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  1. audioguru2

    Simple voltage regulator

    Kevin, you need to learn about negative feedback. Your simple voltage regulator has no voltage gain. Its voltage gain is a little less than 1. Its 200k resistor does almost nothing (it reduces the voltage gain from exactly 1 to a little less than 1). The opamp is pretty fast but the darlington...
  2. audioguru2

    New Power Supply II

    Hi Redwire, On the original and fixed version your diode D2 was a resistor with almost NO voltage drop. Now the D2 has a voltage drop that changes when the temperature changes then the output voltage changes when the temperature changes. Without a negative supply for the current control opamp...
  3. audioguru2

    Audio Crossover light controller circuit

    It is called a "color organ circuit". You want it to have three frequency bands. Look for the circuits in Google Images where you will find hundreds of them.
  4. audioguru2

    Frank Huges transistor tester

    When there is no transistor connected and the switches are set to "Tr" then the CD4093 IC must have plenty of output current or the LED load stops it from oscillating. But with a 9V supply two paralleled gates of a CD4093 have a minimum output current that is too low to work in this circuit so...
  5. audioguru2

    New Power Supply II

    I turned off the video because I could not understand the very strong Engrish accent combined with the echoes in the room he is in. I think in part 1 he mentioned a lousy old LM358 opamp (it has poor high frequency response). One of the comments at the end of the video mentions poor transient...
  6. audioguru2

    New Power Supply II

    Your circuit has Q1 with high voltage gain and a phase shift from R15. You also have Q2 with high voltage gain and phase shift from R13. Then you feedback the high gain and extra phase shifts to the inverting input of the opamp so it oscillates. The original circuit used only a single driver...
  7. audioguru2

    Frank Huges transistor tester

    The link works when it is not crammed together with "newbielink". This link works:  http://na7kr.us/in-circuit_transistor_tester.htm . I think the tester slowly destroys a transistor when it makes the base-emitter reverse biased higher than its 5V maximum allowed rating which causes the fragile...
  8. audioguru2

    New Power Supply II

    The new circuit oscillates because the output amplifier transistors provide too much voltage gain. The original circuit and all the improvements until recently had only one driver transistor as an emitter follower with a voltage gain of only 1 like a piece of wire. Your new circuit has Q1 and Q2...
  9. audioguru2

    Current monitor/sensor

    Your camera is horrible. Why don't you sketch the schematic using Microsoft Paint program or another program? Your opamp has no power supply so it will not work. If it has only a single positive supply and ground then it must have inputs that have a common-mode voltage range that includes...
  10. audioguru2

    0-30V Stabilized Power Supply

    Good point. The current regulating opamp has its negative supply pin at the input of the 0.47 ohms sense resistor and the voltage regulating amplifier has its negative supply pin at the output of the current sense resistor which is 1.41V higher than the current regulator negative pin when the...
  11. audioguru2

    0-30V Stabilized Power Supply

    The negative supply is needed for the current regulating opamp to cause the output voltage to drop to zero when the current into a short circuited output exceeds the setting of the current-setting pot. Without the negative supply then the output of the current regulator opamp cannot cause the...
  12. audioguru2

    Potentiometer

    I have never seen a bad ALPS pot and have never ordered one. If the code had an "A" in it then it would have an Audio logarithmic taper. It has an "M" so it is a linear pot.
  13. audioguru2

    Variable PSU stability problem

    Without using thermal compound, the transistors are in one city and the heatsink is in another city. Then the heatsink will not be very effective. If the value for the emitter resistors is too low or the resistors are missing then one transistor will probably heat more than the other.
  14. audioguru2

    Variable PSU stability problem

    The 2SC5200 power transistors in a plastic case are much better than 2N3055 transistors in a TO-3 metal case. They should transfer more heat to the heatsink than the 2N3055 transistors. The heatsinks in your photos are tiny so no wonder the output transistors get hot. I do not know if you use...
  15. audioguru2

    Variable PSU stability problem

    you reduced the values of the resistors so that the low supply voltage for your voltage amplifier opamp does not cause poor voltage regulation. then if the output transistors are a little different then one will conduct much more current than the other and get too hot. Also the input offset...
  16. audioguru2

    0-30V Stabilized Power Supply

    It is very confusing when each new schematic has different parts designation numbers. Your new D10 has backwards polarity then the current regulation will not work. When the new U1 detects over-current then its output goes low enough to pull down the voltage feeding the voltage amplifier opamp...
  17. audioguru2

    Variable PSU stability problem

    The BZX55 zener diodes have their voltage spec'd when their current is only 5mA. Then the 6.2V zener diode has a power of only 5mA x 6.2V= 31mW, not anywhere near its maximum of 500mW. The 3.3V zener diode has a power of 16.5mW which is also nowhere near 500mW. Why don't you look at the...
  18. audioguru2

    Variable PSU stability problem

    Your project has poor voltage regulation when its voltage and current are high because the voltage regulating opamp has a low supply voltage of only 33V. Its maximum output is about 31.5V if you are lucky, the base-emitter voltage of the BD139 could be 1V and the Vbe of the output transistors...
  19. audioguru2

    I have a problem form Amplifier voltage divide

    Liquibyte, You have the transistor shorted with a wire from its collector to its emitter instead of a 10M voltmeter.
  20. audioguru2

    I have a problem form Amplifier voltage divide

    I do not know why so many calculations were made for the very simple circuit, most of the calculations are not needed to simply find the RMS power in the 5K ohms load. I simulated the circuit with LTspiceIV and it shows an output power of 9.0uW in the 5k ohms load.
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