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  1. duke37

    Voltage regulator voltage too high

    Why not look up the data sheet? Try a 100nF cap on the output and more on the input.
  2. duke37

    Electrolyte-less Capacitor

    Most capacitors do not have an electrolyte. Most have a dielectric, this may be vacuum, air, plastic or aluminium oxide in electrolytic capacitors. Voltage is limited by the breakdown of the dielectric. Vacuum is best, modern plastics are very good and the dielectic constant is much higher than...
  3. duke37

    RF basics

    Standing waves will dissipate energy. Standing waves will present a different impedance depending on the position of the wave. Altering a cable length may change or even stop the equipment working.
  4. duke37

    X2 extreme automotive battery charger repair

    Show us some pictures of the circuit board where the choke should be. If the boerd is broken, it can be repaired with epoxy and broken tracks can be mended with wire. I mended an electric fence (twice) where the wire had got caught up in a plough and the board was broken into two. They now use...
  5. duke37

    Can someone help me sort these 2 hot resistors ?

    You need a circuit diagram, Does it work? The resistors are close to the output transistors so they may be linked. Check the output transistors for shorts. There are enough transistors for a stereo set so you could compare the voltages on one channel with the other. Use a lamp limiter to reduce...
  6. duke37

    RF basics

    Try to find some basic books on radio frequency principles. A steady RF signal, the carrier frequency, conveys no information other than the sender has money to spare. The carrier can be modulated by altering the ampltude of the carrier. This is used on long wave, medium wave and short wave. The...
  7. duke37

    Which is better for led

    The leds are specified for voltage and current, perhaps they have a control circuit built in. Red leds can need a voltage of 2V or so and other colours more. There may be several leds connected in series to get up to 10V. Leds can be driven using PWM pulse width modulation. Say you have a 24V...
  8. duke37

    Need help for value of resistor

    There will be limit to the speed at which the switch will turn off which will depend on the characteristics of the switch and the Miller effect. Therefore I would think that any diode would do. The UF4007 is faster than the 1N4007 and can pass an Amp.
  9. duke37

    Need help for value of resistor

    Sorry that I specified 1N2007 instead of the correct 1N4007. When the relay is energised, it will have 12V across it and a current determined by the resistance. When the relay is turned off this current has to go somewhere until the inductive energy is dissipated, the diode will do this. If the...
  10. duke37

    Assistance in decoding a circuit diagram

    What meter have you? A digital meter will have a resistance capability so you can determine whether two pins are connected together. It may also have a capacitance range to determine the active pins.
  11. duke37

    Need help for value of resistor

    Why are D3 and D4 different? I would keep a stock of 1N2007 for all situations such as this.
  12. duke37

    Assistance in decoding a circuit diagram

    C3 is a 0.1uF (100nF) capacitor and is almost certainly non-polarised so can be connected either way round. How do you define the positive side?
  13. duke37

    Newbie question...

    Wire wrapping is not normally soldered, they are used in vibrating situations. The wires can be added and disconnected with the appropriate tools (expensive) so can be used as a permanent bread board. If your wires have been soldered then you have problems to disconnect them. Replace with a...
  14. duke37

    Sensors to detect and locate a fire

    Fires usually flicker and this component could be used to distinguish from a steady heat source. LEDs however are often driven with a high frequency intermittent supply even if they appear steady. It may be possible to distinguish by filtering, low frequency for fire, high frquency for LED.
  15. duke37

    24 Volt DC Transformer to AC mod ?

    What is the load? If the load is a transformer, then AC is mandatory. If the load is a bridge rectifier, then DC would be OK.
  16. duke37

    Help me in calculating base resistance for transistor

    I have not looked up the logic of the 4017 to see if it connected correctly. If IC2 is not powered, it may be using power from the 555. Try a capacitor across IC2 supply.
  17. duke37

    Convert 24vdc charger into 125vdc charger

    There seems to be two posibilities. 1. Rewind the transformer to give the required voltage (expensive) and change the diodes (cheap). 2. Add smoothing capacitors (1mF/A?) and use a boost convertor. I have not investigated high power convertors.
  18. duke37

    Video signal amplifier.

    Why is this? If the cable is matched at the load end, there will be no reflections to be absorbed and the cable will appear as a resistance equal to its impedance. A resistance at the source will just waste power.
  19. duke37

    Need help resistor values

    I have been told that I have bats in my belfry:).
  20. duke37

    Need help resistor values

    I am sorry if you are upset, there is no intention to put you down. It is quite normal to examine a circuit and simplyfy it. In your case an active circuit is not needed at all, this was spotted when the operating conditions were known fully. I have some kmowledge of simple electronic circuits...
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