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0-30 Vdc Stabilized Power Supply


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Ok People I fixed it :D

So take this as a tip:
IF IT varies the voltage from 23v to 35v ONLY, you got the Emitter and Collector of the 2N3055 Mixed UP lol..

Cheers!! when I arrive home I will post some pictures if the administrator lets me (until I arrive home I hope the administrator will already have posted if I can post pics or not)


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Good. I'm glad that you spotted and fixed your problem.
So the 2N3055's emitter-base junction was avalanching like a zener diode, in series with the base-collector junction. No matter what voltage the output of U2 was providing, the output could not follow it down.

Now you can remove those fuses which reduce the supply's performance:
1) Remove the fuse at the transformer's secondary, since its resistance limits the huge momentary current through the rectifiers when they charge C1, when the supply is loaded.
2) Remove the output fuse, since its resistance spoils the supply's regulation, when the supply is loaded. This supply has an adjustable current-limit so the fuse is not necessary.

Xenobius, could you please measure the voltage across R1/C1 without any load, and again set to 30V with a 3A load?

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And one more substitution please: 2N2219

I can't seem to locate these in a form easily attachable to a heat sink. Can someone suggest another model(s) suitable for this circuit that would be easier to find in a "heat sink form" such as TO-220?

Thanks again (for the umteenth time!)

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Hehe thanks buddy for the compliments :D and sorry for the 50w resistor :p because I don't have one.

Here is another picture of it so even the people who are going to build it will have an idea of the layout :) (sorry for the dirt on the table but I was just drilling a PCB lol)


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I'm aware that the filter cap is recommended to be much larger uF wise but I'm wondering about the voltage rating. The original part list called for a 50V cap. I may have found some large-enough, 250V caps. Would using caps with much higher voltage ratings do anything good or bad to this power supply? Should they perform as well as the same size cap rated at 50V? There must be some kind of trade off. Perhaps physical size or cost?

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Hi! ... i'm new on this forum so i have some maybe allreday answered questions... sorry ;)

i'm wondering if someone has made a 5Amp modification and use the LM338 insted of LM317? is there a new PCB for that or something? Tell me what u changed...

I'm also thinking to do a dual power supply. that's two adjustable power sources. Can I build two PCB's and then use transformer whit "double secondary connectors".. i hope u know what I mean... and use it like that whit no further modification...

Thank you!

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Greetings, and welcome to our community.
We have discussed this project and have discovered some problems. We have another post that discusses how correct the problems and to increase its output to 5A. I have recently recommended changes that should allow this. There is a revised PCB layout there for my changes.The other post is here:

The circuit doesn't use a LM317 nor LM338 because they would not easily allow the circuit to do important functions:
1) Automatic change between voltage and current regulation.
2) 5A output at low output voltage. The LM317 and LM338 automatically fold-back their current limiting to protect themselves for their Safe Operating Area. The LM317 is guaranteed to give only 75mA, and the LM338 doesn't even have a guarantee, but is expected to give no more than 1A.
3) Voltage regulation down to 0V, and current regulation down to 2mA.

You have a good idea for a dual supply. With 2 separate transformer windings, the circuits will be completely independant.

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