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  1. audioguru2

    parallel bridge rectifiers

    Why not use a proper real heatsink with some thermal grease? A real heatsink has many fins for a high surface area. Then the bridge rectifier can work at closed to its 50A rating.
  2. audioguru2

    0-30V Stabilized Power Supply

    The 10A darlington will have a voltage drop of about 2V at 3A which might be OK.
  3. audioguru2

    0-30V Stabilized Power Supply

    I have used very high power audio amplifiers and they do not limit the inrush current to the main filter capacitor. But they used torroid transformers that might not saturate like an ordinary power transformer. When the power switch is turned on then maybe the inrush current almost saturates...
  4. audioguru2

    0-30V Stabilized Power Supply

    The voltage drop of 180 ohms at 3A is 540V! If you use 1.8 ohms then its voltage drop at 3A is 5.4V which might prevent the output from reaching 30V. With 1.8 ohms then the size of the zener diode must be huge.
  5. audioguru2

    0-30V Stabilized Power Supply

    I guess you know the 180 ohm resistor reduces the maximum output current to almost zero for an output voltage of 30V. The maximum output current with an output of 5V is only about 150mA.
  6. audioguru2

    6V Ultra-Bright LED Chaser

    For anyone who has the same problem that I discovered and fixed. I designed this project almost 10 years ago. This problem occurred on two projects that were 8 and 9.5 years old. The first LED remained lit when it should be turned off and each blinked LED had a light trail behind it. The cause...
  7. audioguru2

    0-30V Stabilized Power Supply

    With a 30V power transformer that is 31V when the project has no load then the peak voltage is 43.8V and the bridge rectifier drops it to about 42.6V which is the positive supply for U2. Then what voltage will you use for a spike cutting zener diode? A 28V transformer will be 29V when the...
  8. audioguru2

    Dynamic Battery Analyzer

    Please provide dynamic details. The internal resistance rise of the battery as it runs down? The voltage drop at the output of the battery as it runs down? The temperature rise of the discharging battery? What else?
  9. audioguru2

    0-30V Stabilized Power Supply

    The circuit at diyfan.blogspot has some of the problems of the original circuit here plus one: 1) The new problem is that the datasheet for the TL081 shows that its negative supply should be a minimum of 4V so that its inputs work properly all the way down to ground. Then when you add the +33V...
  10. audioguru2

    0-30V Stabilized Power Supply

    The output of the project should go down to exactly 0V when it has 2.7K for a load and C7 is a film cap. Then the output of U2 will be about +1V (it can go down to at most 100mV).
  11. audioguru2

    0-30V Stabilized Power Supply

    The maximum input offset voltage of a TLE2141C is only 1.4mV so the input offset adjustment should change the output plus and minus 1.4mV or more. The minimum output voltage of the TLE2141C (when the output is saturated as low as it can go) is about +100mV. U2 has no negative feedback when the...
  12. audioguru2

    0-30V Stabilized Power Supply

    Why does Texas Instruments show the RV1 circuit we are using for nulling the input offset voltage of their TLE2141 opamp then? Please double-check your pcb that pin 4 of U2 and R10 both connect together and to the 0V of the main filter capacitor. If C7 is an electrolytic then its dielectric...
  13. audioguru2

    0-30V Stabilized Power Supply

    Certainly, But we are not using the low max supply voltage TL081 opamp that has the inversion problem. The opposite. An inductor does not producer an inrush current. Charging the main filter capacitors quickly produces the inrush. The inductance of a transformer slows the rise in current for...
  14. audioguru2

    0-30V Stabilized Power Supply

    Doesn't the linear regulator eliminate the voltage spikes caused by U1? Redwire said it did. Does the linear regulator produce less noise than the zener diode/U1 circuit? When the mains power is turned off then the 47uF filter capacitor C3 for the negative supply takes time to discharge. The...
  15. audioguru2

    0-30V Stabilized Power Supply

    Hi Liquibyte, On your measurements it looks like Q1 turns on a little too late to completely squash the voltage spike but it reduces it a little. Are we barking up the wrong tree?? (I haven't said that for about 50 years) Without Q1 the 'scope photo from Redwire shows 24MHz ringing when the...
  16. audioguru2

    0-30V Stabilized Power Supply

    I found Redwire's 'scope photos of the 24MHz output ringing at turnon and shutdown on page 141 on May29/2014. The output goes -30V then +30V back and forth many times. I cannot read the settings on his 'scope so I don't know how much delay occurs from when shutdown occurs to when the ringing...
  17. audioguru2

    0-30V Stabilized Power Supply

    I do not know how a meter can show a spike. It can show a good long pulse but not a short duration spike. Didn't Redwire discover and measure the spike with his 'scope? Where is the post?
  18. audioguru2

    0-30V Stabilized Power Supply

    Hi Liquibyte, Your Rev7 looks good. You have R13 as 10k but I calculated with 12k but it doesn't make much difference. Leave it as 10k. When Q1 shorts the output of U2 and the base of Q2 to ground then R15 and D10 will prevent the charge on C7 (and on an external load capacitor) from causing...
  19. audioguru2

    0-30V Stabilized Power Supply

    Hi Liquibyte, I am glad it is fixed. I didn't build this project so please can you show a 'scope photo of the output noise from U1 and a comparison to the output noise of a voltage regulator? I think the old zener diode is a noise source. Can you also show a 'scope photo of a comparision in...
  20. audioguru2

    0-30V Stabilized Power Supply

    Sorry, I made a mistake converting the original schematic to the fixed and improved one. You do not want the negative supply pin 4 of U2 to be negative -1.3V because then U2 will have its total supply voltage very close to its maximum rating of 44V (+42.6V plus -1.3V= 43.9V). U2 does not need a...
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