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  1. audioguru2

    Restoring a Juliette Receiever

    An LED needs a series current-limiting resistor calculated for a certain current, usually 20mA or 25mA for an ordinary LED to be bright. You tested your LED with an old 9V battery that limited its current because it was nearly dead. The 9V source in the radio has burnt out and maybe also the LED...
  2. audioguru2

    Spammer who is selling illegal drugs

    Horray! The spamming druggie is gone. The spammer clogged the New Topics listing so I nearly went away, never to return. It has happened many times before and will probably happen many times again because this website doen't use the methods to ban SPAM like all the other electronics chat...
  3. audioguru2

    0-30V Stabilized Power Supply

    With the current-setting pot at minimum, a load of 12mA or more will cause current regulation. Maybe C7 leaks as much as 12mA or more because it is connected backwards or because it is defective? Opamp U3 is a TLE2141 with a max input offset voltage that is much too low to cause your problem...
  4. audioguru2

    0-30V Stabilized Power Supply

    Then your schematic is confusing like Redwire's since parts not on the pcb are not shown.
  5. audioguru2

    0-30V Stabilized Power Supply

    VR3 is in series with R18 and the current-setting pot so it sets the max current before the current-regulation reduces the output voltage. The max resistance of RV3 is 100k and it is in series with R18 which is 20k so their total is 120k ohms. The original project used a total of only 56k so its...
  6. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Forp, I am sorry to hear that your project blew up. I am retired so every day is a Saturday and I do whatever I want, whenever I want. I made many projects on Veroboard (stripboard) but I have never mounted all parts on the copper side like you did. Opamp U2 controls the output voltage...
  7. audioguru2

    0-30V Stabilized Power Supply

    Since your current regulator does not work then U3 or D9 are not working. Maybe D9 is open or is disconnected. Maybe you messed up the connections to the current-setting pot or VR3.
  8. audioguru2

    0-30V Stabilized Power Supply

    You missed the second output transistor, the emittrer resistors for both output transistors and the emitter resistor for the driver transistor.
  9. audioguru2

    0-30V Stabilized Power Supply

    Hi Lighty, Which opamps did you use? Did you use Redwire's schematic? It is very hard to read with most opamps shown upside-down, many diagonal lines and missing output transistors and adjustment pots. U2, Q2 and the output transistors are simply an amplifier of the 0V-11.2V from the voltage...
  10. audioguru2

    A novice question on batteries

    A battery is charged with current, not voltage. But of course the voltage must be high enough. If you don't limit the charging current then the battery might melt or blow up. Nobody makes a deadly Ni-Cad 9V battery anymore. A 9V Ni-MH rechargeable battery is made as a six cells 7.2V/150mAh one...
  11. audioguru2

    Ni-Cad Battery Reconditioner Circuit

    Ni-Cads are old. Ni-MH are new and are better. Li-Po battery cells are the best. A Ni-cad battery cell developes crystals that short it. Then the total battery has less voltage but the same current as before. You can zap away the crystals but they come back soon. I have never heard about...
  12. audioguru2

    TA2024 Amplifier

    9W into 4 ohms is not much volume unless you live in a closet.
  13. audioguru2

    Spammer who is selling illegal drugs

    Could somebody please delete the many posts and ban the SPAMMING idiot who is recently selling illegal drugs here.
  14. audioguru2

    TA2024 Amplifier

    Look in Google. Tripath went bankrupt over 3 years ago. Their class-T amplifier ICs were low power and never worked very well. The TA2024 amplifier cannot drive a load as low as 2.6 ohms. Its output into 4 ohms is only 9W with very low distortion or 11W with higher clipping distortion. Your...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Yes. The Mickey Mouse contacts on a breadboard have poor contact so they have resistance. With a load of 250mA and a voltage change of 0.5V then the resistance is 0.5/0.25= 2 ohms. A soldered wire has a resistance of 0.001 ohms or less.
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    It must be made on a pcb. The long connection wires and tracks on a breadboard are antennas that pickup mains hum (your 50Hz junk). The high capacitance between the wire ands tracks on a breadboard cause capacitive coupling which causes ringing and oscillation (your high frequency stuff). The...
  17. audioguru2

    13.8V 20A power supply by Santa

    No. Your transformer has a max output of 17V to 18V at 400VA. Then its max output current is 400/17V= 23.5A.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    The current regulation works by U3 comparing the voltage across R7 caused by the load's current with the voltage across the current-setting pot and its series resistor. When the current in the load exceeds the set amount then the output of U3 goes low which turns on the LED and reduces the...
  19. audioguru2

    TIP142 Stepper motor driver

    When any of your darlington transistors turns on, it is a dead short from the +24V supply to ground. The coils in your motor are never powered because both of their wires are always at +24V. All outputs of your darlington transistors are shorted together.
  20. audioguru2

    0-30 Vdc Stabilized Power Supply

    The original project has no calibration so its max output current is too high at about 4.1A. Then if the output is shorted the 2N3055 transistor must dissipate 131W which will cause it to overheat even if its heatsink is huge. Maybe the current regulator circuit in your project does not work so...
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