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  1. duke37

    Ignition Coil Driver Questions

    I would get rid of the snubber and put a capacitor aross the fet instead of the 1N4005. The energy in the coil will be 0.5*I^i*L and this will be transferred to the capacitor 0.5*V*V*C. V=I*sqrt(L/C). This is how the traditional ignition worked. A dodgy capacitor would give unreliable fireing...
  2. duke37

    Heathkit AR-15 receiver - problem with multiplex circuit

    I cannot pretend to understand the circuit but a locked oscittator will need a good signal to lock it and if the signal has insufficient amplitude or wrong impedance then lock will be lost. Obviously any drift should be investigated.
  3. duke37

    Ignition Coil Driver Questions

    The snubber circiut is there to absorb the energy in the circuit when the fet is turned off. This limits the drain voltage. I presume that you want a large voltage output so the voltage should be limited by the spark gap. Primary current is determined by the coil resistance and inductance. If...
  4. duke37

    Vacuum Cleaner Problem

    You only need to unsolder one lead. The reading will vary a bit and a digital meter may give rapidly changing digits which cannot be interpreted. If the armature has partially burnt out, then there will be open circuit at one position. When turning the motor, put a sideways force on the pulley...
  5. duke37

    Vacuum Cleaner Problem

    The reason I went for motor trouble was the voltage at the motor was higher when it was not working indicating no current going into the motor. This reasoning is at conflict with the mechanical theory. Disconnect the motor and measure the resistance across its terminals with an analog meter...
  6. duke37

    Vacuum Cleaner Problem

    If the voltage rises when the motor stopps. then there is a break in the circuit. Possibly worn out motor brushes. The motor probably has brushes since it is fitted with the interference suppresion chokes. Nice photos!
  7. duke37

    Solenoid Motor Strength

    You could look at ludens.cl/electron/transfos/transfos.html "Practical transformer winding." Ludens works in modern units only. He says that 1T is the maximum strength of the field. You mayl need a steel bar about 30mm diameter to get the field. The diameter of a coil 150mm long can be...
  8. duke37

    Common ground

    You have created a short due to the centre tap connection. You can get what you want (I think) by using a bridge rectifier on the transformer outer connections. This will give 24V rectified. The transformer centre tap will give a mid point voltage.
  9. duke37

    Determining AM transmitter power output

    You could measure power in and then estimate an efficiency of say 50%. Put the power into a dummy load such as a Heathkit cantenna and measure the rate of temperature rise. Put DC into the camtenna and adjust the voltage to get the same rate of temperature rise. It is a strange transmitter...
  10. duke37

    Powering LED strip

  11. duke37

    Powering LED strip

    I have a Heathkit transceiver which uses a reversed transistor as a zener diode so it can work but over driving the base such as in a two transistor bistable oscillator can cause long term changes. A 4093 can operate from 3V up to 15V and give sufficient output power to drive a medium power...
  12. duke37

    Powering LED strip

    The circuit you show uses breakdown of the transistor when connected the 'wrong' way round. This is not good for the transistor. Too low a voltage will not cause breakdown so it will not oscillate. I would use a CMOS 4093 as an oscillator and a transistor to power the strip. A capacitor and...
  13. duke37

    Nichrome wire heat up

    If you are changing the wire guage, then you can get details of resistance per metre to suit. The resistor will depend on the length. Give us details of the power supply and show us a picture of what you are trying to do.
  14. duke37

    Nichrome wire heat up

    You are taking too much current for the fuse. Two similar pices of wire in parallel will take double the current of one. You could try running them in series but may not have sufficient voltage.
  15. duke37

    Water level meter

    AC will not guarantee hat there is no corrosion. A capacitance probe could be made from a piece of insulated wire and energised with high frequency signal. A special detector circuit would need to be used.
  16. duke37

    How can I make Audio Amplifier from 2SK3549-01 MOSFET

    You could try placing a high value resistance from the 3.3V supply to the fet base. Then drive the base through a capacitor so that the signal is centred about 3.3V. Make sure that excessive current is not passed or something my fail, the speaker is what controls the maximum current. A resistor...
  17. duke37

    does anyone understand microphone wiring

    I have not seen a switch with the side comtact. My guess is that the top wire is a power wire to energise one side of the microphone. Look up Wikipedia to try and find the type of microphone.
  18. duke37

    Astable 555 500Khz 20ms

    I am not sure what you want to do but to get a 500 kHz (not KHz) square wave I would use a 1MHz crystal oscillator and divide by two. The 555 would be used to turn this on and off. You have two 1N4004 diodes in series. You only need one or none.. The 1N4004 is a slow speed diode, you would be...
  19. duke37

    does anyone understand microphone wiring

    My guess is that the microphone is slowly discharging when the switch is turned off
  20. duke37

    How can I make Audio Amplifier from 2SK3549-01 MOSFET

    What is your normal language? Barley only rustles when the sun is on it.:) What is I1? What are the specifications for the FET? If I1 is low, then there will not be enough voltage to turn on yhe active devices. As drawn, there will be 0.6V less then I1 on the fet gate which may not be enough...
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