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  1. audioguru2

    Laptop Battery rebuild

    As a lithium rechargeable battery is used, its running time slowly becomes less and less. It needs to be replaced or rebuilt when its running time becomes too low for you. Nothing in the protection circuit should make a noise like you have so your protection circuit is probably faulty and...
  2. audioguru2

    0-30V Stabilized Power Supply

    I also recommend 12000uF. You need a total of 12000uF for low ripple. Use hundreds of small capacitors in parallel if you want and if your enclosure has space for them. If the voltage rating on the capacitor is too low then it will fail.
  3. audioguru2

    More and more SPAMMERS

    Could somebody please get rid of all the new SPAMMERS who are trying to sell cheap Chinese shoes here? Why do they come here? Are they wierd people or are they robots?
  4. audioguru2

    0-30V Stabilized Power Supply

    A 28V/119VA transformer will operate at its max allowed temperature when the power supply has a 3A load. But a 28V/200VA transformer will be pretty warm, not hot when the power supply has a 3A load. Of course the 200VA transformer is heavier and costs more than a 119VA one.
  5. audioguru2

    0-30 Vdc Stabilized Power Supply

    Good. you fixed it. Doors and windows open and close. But transistors turn on and turn off. The output transistors are not fully turned on in this circuit because the opamp U2 cannot drive its output voltage high enough. U2, Q2 and the output transistors have a combined voltage loss of as high...
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    U3 is supposed to have a DC voltage gain of typically 220000. Maybe it is bad or C4 is leaky. Maybe U3 is a counterfeit IC that cannot reduce its output voltage as low and and does not have inputs that work at such a low voltage as a real TLE2141 opamp. When U3 is not regulating the current...
  7. audioguru2

    0-30V Stabilized Power Supply

    The max output voltage will increase a little when the current is lower. But the output suddenly will be full of ripple and will not be regulated near the max output voltage.
  8. audioguru2

    0-30V Stabilized Power Supply

    with a 24V/102VA transformer, the max output of this project at 3A is about 24VDC to 25VDC.
  9. audioguru2

    0-30V Stabilized Power Supply

    The voltage from your transformer is far too high for this project. The transformer is marked "98VA". A transformer does not consume power (Watts), instead it passes power (VA) so its power is rated in VA, not in Watts. Your transformer does not show its rated voltage. 24/91 are just...
  10. audioguru2

    0-30V Stabilized Power Supply

    31.5VAC has a peak of 44.5V. The rectifier bridge and main filter capacitor will produce an unregulated positive supply of 43V for opamps U1 and u2 which is close to their max allowed supply of 44V. If the mains voltage is a little higher then the opamps might fail. A 28VAC (at full load)...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Kankki, Your schematic is normal so I don't see anything wrong with the current regulation. When the output current tries to exceed the setting of the current pot then the circuit should reduce its output voltage so that the current stays at the setting. You probably have an error or short...
  12. audioguru2

    0-30V Stabilized Power Supply

    The collectors of the two output transistors are connected together so they can be directly bolted to the heatsink without transistor insulators but then the entire heatsink must be insulated from the metal chassis.
  13. audioguru2

    0-30V Stabilized Power Supply

    You are looking at the original project that is (was?) a kit in Greece. It has many errors that cause it to fail because the supply voltage for the opamps exceeds their max allowed supply voltage, the transformer and output transistor are overloaded and the old driver transistor is severely...
  14. audioguru2

    0-30 Vdc Stabilized Power Supply

    Opamp U2 drives transistor Q2 which drives transistors Q4 and Q5. When the output load current is 3A then the max base current into the combined Q4 and Q5 is 86mA. Then the max base current into Q2 is about 1.7mA. Then the max output current from opamp U2 is only 1.7mA which will barely make it...
  15. audioguru2

    Led display Digital Voltmeter question

    There are two versions of the old ICL7107 IC. The newer version ICL7107S has improved Stability. The LED display draws up to 224mA through the IC which heats it a lot and causes it to drift. It needs an additional -5V supply but you don't say how you produced it. The L7805 regulator must have...
  16. audioguru2

    Led display Digital Voltmeter question

    Has anybody made this very old project work properly? It will probably work properly if it is built according to the datasheet for the IC.
  17. audioguru2

    0-30V Stabilized Power Supply

    U2, Q2 and Q4 are an amplifier with a voltage gain determined by the values of R11 and R12. R11 is 27k and R12 is 56k so the voltage gain is 1+ (56k/27k)= 3.074. The trimpot reduces the gain to be low enough so that the max output voltage is 30.0V when the voltage pot is set to max and has 11.2V...
  18. audioguru2

    SPAMMERS

    SPAMMERs are obvious. They appear every day and their many posts completely fill the "Recent Topics" list so that we cannot see any real topics. Now they are trying to sell their cheap running shoes.
  19. audioguru2

    2-4.5VDC input to 5VDC 1 amp output Boost Converter - need help troubleshooting

    Your problem is the resistance of the contacts on the breadboard and all the too-long connecting wires. Use a compact pcb instead. The little AA Ni-MH cells might last 45 minutes providing 2.2A into the DC-DC converter that has a 1A output.
  20. audioguru2

    SPAMMERS

    Please get rid of all the SPAMMERS today. Can't we prevent a new SPAMMER from posting "millions" of times?
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