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  1. duke37

    5KHz Regulated Supply

    Use a Wien bridge oscillator to drive a reasonably powerful audio amplifier. You have not said what frequency deviation, amplitude accuracy or distortion level you can tolerate.
  2. duke37

    Cheap Motion sensors , chinese I think

    To calculate parallel resistors, use a reverse polish calculator - there is no need to phew! 33 1/x 2 1/x + 1/x gives 1.89 I cannot get my head around the new arithmetic calculators.
  3. duke37

    Inter M Qd 4960 Amplifier Problem

    1. Eyes 2. A decent voltmeter, I prefer analog but most prefer digital. Maplin often do cheap digital meters for less than £5. 3. 2ft of wire. 4. Time. 5. A camera There are a couple of electronic shops in Chesterfield. I have used Bowood.
  4. duke37

    Transmitter circuit operation explanation

    I looked up the BF982 and I found it is a MOSFET. It has protection diodes across the gates which will act as oscillation limiters and provide AGC action so no additional diode is necessary.
  5. duke37

    Transmitter circuit operation explanation

    R6 100k holds the gate at around zero volts. Normally this would have a diode across it so that the gate would be biased negatively when the oscillator is working, giving a level control and reducing distortion.
  6. duke37

    Inter M Qd 4960 Amplifier Problem

    You have two amplifiers driven in anti-phase feeding a driver in a bass cabinet. 1. Look for signs of any physical damage. 2. Compare the voltages of the good and bad amp. see 3 3. Use each amp independantly to drive a speaker (with an output capacitor). 4. Get a circuit diagram and data on any...
  7. duke37

    Clap switch confusion!

    You have not said what is wrong.:rolleyes: If nothing works, then split the circuit between the chips and check the stages individually. Do you have enough voltage? 5V into the 4017 will give less than this out, check the data. There will be 0.6V lost in the transistor, you have not said what...
  8. duke37

    Confused by circuit. A to B and B to C implies A to C?

    Videos here sometimes work and sometimes do not. I abhor them, they wiggle around and have bad sound. Use pictures and text. You need a resistor in series with the leds. If A connects to B and B connects to C, then there is a connection between A and C.
  9. duke37

    Clap switch confusion!

    What is wrong? You need diodes across the relay coils to protect T2, T3 and T4 from induced voltages. Have you got it wired correctly I do not see R7, R8 and R9. Not that it matters. There seems to be many connections from T2,T3 and T4 to +5V. Are you putting too much current through the...
  10. duke37

    What questions should I ask when ordering a Rheostat from a Manufacturer ?

    Are you trying to set voltage or current? For voltage you will need a multitap transformer and a multiway switch. !000V at 10A = 10kW, quite a lump of a transformer. For current you will need some form of regulator, again 10kW will need a large cabinet with ventilation. A rheostat will be...
  11. duke37

    LED project, heat dissipation

    There are european standards for vehicle lighting. Many years ago Ford had poor lights which caused accidents, they had to change. If the standard lights are changed by a bodger, then the insurance will be invalid and a prison sentance is a possibility. Even changing the type of tyre (tire) can...
  12. duke37

    Huming sound in homemade bluetooth speaker

    Why do you use two amplifiers in series? You are amplifying the high frequency leak from the first amplifier. If you need more gain, then make a simple analog amplifier with two transistors or one operational amplifier. This will be much simpler than trying to filter out the high frequency...
  13. duke37

    Where can I learn how to design a transformer?

    Look up ludens transformer.
  14. duke37

    Huming sound in homemade bluetooth speaker

    It seems as if this is a class T amplifier which is a version of a class D amplifier. These use high frequency switches in the output stage instead of linear devices. To make the waveform you want, the switching varies in frequency or pulse width or both. The output is filtered to reduce the...
  15. duke37

    Fluorescent Lamp/Ballast/Starter Help

    That is to be expected. The starter has to open to get a high voltage pulse to ignite the tube. I suggested unplugging the starter to see if the light stays on. Be very careful.
  16. duke37

    Fluorescent Lamp/Ballast/Starter Help

    I have never played with one of these. You could try unplugging the starter and see if the light stays on. I do this with a flckering normal fluorescent light but we have 230V to drive it. It would be better to run it through an isolating transformer. Do not want to lose you.
  17. duke37

    Huming sound in homemade bluetooth speaker

    You will not be able to hear 200kHz (not 200KHZ). It has nothing to do with degrees Kelvin. Using a power amplifier as a preamp gives a large voltage and current gain which must be controlled with very careful ground connections. Why do you put the amplifiers in series? The buzz is probably...
  18. duke37

    Transmitter circuit operation explanation

    Chris, you will need to pedal quite hard to catch me up. Trevor
  19. duke37

    Transmitter circuit operation explanation

    R5 reverse biases the two variable capacitors so they do not pass current. The audio amplifier swings this bias up and down so varying the capacitance and thus the frequency. These are diodes optimised for capacity change but in my day we used standard rectifying diodes such as the BY100. Draw...
  20. duke37

    Transmitter circuit operation explanation

    Sorry, my mistake, should have said C4. Will have to get my eyes amplified.:rolleyes:
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