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  1. duke37

    tripp-lite pr-60 transformer issue

    Sounds as if there is a shorted turn. If the transformer is saturating, then reducing the voltage with a Variac will drop the power dramatically. What is the transformer specification, does the supply comply? 110V transformer, 120V supply?
  2. duke37

    Cells with different voltage in parallel????

    Do not do it, the 5V battery will charge the 4V battery and perhaps melt the connecting wire. Where do you get a 4V or 5V battery? Is this describing batteries past their best.
  3. duke37

    Server Move

    I have just had a notification of an alert (top right), when ticked it put me on to a different thread. I used to get an e-mail alert. These have not come through in the last month or two, Not that I am worried.
  4. duke37

    Help with fence charger schematic

    5J is quite a powerful fencer charger. The energy in a capacitor is C*V^2/2 For 100V capacitor need 1mF = 1000μF For 500V capacitor need 40μF The capacitors are often special pulse types which can stand the large current when discharged. Electrolytic capacitors are not used. The output voltage...
  5. duke37

    3W LED dimmer

    A FET is a field effect transistor, they are very good for switches since they can have a very low resistance when turned on so often do not need a heat sink. The common ones need 8 or 10V on the gate to switch them on fully. Logic level FETs are designed for lower level gate voltages but...
  6. duke37

    3W LED dimmer

    Pulse width modulation (PWM) is the way to go. The classic 555 oscillator will do this and can be controlled with a potentiometer from near 0% to near 100%. It will need a power transistor to switch the 4.2A. The best type for this is a FET but it is doubtful if you have enough voltage to turn...
  7. duke37

    Energy Lost Due To Friction

    My method was to answer the question directly. The friction or angle of dangle are not needed. It is necessary to know the final velocity in any method to know the energy loss. I gave a way of estimating this from the time of flight. Why complicate things? How do you measure the loss of...
  8. duke37

    Energy Lost Due To Friction

    The thread is getting a bit long with several side issues, it might be better to start another one. Read through this thread and tell us what problem you have. Starting energy is the potential energy. Finish energy is the kinetic energy, estimated from the final speed. Energy lost is the...
  9. duke37

    Snap-on YA-205 welder, Century welder Solar welder wire won't feed

    Congratulations on the repair, glad to know it works. What needed to be replaced? I imagine that welder repair is not the most common thing to do and without a circuit diagram attached, it needs some enthusiasm to research the circuit. I have a welder to sort out here, it has a switch mode...
  10. duke37

    How to convert hight voltage ac into dc?

    What something else is there? Normally you would use a bridge rectifier, this puts diodes in series to aid high voltage capability and keeps DC out of the supply.
  11. duke37

    Finding a replacement MOSFET

    Digikey give an alternative P-channel fet which should do. The voltage should be greater. The current should be greater. The gate voltage tolerance should be adequate. The power capability should be greater. Why did the original burn out?
  12. duke37

    Is this circuit fit for purpose if used on a 12vdc pump?

    One diode is NV-1S3210 and the other is NV-1N3210R so they are of opposite polarity. The symbol we see may not be an indication of polarity and it looks as if the lower picture is a mirror image. Did Kris reverse the image to show the physical connections?
  13. duke37

    Rotary Tool Power Cord Resistors

    I agree with Minder but you can confirm that it is not a resistor by comparing with the good one. The chokes are used to reduce noise sent into the mains from the commutator intermittent contact.
  14. duke37

    Electrolytic capacitor questions (reversed polarity)

    The series resistor can be set by getting the same brightness as a led fed with 20mA. Some time back, I calculated the average current from the pulse of current, this involved calculus, last used 65 years ago. I am not doing it again, it would be quicker and easier to use LTSPICE.
  15. duke37

    Meaning of some german words on the front of a radio

    U1 to U5 are preset frequencies, probably set by permeability tuning.
  16. duke37

    1970 Delco Radio Repair - audio distorted

    If the power supply has a large ripple, then a capacitor is faulty. Look at the output waveform and see if it clips at high volumes. You will not get more output voltage than the PSU voltage. I think that more output could be obtained with a lower impedance speaker.
  17. duke37

    Should i short the chopper transistor for a ac adapter?

    You will need a lot of current and a lot of energy. Use the PSU to charge a colosal capacitor through a resistance and discharge it through the paper clip.
  18. duke37

    Electrolytic capacitor questions (reversed polarity)

    Or use two LEDs in inverse parallel if they will fit.
  19. duke37

    Help with fence charger schematic

    I have repaired several electric fence chargers, from the electromechanical type to mains driven simple high voltage transformer - frightening. The lightening damage may be restricted to a few components. I have never seen a faulty output transformer.. I saw no more damaged chargers when an...
  20. duke37

    What is making a squealing noise on this plug in?

    It may be a SMPS with Q1 as the switching transistor. If D1 to D4 form a bridge rectifier connected to the mains, then it is a SMPS. Is it my imagination that the electrolytic capacitors have domed tops? Faulty caps could overload the transformer.
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