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  1. duke37

    Common Terms

    1. In the days of yore when there were scanning TVs, the spot traversed the screen from one side to the other and then had to flyback to the start side again. In order to do this rapidly a large voltage was needed at the scan coils. A special transformer was necessary to provide this high...
  2. duke37

    Very Basic FM radio help

    Glad to know you have had some success. FM radios need a certain level of signal input and the quality of the output does not improve much above this. The aerial you have is called a dipole and is broadly tuned to the frequency you want. I suggested that you made each side of the dipole 2ft...
  3. duke37

    Very Basic FM radio help

    Better eyes than mine might make out the tracks. In the third picture, there is a large track area in the top rifgt corner, this could be ground. You appear to be holding a headphone socket, this will have a ground connection to the body of the plug. The tuning capacitor will also have a...
  4. duke37

    Very Basic FM radio help

    The aerial should be in the shape of a T. This is called a dipole. Tape the wires to a five foot bamboo and take the cable from the middle at right angles. Your photos are better than average, if you show the track side of the board, we may be able to spot the ground track.
  5. duke37

    Voltage Regulator not regulating?

    These regulators do not like a voltage being placed across them in the wrong direction and a diode is often placed across the regulator to protect it. If you had connected it up the wrong way round it could be popped off. Try the 7505 and get that to work, then change to the 7812 again.
  6. duke37

    Very Basic FM radio help

    Don't be sorry about the questions, that is what we are here for! I think there might have been a bit of a disaster, the coil seems to be connected to the board at each end and so is likely to be part of a tuned circuit. If it has been changed in shape, it will be off tune. The rod aerial...
  7. duke37

    60v too high

    This is the idea I had, perhaps others could comment.
  8. duke37

    gps and audio

    Isn't GPS receive only?
  9. duke37

    60v too high

    This is possible, you would need two equal resistors (1k?) in series with the centre connection going to a pair of npn transistors in darlington connection and also a pair of pnp transistors. The emitters should be connected together as the virtual earth. In theory, the net current should be...
  10. duke37

    dark detector using 555 timer

    Assuming the circuit works as it should but with the wrong sensitivity, increasing the 4.7k resistor will give more sensitivity and decreasing it less sensitivity. You could cosider replacing the resistor with a potentiometer to set the sensitivity to where you want.
  11. duke37

    60v too high

    This would be possible but would not be worthwhile and any fault in the control circuitry could finish the amp. If it is a transformer with visible laminations, it could perhaps, with dedication, be rewound with 60% of the original turns. If it is a toroidal transformer, this will be too difficult.
  12. duke37

    Voltage Regulator not regulating?

    Stating the obvious, check the output voltage before connecting the amplifier.
  13. duke37

    Very Basic FM radio help

    Yes, you are corect. Connect the inner to the original aerial connection and the outer to the ground track. The ground track will go to many places on the radio and often goes round the outside of the board. It will connect to the negative of the battery and the negative of several...
  14. duke37

    Very Basic FM radio help

    The telescopic aerial is shorter than optimum so it is tuned with the extra coiled wire. There needs to be two connections to the aerial, the other is the ground connection of the radio which is usually a larger track on the printed circuit and connects to most parts of the radio. Connect the...
  15. duke37

    Are Ferrite Toroids inductors

    No, ferrite torroids are just rings of magnetic material. They can be used to produce inductors by winding them with wire. They will only be added to circuits if they are significant. There are many kinds of inductors and the choice depends on a multitude of factors.
  16. duke37

    tachometer.

    It looks as if it is working. When you touch the input with your finger, you are putting in mains hum, 50 or 60 Hz. I hope you have a protection circuit in the input. A signal generator would be ideal to set up the calibration. Good luck.
  17. duke37

    Adding lights to lawn tractor

    You may not have the optional 12V DC output. The DC output of the alternator is only 3A so, after recharging the battery, there will be very little left over so the output current will come mainly from the battery.
  18. duke37

    Adding lights to lawn tractor

    The electrical system is not the most sophisticated. The lights you want do not specify voltage or current, I expect they will be 12V. The alternator does, as I ruminated, run the lights on AC. Adding extra load on the system may give less light or may overheat the alternator windings. The AC...
  19. duke37

    what does this circuit suggest??

    It looks like as if it could be a multivibrator to me also, what I see as a first look. The 2N2222 has a negative supply on its collector. I do not fully understand the op-amp circuit - that will take some thought. It is not the usual mixture of positive and negative feedback. The loop C3...
  20. duke37

    Adding lights to lawn tractor

    I agree with Dave that there might be a limitation on the power available. Vehicle alternators generate AC and rectify this with diodes which drop some voltage. This small waste of power may not be important with a large engine. Your low powered tractor may rectify the AC to charge the battery...
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