider and a horse. The first circuit demonstrates a Darlington pair controlling a light bulb. When the switch is turned ON, a relatively small current flows into the base of TR1, and is...
  18. KrisBlueNZ

    help identify a capacitor

    The 821 in the part number MIGHT mean 820 uF...
  19. KrisBlueNZ

    9v preamp for acoustic guitar

    Normally, wires have their own holes. And it's normal to put the holes for related wires in the same area, and connect them into the rest of the circuit using tracks. So, for example, the two wires that go to the pickup should connect to two pads that are next to each other. That's the...
  20. KrisBlueNZ

    LED Driver with 3 wire input

    Manufacturer? Model number? Have you googled it?
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