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  1. duke37

    reducing 5V to 4v or 4.2v MAX

    The 1N5408 is a common standard diode. You can probably find voltage drop on the internet which may be much faster than mine. The heat generated will be the same for the same voltage drop. A drop of 1V at 3A will generate 3W whether it is with a pair of Schottky diodes, LDO regulator, a...
  2. duke37

    Hi everyone! Can i ask why is there a diode here?

    Q3 seems to have gone missing. Q2 and Q4 form a multivibrator oscillator with the buzzer setting the frequency. The whole of the buzzer current goes through the base of Q2. This seems to be wrong. I do not know the purpose of the diode, perhaps it has something to do with the missing Q3.
  3. duke37

    reducing 5V to 4v or 4.2v MAX

    A single 3A silicon diode would probably do what you want. 1N5408
  4. duke37

    Energy Lost Due To Friction

    I know of no direct link between friction and electronics but I spent much of my working life persuading instrumentation to measure friction of braking materials. In some cases, the friction was negligible when wet and in other cases could be quite high when the friction material was on fire.:)
  5. duke37

    Energy Lost Due To Friction

    There are various ways of calculating however, the friction and hence acceleration will not be constant but will depend on speed. This means that the a sophisticated method of measuring the velocity at the end of the trip will be advantageous.
  6. duke37

    Energy Lost Due To Friction

    The speed at the end of the descent will be double the average speed if the acceleration is constant. Otherwise it will be necessary to measure the speed over the last mm or so.(difficult). Measuring the slowing due to the friction can give the retarding force, the energy will then be force x...
  7. duke37

    Energy Lost Due To Friction

    You start with zero kinetic energy and end with kinetic energy dependant on the speed. The initial energy is the potential energy. A bit of subtraction gives the energy lost in the friction. You are not asked to determine the coefficient of friction, just the energy lost.
  8. duke37

    Repairing my old Wega V-3840-2 amplifier

    Try to get a circuit diagram.
  9. duke37

    Repairing my old Wega V-3840-2 amplifier

    I would vote for a faulty power supply electrolytic capacitor, These will allow AC to get at the amplifier and will arc over inside with a pop, then recharging again and maybe working for a while. If the diode is to set a temperature compensated static current, then it can be shorted until the...
  10. duke37

    Energy Lost Due To Friction

    You do not say what the starting velocity is. I assume it is zero. The potential energy can be got from the height. The time of flight will give the average velocity. If the acceleration is constant, then the final velocity will be twice the average velocity. Calculate the final kinetic energy...
  11. duke37

    20kv Multiplier

    Glass is a good insulator but cannot be machined. It is often used for overhead electrical distribution. Polyethelene is good and used for water pipes, it can be cut easily. Bare glass fibre/resin printed circuit board is good but you may not find it big enough. Cheap PCB will often absorb water...
  12. duke37

    Modular house - intercoms won't work from front to back.

    A decent capacitor will not disipate any significant amount of power. The current is out of phase.
  13. duke37

    20kv Multiplier

    Your diagram is neither schematic or practical layout. If it is a schematic, you should use the conventional capacitor symbol. If it is a practical layout, you need to show how the capacitor stacks are built with high quality insulation support.
  14. duke37

    Any way to check D1889 & B1340 transistors, apart from measuring resistance?

    What are the data for the transistors, they are probably not special and some equivalents could be found. Many meters have a little socket with which to connect transistors to measure their gain. If they have any gain at all, they are possibly OK.
  15. duke37

    20kv Multiplier

    You could look at the following http://www.extremeelectronics.co.uk/electronic/cockcroft-walton-voltage-multiplier/ The capacitors should be in two stacks and the diodes will be cross connected between them. You could look at a Tesla coil to get the voltage directly, this will be AC whearas...
  16. duke37

    20kv Multiplier

    Why go for a C/W multiplier? If you want fewer stages, you will need higher input voltage, 5 stages will need an input of 4kV. Look up the cost of high voltage diodes and capacitors. Why go for the multiplier, I would go for parts out of a CRT colour TV. These often run from 12V, use a high...
  17. duke37

    I cant step up voltage

    Look up shaded pole motor on Wikipedia.
  18. duke37

    Frequency conversion from 400 Hz to 50/60 Hz

    If it can be modified, can it be run on DC, rectified from the 400Hz supply?
  19. duke37

    I cant step up voltage

    To use a motor as a generator, you will need one with a permanent magnet rotor. A fan heater motor is likely to be a shaded pole motor with no permanent magnetism and hence no output.
  20. duke37

    20kv Multiplier

    It depends on what you want. What output do you want? What is the power supply, voltage and current? How much do you want to pay? !000V diodes are fairly cheap and would be able to handle 250V input, Use fourty of these. 1N4007 would suffice at 50 or 60Hz. The capacitors will need to be fourty...
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