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  1. Alec_t

    Keyless and contactless Reset switch

    ..... and provided the reed switch is able to handle making/breaking a high enough DC current when supplying a load which could be resistive/capacitive/inductive.
  2. Alec_t

    B&O Beogram 1900 bad motor?

    If a rubber pinch/drive wheel or belt has disintegrated, is it possible that the motor is spinning but simply not driving anything? Can you tell if the actual motor shaft is rotating?
  3. Alec_t

    Project related inquires.

    Yes. The JFET would need a gate voltage below the ground rail to turn it off.
  4. Alec_t

    amplifier circuit(2N3904) giving no sound

    Welcome to EP! Your amplifier is really only a 'pre-amplifier' and is fine for small signals but can't provide enough current to drive an 8Ω speaker. You need a power amplifier. Google should find you many circuits to try.
  5. Alec_t

    Acceptable Zener regulator tolerances

    Hmm, the zener voltage in that circuit doesn't seem critical. If it were, say, only 25V then you'd be dropping an extra 2V across the feed resistor, i.e about 4% of the 50V(?) main supply. That would cause slight additional heating of the resistor, which may or may not be rated to cope.
  6. Alec_t

    Acceptable Zener regulator tolerances

    Depending on the circuit the zener is in, its value may not be critical. Can you post a schematic?
  7. Alec_t

    Digital piano won't power ON

    Nice one!
  8. Alec_t

    LED street lights

    ..... and it isn't a single LED; it's an array of LEDs on a heatsink.
  9. Alec_t

    Varying voltage

    Welcome to EP! Your PC fans are probably already controlled by the PC, using a PWM technique rather than simply varying the fan voltage, so you would need to avoid interfering with that. How exactly do you plan to use the potentiometer to control speed?
  10. Alec_t

    LTspice boost circuit simulation

    The .asc file netlist contains references to paths on your C drive, which are preventig the sim from running on my PC :(.
  11. Alec_t

    LTspice boost circuit simulation

    Can you post the .asy files for the symbols?
  12. Alec_t

    Cheap linear actuators

    Careful! That's the down-pipe from the upstairs toilet lurking behind there :).
  13. Alec_t

    Digital piano won't power ON

    Yes.
  14. Alec_t

    Hall effect controlled fuel injector

    Won't the lead time need to be changed as the rpm increases?
  15. Alec_t

    Digital piano won't power ON

    That will concentrate the heat in one board area instead of having it spread over two areas, so you may need to space it a bit further from the board than before, to avoid cooking the board.
  16. Alec_t

    Emerson MW8779W doesn't heat but turns on!

    Seems rather low. I've just measured 2.3Ω primary winding resistance on the MOT tranny in my junk box.
  17. Alec_t

    Hall effect controlled fuel injector

    What do you have in the way of power supplies for this project? If the injector coil has significant inductance you may need quite a high voltage to get sufficient current to open the injector in <1ms. The LM1949 is rather long in the tooth, so may not have been designed to cope with such brief...
  18. Alec_t

    N channel Fet v npn

    If Vgs is only at the threshold, Vgs(thr), then only a few microamps of drain current flow (check the datasheet for the actual value). Higher Vgs = more current.
  19. Alec_t

    Slip up!

    Possibly, but I don't know. I've never used the stuff, but personally I would avoid anything described (according to online sources) as "a lubricant fortified with PTFE". Electrical contact cleaners are usually solvent-based (e.g. acetone, methanol).
  20. Alec_t

    Voltage Regulation for charging Supercapacitor

    The transistor acts as a shunt to pull the voltage applied to the cap down when it tries to go above a threshold value. In this circuit the threshold is set by D1, D2 and the transistor base-emitter junction, which are all in series. Since they each drop about 0.6V to 0.7V, the threshold will be...
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