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  1. duke37

    ac voltage regulator

    You are only dealing with an amp or two. You can get 5A diodes cheaply. The zener will not get any hotter, when it passes current. it turns on the SCR so drops the voltage to a volt or so. The zener will dissipate very little. An SCR normally has a resistor gate to ground to stop false turn on...
  2. duke37

    ac voltage regulator

    You need to stabilise voltage not current. AC has a varying voltage, the zener will pass current when there is 6.2V across it and short the supply. Thus the peaks are trimmed as is also the rest of the cycle. You will need to raise the zener voltage. I am not sure of the effect of only...
  3. duke37

    RLC circuit question

    In the equation for Z, you have an R^2 term, the reactance should also have a ^2 term.
  4. duke37

    RLC circuit question

    Subtract these two figures to get the nett reactance. Add the resistance in the correct way (not simple) to get the total impedance.
  5. duke37

    Drain-Source Breakdown Voltage

    I do not think that a positive volage is ever specified. It is just a voltage without polarity. If a negative voltage is specified this is just to underline that the device is p-channel
  6. duke37

    MOSFET Resistance Problem

    The mosfet looks to be OK but may not stay that way. Wih no voltage between the gate and emitter, the mosfet will be off so measres infinity resistance. There is however a diode inside the mosfet so which will pass current with the appropriate polarity. The 5.88M you measure is probably 0.588V...
  7. duke37

    Need help with Heathkit io-10 o-scope repair

    There are four posibilities. 1. The transformer is faulty. With the rectifier removed and the set unpowered, test the continuity of both sides of the HT winding. If one side is open circuit, this could saturate the transformer core giving excess input current. 2. The 6X4 rectifier is faulty. A...
  8. duke37

    How does diode dissipate energy?

    The electrons lose energy when they jump down an energy level, some give out light when they do this. I never did understand it and gave up when the concept of reciprocal space was introduced.
  9. duke37

    oscillator circuit

    The quick answer is that I do not know ! T1 is the oscillator which is an amplifier with a frequency selective component in the positive feedback. In this case the selection is done by the crystal. However there are two feedback paths, one through the crystal and one through C2 to the emitter...
  10. duke37

    Need help determining components for a circuit.

    Transistor 2SA1015 50V 150MA, this is a bit unlikely, it is probably 150mA Gain about 100. According to my book it is a silicon dvice and would need different biassing. Perhaps my book is wrong. 2SA numbers under 480 are shown as germanium Quite an acceptable price. Diode 1N34 I have not...
  11. duke37

    Electric fencer from a 12V battery

    I see that you have used the SCR to short the HT line in one case and to switch in series with the transformer in another case. Do you see any difference in performance? Perhaps the optocoupler cannot pull pin 1 of the UC3843 low enough?
  12. duke37

    Need help with Heathkit io-10 o-scope repair

    Does the fuse blow when the rectifiers are removed? If no, then the reservoir capacitors could be faulty. If yes, then it could be the transformer. To test the transformer properly, then all the secondaries should be disconnected. Rather than replace the fuse over and over again, you could use...
  13. duke37

    Electric fencer from a 12V battery

    Congratulations on getting a working circuit. Two points You appear to alter the pulse frequency - that is fine, but also the SCR trigger duration,. Why? You should be able to inhibit the 300V invertor so could eliminate the IRF740. Would you then need any optical isolator?
  14. duke37

    How can I set a frequency in a Wien bridge oscillator

    In one simulator that I have used, (forget which one), the oscillator had to be given a kick to start it. You need a gain of three, less than this and nothing happens. More than this and you get distortion hence Dave's suggestion of gain control with a variable component depending on signal...
  15. duke37

    How can I set a frequency in a Wien bridge oscillator

    You have given the equation 2*pi*f = 1/(C2.R2) So f = 1/(2*pi*C2*R2) Chose convenient capacitors and calculate the resistors. Resistors between 10k and 100k would be best.
  16. duke37

    How can I set a frequency in a Wien bridge oscillator

    C1, C2 and R3, R4 set the frequency. To vary the frequency two components need to be altered. Normally this is done with a dual potentiometer varying R3 and R4 together.
  17. duke37

    (Woo Woo) Efficient HHO Cell

    To get liquid hydrogen it needs to be below 33K, a little bit chilly. High pressure on its own will not do it. If hydrogen is to be produced, it should be used in a fuel cell which is better than an inefficient infernal combustion engine. As has been pointed out before, ther is no point in...
  18. duke37

    (Woo Woo) Efficient HHO Cell

    It would be helpful if some numbers were used to back up your proposals. A petrol engine has an efficiency of about 30%, a diesel about 40% and very big diesels a little more. These numbers are limited by heat loss and the efficiency of the heat cycle. I can believe that it may be possible to...
  19. duke37

    Check my wiring scheme please

    A heater is just a resistor which will get hot irrespective of the current direction. Your heater may run on AC where the dirction changes many times a second.
  20. duke37

    Check my wiring scheme please

    Thermocouple wires are not the same, the thermocouple produces a DC voltage and this must be connected the right way round unless you wish to control down to absolute zero ! All thermocouples I have seen either have coloured wires or a coaxial connector.
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