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  1. duke37

    Joining transformer wirer

    There must be a high standard of insulation of the coil from the pole piece. The pole piece should be grounded (earthed). Thre should be no difficulty with arcing if the DC is provided with a bridge rectifier placed across the coil. This will act as a flywheel diode, so switch the AC input to...
  2. duke37

    Radiogram, no sound

    Do not disconnect leads leading to the speaker. If you disconnect the secondary of the output transformer, then very high voltages can be produced which may break down the insulation either in the valve base, in the output transformer or any tone corection capacitor. If you disconnect the...
  3. duke37

    Why do these transistors overheat?

    Comments 1.Connecting two power supplies in parallel will only work if they are trying to do the same thing, however, I think that you are not connecting them in parallel. 2. Each 2N2222 pulls it collector low when switched on and should allow its collector to rise to 12V when switched off...
  4. duke37

    Radiogram, no sound

    There could be four problems. 1. A bad valve 2. A leaky capacitor feeding the grid P2 3. A poor high voltage supply to the anode. 4 A leaky valve holder. You did not measure the total current through the valve by measuring the cathode voltage. You MUST MUST MUST keep the grid voltage down, you...
  5. duke37

    Problems with Royer oscillator and an aircore transformer

    As I understand it, the transistor current rises until the transistor runs out of breath! Then the collector voltage rises and the opposite transistor is turned on. An iron core may saturate first or the transistor gain will drop first. In any case, with sufficient loop gain, the circuit should...
  6. duke37

    Problems with Royer oscillator and an aircore transformer

    My thought is that you do not have swufficient base drive. Either use a centre tapped drive winding with centre tap to ground or place diodes across the base/emitters of the transistors. The diode circuit is described in the Mullard transistor circuit book. It allows the base to be driven...
  7. duke37

    Transformer output

    But only approximately. A transformer is made to give its rated output when on load so the voltage off load will be high, from 1% (big transformer) to 5% (small transformer). This is known as regulation in the jargon. When run in reverse, the unloaded output will be low and will drop further...
  8. duke37

    Motorbike KERS problem

    The bridge diagram as shown is correct but when the diodes face each other on the heat sink, the anodes will be on the right on one row and on the left on the other row. The amount of linkage wire should be minimal. Have you got this right? The positive output will be connected to three cathodes...
  9. duke37

    Motorbike KERS problem

    What you want is very low diode voltage drop, smaller diodes will have a higher voltage drop so will not help. You could get the data for the diodes you have and work out the speed needed to overcome the voltage drop. Below this speed there will be negligible braking. Remember that the current...
  10. duke37

    Motorbike KERS problem

    "Hooking the output of the regulator up we get 5V which is expected from the 200kv motor" 200kV - that is some motor:) Any leakage in the diodes will add, not detract from the braking effect. The diode voltage drop will be significant at 5V input. Have you got the diode bridge connected correctly?
  11. duke37

    Powering a mobile FM transmitter

    If it runs off 12V, then a battery will provide this directly, however, a battery will provide very high currents if allowed which can cause damage and fires. The battery connection should be fused close to the battery and all cables should be properly insulated and protected. Make sure the...
  12. duke37

    Reed switch

    You say The reed switches I require is 21 v DC no . If the no means normally open, then the reference you give to the reed switch is no good, these are normally closed. I would think that normally closed reed switches would be used since if the visitors clipped a wire, the alarm would...
  13. duke37

    Reed switch

    Perhaps you are getting confused between a reed switch and a reed relay. A reed relay has a reed capsule surrounded with a coil to provide a magnetic field. This coil has a specified voltage. A reed swich has just the capsule and needs to be placed close to a magnet to activate it. I would think...
  14. duke37

    Radiogram, no sound

    To translate, B+ is the high tension voltage. The plate is the anode. EL84 1 - 2.Grid 1 3.K Cathode 4.Heater 5.Heater 6.- 7.Anode 8.- 9.Grid 3 (screen) If the anode does not have a high voltage on it then a lot of current could go to the screen and damage it by overheating. The grid (P2)...
  15. duke37

    What resistors should I use to reduce power from 120v outlet

    Have you still got a younger brother? Do not teach vulnerable people dangerous practices. Get a power supply (wall wart) which gives the voltage you require without the danger of playing with the mains.
  16. duke37

    Need to understand power rating.

    There is a problem with english, I think he has a petrol engine, not a gas motor!:) Small motor cycles often have an alternator with no voltage limit. The current is limited by the leakage inductance of the alternator, thus they will produce the right voltage when loaded with the right bulbs...
  17. duke37

    electric motor

    Even if you cannot do a good picture, try showing us a bad picture. If you cannot do that, copy the label on the motor with all the details. How have you managed without coffee if the grinder is faulty?
  18. duke37

    Joining transformer wirer

    To keep the power to a minimum, the space should be filled, you can either use thin wire, lots of turns and lots of volts or thick wire, few turns and few volts. The ampere turns should be the same. Making the device longer will not affect the necessary number of turns or the current, it will...
  19. duke37

    Question regarding electromechanical piano wiring

    I would think that running in parallel would be better than running in series and it looks to me that this is how it is wired. Having large loops of wire could introduce noise so I would experiment with one octave feeding a virtual earth amplifier and then adding four other octaves. How does...
  20. duke37

    electric motor

    Bench grinders are normally driven by induction motors - quite simple. Angle grinders are usually driven with universal motors which may have speed control - complicated. A pretty picture would help us to make suggestions.
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