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  1. duke37

    12V - 350V 200mA converter for motorcycle CDI

    Many years ago, inverters were made to generate the sort of voltage and power that you desire. These used push-pull circuits which were self oscillating. When the transformer saturated, the output would switch. If you use a separate oscillator it must run fast enough to stop saturation. I have...
  2. duke37

    Refrigerator Not cooling

    If the compressor is running but not working it is possible that the system has leaked and gas has been lost. Most refrigerators have a sealed system but loss of gas is common in air conditioning systems in cars where the drive is through a rotating shaft.
  3. duke37

    Silicon Diode problem

    You obviously know that D1 drops 0.7V when conducting. Quite correct. So what voltage will D2 have across it when conducting?
  4. duke37

    Silicon Diode problem

    What is the voltage across R1?
  5. duke37

    Small PCB From Power Supply Keeps Blowing 3A Fuse

    Has the main electrolytic got a domed top. If so it is probably dead. You could take it out and see if the fuse blows.
  6. duke37

    voltage comparator

    You could add a PNP transistor to the output, base to base, emitter to emitter and collector to ground. This would protect each transistor and discharge the capacitor when the control is turned down. A fairly fat transistor would be required but a heat sink should not be necessary unless you...
  7. duke37

    AC adapters

    The peak voltage of an AC wave is 1.4 times the quoted voltage. So 110V AC has a peak of about 150V If the input is rectified this is what you get. Running the PSU at 100V means the input is underdone but it may work. Some switch mode power supplies have a wide range of permitted input...
  8. duke37

    voltage comparator

    Could the signal inversion be done in software so eliminating Q1? Changing the complicated circuit to a piece of wire seems quite neat.
  9. duke37

    24V 2A Variable Power Supply

    Yes, if a parallel diode is used, then both transistors need to be protected.
  10. duke37

    voltage comparator

    T3 inverts the signal so high input gives low output at pin 7. T4 and T5 do nothing except drop the impedance, this is not necessary. They can be removed. Most comparators need a pull up resistor (R15) but R16 pulls it down, which will win?
  11. duke37

    AC adapters

    A CFL contains an inverter which runs off rectified mains (>300V) and this circuit could be used on 100V to supply the 5V required. The circuit is simple and very small. Do you wish to do some development work?
  12. duke37

    AC adapters

    You need a buck converter, there are many around but mostly about 30V input. If you really want to do a lot of work, you could modify a computer power supply. These are capable of much more power than you need. My broadband is only slimband so searching is painful.
  13. duke37

    24V 2A Variable Power Supply

    Confirmed.
  14. duke37

    AC adapters

    If the adapter contains a normal transformer, defiantly NOT. If the adaptor is a switched mode power supply, perhaps.
  15. duke37

    24V 2A Variable Power Supply

    A rough calculation suggests that T2 could dissipate up to 70W. A BIG heat sink would be required for this. The added diode is there to protect the transistor, you do not want to pop off another. A 10k load on the output would drop the voltage quicker as you suggest. The time constant will be...
  16. duke37

    24V 2A Variable Power Supply

    You will need a much bigger heat sink if you are going to utilise the full capability of the circuit. T2 must not have a large negative voltage base/emitter. A higher output voltage than the base is not a good thing. Reducing C5 would allow the output to drop faster but I would not do this...
  17. duke37

    24V 2A Variable Power Supply

    You still havn't said what you mean by used. Was it driving an led at 2mA or charging a battery at 14V 5A? Measure the voltages on T2 and measure output current. Much more information is required.
  18. duke37

    24V 2A Variable Power Supply

    What do you mean by used? T2 should not get hot unless you have a considerable load current. Have you connected the output stage correctly? With 0V on the base of T1, the output should be 0V.
  19. duke37

    1979 sanyo receiver blowing fuses

    C901 is 0.01μF +100 -0%. In other words can be up to 0.02μF but not less than 0.01μF. Minus and to can often be confused. +/- 10% would almost certainly work. The value does not appear to be critical.
  20. duke37

    Dumb question re. simple inverter

    I have a book, remember them? COS/MOS B-series Devices Databook 1st edition by SGS-THOMPSON MICROELECTRONICS. They give details of the HCC4047B. I am sure you could find details on the web in a short time. I doubt if the frequency is very accurate which presumably is why a trimmer is included...
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