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audioguru last won the day on March 11

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  1. 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 work but I do not think the maximum output voltage will be 30V, probably only 26VDC at 2A with lots of ripple. I wonder which circuit came first?
  2. 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. Measure the output voltage of the L298 that feeds the motor. If it drops lower and lower then also measure the input voltage of the L298 to see if it drops when the motor is slowing down. A Lithium rechargeable battery quickly becomes ruined if its voltage becomes less than about 3V per cell. my airplanes pulse the motor power as a warning to me that the voltage is becoming low then the motor stops but allows the steering servos to control the glide.
  3. Maybe your battery is not fully charged. Measure its voltage while the motors are running.
  4. Yes, the pots short circuit the input signals when turned down because they are shown wired backwards, instead of wired like volume controls.
  5. Sorry, I do not have time to modify this power supply for you.
  6. 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 should be used and the value of the resistor in series with the voltage calibration trimmer must be increased to set the maximum output to +15V.
  7. I think this old circuit should be kissed goodbye and be buried.
  8. audioguru

    LED panel .

    I cannot see which connects to what. Can you provide a schematic?
  9. 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 power is turned off then the resistors that feed the transistor need to be recalculated for the reduced voltage. I have used perforated stripboard for many projects including very complicated ones. The copper strips are cut to length with a drill-bit and become almost half the wiring of a pcb. The parts and a few short jumper wires become the remainder of the wiring. Only one wire is in each hole so changing a part is easy like on a pcb.
  10. 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???
  11. If the battery is good then it should power the circuit for a few hours when it is fully charged.
  12. 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 supply voltage are too low. I removed Q1 and somebody else later added it back in wrongly.
  13. 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 that has a high current. Then the battery is drained in a few hours. You learn by reading the datasheets and selecting parts that work together, not by having errors and more errors.
  14. 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 output current of only 0.35A if it has a huge heatsink. If it has a positive supply of +36V and a negative supply of -6V and its output voltage is set low then its maximum allowed output current is 2.5A if it has a huge heatsink. If it has the +36V, -6V supply and its output is set to +26V then its max allowed output current will be 7.5A if it has a huge heatsink.
  15. 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.
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