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  1. duke37

    12 pulse rectifier output and filter circuit

    You have three bridge rectifiers with the outputs summed. The peak output voltage voltage will be the voltage between (1) and (10) times root 2. The filter is to smooth the output voltage and the component values will depend on the ripple which can be permitted. R1 is posibly to limit the...
  2. duke37

    Short/open circuit detector in wall

    I was asked to look at a friend's mother's house. The deep freeze in the garage was live (240V) and she was complaining of the shock when she opened the lid:). I tested it with my magic screwdriverand declined to touch the freezer. The poblem was that she had had the walls impregnated with...
  3. duke37

    Electrical Conductivity in Tap Water

    Some of each I would think, if you use two close plates, the fringe effects would be minimal.
  4. duke37

    AM demodulation and DC offset

    1. Yes 2. It does not. Post a copy of the circuit you are talking about with the components labelled.
  5. duke37

    Help with slowing down and reducing the noise on a shaded pole 230VAC fan motor

    I suggested a 1μF capacitor in #11. Nice to know my guess was reasonable. I also suggested that the switch could operate in the reverse direction. This is due to the supply to the motor being changed from constant voltage to constant current, defined by the capacitor. With the voltage supply...
  6. duke37

    Making Lead-Acid Style Batteries (With Alum / Epsom Salt)

    Just a couple of points. 1 I do not think that distilled/deionised water is necessary unless the other components are also pure. 2. Lead acid batteries have grid electrodes stuffed with lead paste. This has a much greater surface area then a flat lead sheet and so a much greater capacity and...
  7. duke37

    NPN PNP coupling capacitor

    What is the pupose of the circuit? It looks to me to be a RF amplifier with Q! setting the current through Q2. The capacitors are to bypass RF current so to smooth the supply. What are the component values?
  8. duke37

    AM demodulation and DC offset

    The RF bypass capacitor is in parallel with the signal to pass the RF to ground. The DC blocking capacitor is in series with the signal line.
  9. duke37

    12v Turn signal and running lights?

    If the lights are in the same position you do not know what the signal is unless the change in brightness is seen. Lights for different purposes should be in different positions. In the UK any change from standard must be notified to the insurance company which may not approve.
  10. duke37

    Making Lead-Acid Style Batteries (With Alum / Epsom Salt)

    Distilled water may be difficult to find but de-ionised water which is used in lead-acid batteries should be readily available at any garage. Have you determined the chemical reactions in the battery. Epsom salt is magnesium sulphate, how is this used to produce lead sulphate? Alum is a broad...
  11. duke37

    Hep needed to ID vintage tube

    Here is some data for rectifiers."Electronic Designers' Handbook" Landee, Davis, Albrecht. The scale on the left is rectifier peak resistance.
  12. duke37

    Hep needed to ID vintage tube

    There are lots of double rectifiers on an IO base 5U4, 5V4, 5Y3, 5Z4, GZ32, GZ33, GZ34, 5R4(GY), AZ31, U183, U50, U52, U54, EZ35, U147 etc. Some of them are directly heated and some indirectly heated. What is the heater voltage supply? The 5U4 or 5R4 are perhaps the most likely, both 5V...
  13. duke37

    How to connect a newer Shaded Pole Motor in my oven?

    And it does not matter which is the phase and which is the neutral. The motor metalwork should be ground or earth, this will be done elsewhere.
  14. duke37

    Help with slowing down and reducing the noise on a shaded pole 230VAC fan motor

    That is right. If the motor takes very little current, then the capacitor will drop very little voltage. If the motor takes a lot of current, then the capacitance will drop a lot of voltage. You have no alternative to trying a capacitor and seeing its effect. Previously I suggested 1μF, this...
  15. duke37

    FM fading

    @davenn The idea of the short is that the overall length of the aerial is half a wavelength and the short is placed where the line is resonant, taking into account the velocity factor. The value I have for Vf is 0.85, this is presumably for the solid plasic type, the ladder line will have a...
  16. duke37

    FM fading

    This is just a folded dipole, the short is due to to the velocity factor of the ribbon cable
  17. duke37

    1980 Soviet Radio Cassette amplifier problem.

    You loaded five snippets of sound a long way back. I only listened to two of them. The first one was the FM radio which I believe does not receive the broadcasts in Romania so that the radio is responing to spurious responses. If the deviation is extra large due to multiplication, this will...
  18. duke37

    Help with slowing down and reducing the noise on a shaded pole 230VAC fan motor

    The capacitor should be installed in series with the supply. The switch will still affect the speed but may work in reverse since the motor will be fed with a current source rather than a voltage source. A 400V capacitor may well work but I would go to 600V or even 1000V. Try 1μF and then add...
  19. duke37

    Help with slowing down and reducing the noise on a shaded pole 230VAC fan motor

    I have seen many shaded pole motors, non of them synchronous. I doubt if the motor shown could be made to click into synchronism with the large inertia of the fan. Also it does not need to be synchronous. The book (remember them?) "Alternating current machines" by M.G.Say has a large section on...
  20. duke37

    Help with slowing down and reducing the noise on a shaded pole 230VAC fan motor

    A shaded pole motor is not a synchronous motor, it will run slower than a synchronous motor would. The shaded pole motors are very inefficient and so produce a lot of heat. This is not a problem if they are driving a fan but it may be a problem if running slow.
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