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  1. duke37

    New valve amp build

    I would suggest that you use a standard circuit especially if you are going into business. The required load impedance of the amplifier is determined by the load line and is given in valve data. The output impedance of the valves could be many times the load impedance and there is no point in...
  2. duke37

    New valve amp build

    The impedance of speakers vary wildly depending on the frequency and the box in which they are installed. Just use the value marked on them. Happy Christmas
  3. duke37

    Dimming inductive loads using SSR causes SSR to break

    A transformer needs to be driven with AC without a DC component or it can go into saturation and pass a very high current. I supplied my neigbour with a transformer to heat a wire to cut polystyrene. I put a 100W light bulb in series with the dimmer switch and transformer, this worked at the...
  4. duke37

    Amp

    If you had no voltage on pin 5, then there is a power supply fault. Show us the voltage on all the pins, relative to the tab.
  5. duke37

    Amp

    There will always be an earth pin. What tests did you do? Give us the details. If you change the type of chip, then you will need to re-design the circuit. Do you wish to do that?
  6. duke37

    How to increase voltage from 2v to 12v?

    Please give more information. Is the 2V just a signal or is it a power supply? Do you have 12V available to drive the relay? What current does the relay take?
  7. duke37

    Capacitors

    Read up the information on Wikipedia on electrolytic capacitors and anodising. There are subtle differences other than capacity, polarity and voltage which may need to be taken into account for fussy circuits.
  8. duke37

    New valve amp build

    375 V and 107mA will give 48W 800 v and 91mA will give 100W 600 V will therefore give about 70W. Load varies from 3500 to 11000 ohms so chose about 5000 ohms. You will need to set the bias, drive and load lines for your particular situation.
  9. duke37

    Capacitors

    Why ever should you need a polarised capacitor when you have a non polarised one? Why would you chose a car which can only go forwards? This is the same logic. Polarised capacitors (electrolytics) are much smaller than non polarised ones so they tend to be used for different puposes. A 1uF...
  10. duke37

    Wanted help with electronic generator govenor

    Nice job on the timing wheel. As I suggested earlier, perhaps the servo just uses the average voltage, if so, you do not need any pulse generating circuit. Take a servo and slowly increase the input voltage and note the effect. A DC motor could be used to open and close the throttle with...
  11. duke37

    Capacitors

    A capacitor has two 'plates' with a dielectric in between. If the dielectric is air, the capacity will be low. The capacitor can be connected either way round, it works just the same. If the air is replaced by a substance with a dielectric constant of greater than one, then the capacity will...
  12. duke37

    Buffer or pre-amp?

    I imagine the words mean what you want them to mean. My interpretation is that a buffer isolates the source from the load, possibly by having a high input impedance and a low output impedance. A preamp amplifies the signal, it may or may not have controls.
  13. duke37

    New valve amp build

    To get the peak voltage, multiply the RMS voltage by the square root of 2. 450 * 1.414 = 636 This needs to be fed into a moderate sized capacitor, a very large one will cause the current to flow on just the peaks of the voltage and this high current will cause overheating of the transformer...
  14. duke37

    Amp

    Lokking up the data from ST gives the following information. Counting from the RIGHT. 1. Audio input at half of supply voltage. 2. Feedback, same as output voltage. 3 and TAB. Ground 4. Output, should be half supply voltage. 5. Supply Measure the voltages with a sensitive meter...
  15. duke37

    How many bloody cells???

    A lead/acid battery will have 2V/cell so a 12V battery will have 6 cells. Car 12V batteries are charged between 13.8 and 14.4 volts. With a sealed lead/acid battery which cannot have water added, I would charge to 14V.
  16. duke37

    PCB & environmental problems

    Silicon is no good since it is a solid. Silicone sealers come in two types, one type gives off acetic acid which will promote corrosion. Wax will give good protection at room temperature and the acrylic up to 50C. Epoxies may be able to withstand slightly over 100C. All metal surfaces...
  17. duke37

    Capacitors

    The main difference is size (and cost). Electrolytic capacitors can be used when the voltage does not reverse and frequencies are low to medium. A Farad is a measure of capacity and 1F will change voltage at the rate of 1V/second when fed with 1A.
  18. duke37

    New valve amp build

    Chris is strictly correct to get maximum power but this is not what you want. If you go for maximum power, you will likely burn out the valves. For an audio amplifier, there is an optimum load line, which approximates to a line from minimum votage and maximum current to maximum voltage and...
  19. duke37

    New valve amp build

    The 450V-0-450V transformer will give you 636V when rectified. This will be above the normal electrolytic capacitor voltage, you will need two in series with balancing resistors. A choke filter should be added and then large capacitors to cater for the current pulses demanded by the class B...
  20. duke37

    Wiring help

    I am not sure what you want to do but setting enable high will inhibit the counter. You could also intercept the reset line.
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