Power Supply 0-30V

[bohko]

Where did the long topic of stabilized power supply dissapear??? I can not access it!!.

TNX
bohko

[audioguru]

Where did the long topic of stabilized power supply dissapear??? I can not access it!!.

TNX
bohko

The long thread and other threads about fixing and improving the project disappeared when this site's data became corrupted.

Here are the latest schematic and parts list:

[dracu_n_dulap]

Where did the long topic of stabilized power supply dissapear??? I can not access it!!.

TNX
bohko

just the question i wanted to ask.

Where did the long topic of stabilized power supply dissapear??? I can not access it!!.

TNX
bohko

The long thread and other threads about fixing and improving the project disappeared when this site's data became corrupted.

Here are the latest schematic and parts list:

is the data recoverable?

[fikic]

Hello,

I have build this power supply long time ago, and it didn't work correct. U2 was overheating and output voltage of supply was just 25V. I have changed opamps with OPA455 and now works the same. I have checked every connection, every transistor and diode. Everything is correct. Can you please help me.
Now, I know you will say, there is a update of this project on forum and new partslist and all this. But my friend has build it with original schematics and parts list and it works well for him. Can you explain me that please ?

Sorry for my bad english

[audioguru]

The original project is a mess of errors. We fixed it but the thread is gone.
The fixed version uses a real BD139 power transistor to replace the tiny 2N2219 that was used as Q2 and a 28VAC or 30VAC transformer at 120VA to 129VA is used.
The main filter capacitor has a value that is much higher and the power ratings of many resistors were increased.

Opamp U2 should never get too hot unless Q2 or a power transistor is connected with its pins backwards.

I am busy now but I will post the new schematic and parts list again soon.

[door]

Hi,
Collected the Power Supply. I turned on does not work. Strongly heats U2. In what could be the problem? The output of U1 (6) with respect to point 4 (-) voltage of 27V. Is this correct?

[audioguru]

Hi,
Collected the Power Supply. I turned on does not work. Strongly heats U2. In what could be the problem? The output of U1 (6) with respect to point 4 (-) voltage of 27V. Is this correct?

The output voltage from U1 has nothing to do with the heat from U2.
The output voltage from U1 should be 11.2V which is the 5.6V reference from zener diode D8 multiplied by two by U1 since R5 and R6 make U1 have a gain of 2.

U2 heats too much when its output current is too high due to a wiring problem with the pins of Q2, Q4 or Q5.

[door]

The output voltage from U1 should be 11.2V which is the 5.6V reference from zener diode D8 multiplied by two by U1 since R5 and R6 make U1 have a gain of 2.

U2 heats too much when its output current is too high due to a wiring problem with the pins of Q2, Q4 or Q5.

Found an error at the output of U1 is now about 11V.
The scheme collected on TL081, transistors Q4, Q2 checked, replaced, still U2 heats, the power supply is not working at the output of 0,45 V. At shaper negative voltage must be much volts? I have a 0,7 V, is that right?
Sorry for my English

[audioguru]

Found an error at the output of U1 is now about 11V.

Good.
Zener diode D8 is a better voltage reference if you change R4 to 1k ohms.

still U2 heats, the power supply is not working at the output of 0,45 V. At shaper negative voltage must be much volts? I have a 0,7 V, is that right?

Your U2 is overheating because Q1 is turning on and is shorting the output of U2.
The negative supply is supposed to be -5.6V which will turn off Q1 if your transformer is only 24VAC.
Maybe you have zener diode D7 installed backwards.

[door]

audioguru , thank you very much! All earned. Was a simple mistake, capacitors C2 and C3 were short-circuited, the holes in the board was unnecessary, did not find and solder properly. Oh, how glad I am !!!!!!!!

[Angelina_Apr]

please post more info on the unit and how it was damaged and perhaps someone can help with your problem.
 Was the damage due to excessive voltage lightning...etc?
 Does it have a internal fuse?
 Is it a switching power supply?
More Info??

[d4rkzone]

I want to know what I need to do if I want 0 - 10 A output instead of the 0 - 3 A.

[audioguru]

You want 3.3 times the output current. Then when the output current is set to 10A and the output voltage is very low (shorted?) the power dissipation in the output transistors is 424W and they will melt.

[d4rkzone]

I just wanted to turn on a laptop which use aprox. 19.5 V and 3.42 A. Then if 10 A is too high what if I want 5 A?