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  1. duke37

    gain amplifier

    You can determine this if you look up the data. Thats obvious. The TL071 needs a plus and minus supply.
  2. duke37

    gain amplifier

    Do the amps need a plus and minus power supply? The gain will depend on the potentiometer setting.
  3. duke37

    Radiogram, no sound

    Coloured wires do not help much. Measure the DC voltage relative to chassis both sides of R40. Measure the cathode voltage (pin 3) of V5, the EL84. It should not rise above 8V. if it goes above 10V, then switch off. Measure the anode voltage of V5. If these are all correct, then you shoud...
  4. duke37

    transformer doubt

    Adam The current in an unloaded transformer magnetises the core and in normal use, the current reverses and the core magnetisation reverses giving an average of zero. If the transformer feeds a half wave rectifier, then the current is offset from the mean and it can be considered as an AC...
  5. duke37

    transformer doubt

    It is better to use a full wave (bridge) rectifier since this does not put a DC component in the transformer. Transformer cores can be saturated if DC current pushes the magnetic flux to "one side" and then the primary current is limited only by the wire resistance - boom. Diodes are very cheap.:)
  6. duke37

    LTspice, Warning node is floating

    I found that I had to tick to put into original location before I could bodge it. I was wrong there are no capacitors there. There is however a floating wire connected to V108A and labeled 3.3V
  7. duke37

    LTspice, Warning node is floating

    I cannot read the schematic properly but it looks as if there are two capacitors in series, bottom left. There is no DC connection to the junction, use a 100M resistor across one of them.
  8. duke37

    Radiogram, no sound

    Measure the DC voltage across the primary of the output transformer and calculate the EL84 anode current. Measure the voltage on the primary of the output transformer relative to chassis, this will tell you if the EZ80 is doing its thing.
  9. duke37

    RF circuit , mixer help

    It depends on its frequency and whether the frequency is constant. The normal way for a constant RF frequency is to split the signal into +45 and -45deg. This is done by feeding through a resistor to a capacitor and through another resistor to an inductor. For a band of audio frequencies...
  10. duke37

    Radiogram, no sound

    Replacing the rectifier will energise the set but I would be very surprised if it would cure the problem. You need to measure voltages without killing yourself to see if they match the circuit diagram. Make sure the EL84 is not passing excess current either by measuring the cathode voltage or...
  11. duke37

    Measuring current using current transformer ring type

    It is some years since I used LTspice and it is not on my present computer. The inductance of the transformer looks very low but whether this would have an effect in an ideal situation, I know not. If I remember rightly, the source is 500A peak, the transformer has a turns ratio of 32 so that...
  12. duke37

    Radiogram, no sound

    Yes, the EZ80 is the high tension rectifier, removing this will stop everything working except the dial lights Pontefract is a bit far, I will have to satisfy myself with a Pontefract cake.:)
  13. duke37

    RF circuit , mixer help

    "Much bigger". That is because the source is 100k and the load is under 20k. You still have not shown the output of the mixer. This would be the two sources of M1 and M2 connected together. The oscillator drives M1 and M2 in opposition so the output is zero until the current is varied by M3...
  14. duke37

    Measuring current using current transformer ring type

    I think that a bridge rectifier before the burden resistor will do all that an active rectifier will do with much less complication and no power supply required. If the signal from the burden resistor is fed through a 100k resistor into a 10μF capacitor to get the mean, then the ADC can be quite...
  15. duke37

    RF circuit , mixer help

    Which is the interstage capacitor? Do you mean C6? It is being fed from a source of 100k and feeds into under 20k so would expect about a fifth of the voltage when connected which is about what you have. What are all the inductances for, they do not seem to be lead inductances since they all...
  16. duke37

    Radiogram, no sound

    The first thing to do is to check that the EL84 is not passing too much current. I have not got the circuit but would expect that the cathode should be about 7V above chassis. If it is much above this then switch off quick and replace the capacitor feeding the grid. Touching the volume control...
  17. duke37

    RF circuit , mixer help

    My word, that is complicated. What is the frequency you are using 1μF seems a lot for radio frequency? M5 seems to do nothing, it is turned hard on. Using fets (M1 and M2) in the mixer means that you will need a large voltage to turn then on and off, do you have this? There is no indication of...
  18. duke37

    Measuring current using current transformer ring type

    If the rectifier comes before the burden resistor, it will affect the measured current by adding 24mV plus 20mΩ (with a 1Ω resistor) in the supply. There will be no 1.2V drop in the measured voltage. This is used as a current transformer, not a voltage transformer. Any rectifier will give a non...
  19. duke37

    Measuring current using current transformer ring type

    I do not follow all the aswers here. I would use a bridge rectifier feeding the burden resistor to give a floating rectified output that could be connected to the computer. A capacitor may be necessary if the computer cannot log fast enough. The transformer has a ratio of 1:50 so the diode...
  20. duke37

    control 16 electromagnets

    Welcome to the forum. You need to define what you want better. Are they all going to be switched together or are they to run in a sequence. What is very rapidly? An elecromagnet is inductive and switching it rapidly is difficult. What will be the method of deciding what should be done?
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