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  1. duke37

    Pioneer SA-505 clicking

    You give links to C2679 transistor and A1104. The 2C2679 is a npn very high frequency transistor in the small TO-92 package. 19V 50mA.This is unlikely to be used in an amplifier, it would be used in a VHF radio. The 2SA1104 is a power transistor (120V 5A) in a TO-3P package and would be fixed to...
  2. duke37

    PSU advice

    That looks OK. I put a switch across the light so that I do not have to remove the device when full power is required.
  3. duke37

    Pioneer SA-505 clicking

    Find out if they are npn or pnp by looking at the number or testing on a transistor tester. The tester will also tell the correct connections. Get a schematic (circuit diagram) to see what is connected where. It depends on the circuit as to what could be damaged.
  4. duke37

    Powering one 12v device from two 12v sources

    If you are connecting directly to the battery, make sure it is fused. A battery can start a fire very easily if the wire insulation wears through.
  5. duke37

    Powering one 12v device from two 12v sources

    You need to find the current drain. The MR 5100 is a Schottky diode, 100V 5A The 1N4007 is a 1000V 1A diode. Either of these will do if the current is less than 1A.
  6. duke37

    Hello, varactor(varicap) formula help

    Look up Wikipedia which shows the internal structure and circuits to supply the bias voltage. The graph of the capacitance against bias voltage is far from linear. The AC voltage should be less than the bias voltage. The diodes were often sold as three matched devices. What do you want the diode...
  7. duke37

    Hello, varactor(varicap) formula help

    I looked up the Telefunken bb205b diode. The data says 1.8 to 17pF. The 1.8pf will be at maximum voltage and the 17pF at minimum voltage.
  8. duke37

    Nichrome wire heating project. help please!

    I do not think you can measure the temperature of the wire directly since the thermocouple will affect the reading. You could measure the resistance of the wire and control it to a standard value. Some complication here.
  9. duke37

    Powering a wireless door chime transmitter.

    The current demand will be low if designed to be run from a battery, you ahould measure it. Almost any power supply will be able to provide 1A, just make sure the capability is above the demand.
  10. duke37

    Powering a wireless door chime transmitter.

    I do not think that a bell push should consume any current when the button is not pressed. Can you measure the current when the button is released and when pressed. If the device runs on a 12V battery, then a 12V DC power supply will do but make sure it is 12V not way above. Also connect the...
  11. duke37

    Led lighthouse

    The arduino (never used one) will not give out 9V, it will be run from 3.3V or 5V. 5V is necessary to turn on the irl520 logic level fet. A low value resistor from gate to source will reduce the drive voltage.
  12. duke37

    Led lighthouse

    A fet has a very high input inpedance and the gate voltage will stay where it is put if not connected to anything else. Does the output of the arduino provide sufficient voltage to switch the fet?
  13. duke37

    Step down transformer reference list?

    I looked up Maurtius and the information was 230V 50Hz, so why do you want a 240V transformer unless the supply is the same as in the UK where the standard voltage was changed from 240V to 230V to agree with the rest of europe. In practise, the tolerance was increased so no changes were made...
  14. duke37

    Step down transformer reference list?

    A small increase in voltage should be tolerated by the transformer, however, a 60 Hz transformer will also be stressed by running on 50Hz. You do not say what frequency you have in Mauritius or whether the transformer matches this. Small tranformers have poor regulation so the output voltage is...
  15. duke37

    Lead-acid vehicle battery discharge time

    The voltage to charge the battery should lie between 13.8 and 14.2V. 14V is a good value to aim for. My neice had a low charging voltage and changed the alternator with no improvement. The problem was a poor, rusty earth connection. If you get the voltage up at the battery terminals you will not...
  16. duke37

    Lead-acid vehicle battery discharge time

    I think this is impossible to calculate. A petrol engine needs a certain voltage for the ignition, the voltage is lowest at TDC when the spark is required, this is alleviated if a capacitor discharge ignition is fitted since the capacitor is charged before the maximum current drain. I think...
  17. duke37

    Inverters

    A 20V transformer can be used to subtract 20V from the invertor output. The motor may not like a non sine supply. What does your invertor supply?
  18. duke37

    DT9205A multimeter is not switching on after measuring the DC voltage. Can any one help me?

    You have not given the specifications of the meter. If you are measuring over 1000V on a 1000V range, then you may have popped it. It may be possible to reset by removing the baattery for a few minutes. I have a cheap digital meter which fizzed when 600V was applied on the 1000V range. Luckily...
  19. duke37

    Underdriven 12V LED chips in a 120VAC system

    D1 and D3 will steer the supply to the two loops. D2 and D4 are not required. A fat resistor should be included to control the current. If you wish to drive the leds with 20mA average, then a resistor of about 100V/20mA = 5kΩ. from the power supply. Power = I*I*R = 2W, use a 5W. Any high...
  20. duke37

    "Coughing" Polk Audio PSW202 subwoofer

    If the applied voltage is under 30V, then 35V capacitors are adequate. If the voltage is over 30V, then go to 50V capacitors. Capacitors have various faults, they can leak or have a large internal resistance (ESR) or low capacitance. If the amplifier works at all, it may not be leakage. Low...
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