Hi friends, i bought a 0-30V 1.5A power supply which its voltage can be set with a potentiometer.
Then i removed a plug from an old toaster 
Then the polyester capasitor is blowned and with the house's fuse.
Can i use the circuit again If i change the capasitor ?
And how should i use that kind of power supply?
Just replace the capacitor? NO!
That power supply board is likely totally toasted. There is NOTHING on that board that indicates that is capable to taking anything but maybe 30V AC from a 220-30V transformer.
You didn't use a transformer... you fed the board 220V... so you exceeded the specifications for nearly every part on board. Throw the PCB away and learn from the experience.
That was a very dangerous thing to do, by the way.
The part you should have plugged your toaster wire into is below... and the output from the transformer would be attached to AC IN on the board.
A bit expensive experience 15$.
What should i have done? What was the purpose of this product?
The purpose of the PCB is to take a Stepdown transformer output and create a desktop (LAB) adjustable regulated power supply for projects. The use of a transformer was "implied".
Understood. I should have used that part between 220V and the PCB.
What is the exact name of it ?
220V to 30V transformer
Something like this: http://www.ebay.com/itm/Doorbell-type-Step-down-120-240V-to-8-16-32V-12W-Transformer-12VA-/290959472136
I think i saw this guy in an old adapter.
Thank you pwillard.
What you bought was NOT a power supply. It's part of a power supply. A transformer is also NOT a power supply. (Some people who don't know anything about electronics incorrectly call a power supply for a laptop a "transformer".)
I recommend you get a power supply that's safely enclosed unless you are going to mount it inside your own box. It would also be a good idea to get one with the AC power cord pre-attached or one with a standard AC power attachment (like a computer). I don't recommend a "power supply board" or an "open frame power supply" unless you know what you are doing! (You can also build your own power supply from scratch if you know what you are doing, and know how to make it safe.)
For expermintal purposes (or prototyping, breadboarding, etc.) the best solution is a [u]bench supply[/u]. You may not have the budget, or the need for a bench supply, but that's the ideal... They are generally "bullet proof" (you can short them out without damaging them), they are safe, and you can get them with multiple-adjustable voltages, etc.
I built a basic bench supply, but I rarely use it. Most of the time when I'm building a project, I just build the power supply first. (It's getting to the point where it's sometimes cheaper to buy a power supply than build one.)
Wow ..... i wonder if thermal shutdown occured on the lm317 
I want to know what survived lol
Actually, i can get the resistance from nearly all parts. I will try them later if they work 
/nothing/ on that board would have survied 230V house current. If no tracks are blown off the board, something else gave way, not only the cap ... Toss the board and learn about elementary electricity and safety
Sorry to sound like an old fart, but please be safe!
// Per.
Dear Zapro, i have been searching around nearly 1 year to find a course or someone to teach me about the basic electricity but i couldn't 
I can't believe that there isn't enough people to start a course.
Do not ever use a 240vac plug (until you know what you're doing lol)
Stick to low power dc 3 - 12v, you need to buy something called a transformer which steps down, like the lm317 they both step down voltage in completely different ways, any electronic device which plugs into a wall socket, generally square plastic box that converts 240ac down to say 9v it could be anything eg 3v or 24vdc .. direct current vs ac (alternating current)
Then you supply THAT low voltage DC current say 9v to your lm317 then you can convert dc to dc all LOW voltages.
Google anything you don't understand eg "transformer"
I know this rule anymore, i am sitting far away from the plug
Thank you for the info cjdelphi.
