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  1. audioguru2

    LED panel .

    Can you provide a link to the ebay ad? Your schematic shows strings of 3 LEDs in series and a tiny resistor is also in series. Your pink and blue lines show that all the strings are in parallel. Since a white LED is about 3.2V to 3.6V  then the entire bunch of LEDs uses a 12V supply.
  2. audioguru2

    BMS Charger for 18650

    You have 12V, not plus 12V and minus 12V which is 24V. What you label as -12V is actually 0V. An ordinary older type of Lithium Ion cell is 4.20V when fully charged so your charger should have an output up to 12.6V, not 12.0V. The charger circuit should have wires connected between the series...
  3. audioguru2

    0-30 volt stailized power supply

    The circuit is the same as the old Greek kit here except a few part numbers are changed and the maximum output current is only 2A. It also has the problem of an overloaded transformer since with a 2ADC output the 25VAC input is 2.83A, not 2A. I ,saw some 741A opamps rated at 44V which might...
  4. audioguru2

    Rc car

    I have some Li-PO batteries for my RC airplanes that had hundreds of flight and had storage for a few winters. I can charge one and use it and it produces a problem like you have but it charges normally. The battery is worn out and cannot produce normal power continuously for a normal duration...
  5. audioguru2

    Rc car

    Maybe your battery is not fully charged. Measure its voltage while the motors are running.
  6. audioguru2

    Help interpreting Circuit schema please...

    Yes, the pots short circuit the input signals when turned down because they are shown wired backwards, instead of wired like volume controls.
  7. audioguru2

    0-30V Stabilized Power Supply

    Sorry, I do not have time to modify this power supply for you.
  8. audioguru2

    0-30V Stabilized Power Supply

    Sine you need a maximum output of only 15V and since most ordinary opamps have a maximum supply voltage of 36V then use an 18V transformer and the -5.6V negative supply as in the original project. The BD139 driver transistor and two 2N3055 output transistors in the latest version of this project...
  9. audioguru2

    0-30V Stabilized Power Supply

    I think this old circuit should be kissed goodbye and be buried.
  10. audioguru2

    LED panel .

    I cannot see which connects to what. Can you provide a schematic?
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original circuit should work fine up to 15V at 1A if you replace the old opamps with the newer higher voltage ones. You probably should recalculate the resistors that set the maximum voltage and current outputs. If the Chinese kit uses the transistor that shorts the opamp output when the...
  12. audioguru2

    Phone components

    There are a few completely different types of phones and you do not say which one. Landline phone, wireless phone and cell phone. Take one apart and look inside then count the components. Why??? 
  13. audioguru2

    automatic Solar Lamp

    If the battery is good then it should power the circuit for a few hours when it is fully charged.
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    When the negative supply collapses to 0V when the positive supply is still 37.8V then the current in both resistors in series is 37.8V/(12k + 160 ohms)= 3.1mA. If the base is +0.65V then the current in the 160 ohms needs to be 0.65V/160 ohms= 4.1mA so the 160 ohms resistor value and the negative...
  15. audioguru2

    automatic Solar Lamp

    The battery is powering the opamp and LED when the solar panel is dark. You did not say a part number for the opamp, Mosfet or driver so we do not know if they will work from only 3.2V to 4.2V. The 3W LED might use a current of 3W/4.2V= 0.7A and maybe your opamp is actually an audio power amp...
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    The OPA541 shows in its datasheet that if its positive supply is your 48VAC rectified to make +66VDC, its required negative supply is -6V and its output is 0V (shorted or set to a low voltage) then the output transistor in it has a voltage of 66V across it and figure 11 shows a max allowed...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Did you know that Chinese companies (ebay, Aliexpress, Banggood, Amazon and others) have copied the original defective Greek kit and used the wrong opamps and resistors that burn up? Their kits of the original project are very cheap. They use some Oriental transistors instead of the original ones.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original project used a 24VAC transformer and TL081 opamps that have a maximum allowed supply of 36V. Since the project was not able to produce 30VDC at 3A because the supply voltage was too low, I changed the transformer to 28VAC and changed the opamps to TLE2141 that have a maximum allowed...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    One 2N3055 transistor overheats in the original circuit that used a 24VAC transformer and produces 25VDC at 3A. Therefore I used higher voltage opamps, a 28V 4.2A transformer, a more modern driver transistor Q2 that can be cooled well and two 2N3055 transistors to share the heat on a very large...
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    Sorry, I did not see the 48VAC total voltage. The maximum allowed current from the 48V transformer is only 3.33A but for an output from the project of 3A DC, the transformer must produce 3 x 1.414= 4.2A, because the rectified 48V produces 66VDC at 3A which is 198VA. But the transformer is rated...
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