Solving SCR Circuit Problem - EE Student Seeking Help

[tanky322]

I came across a circuit online to vary the 220V input into a welder. This is done to control the amount of current entering the piece being welded, using a foot pedal. The circuit has worked for many people.

I built the circuit, but it doesn't work. R2 blew when I would crank the pot up, and there was no current entering the welder. I don't know if the SCR fired or not, but it wouldn't weld or make a spark what so ever.

My initial thoughts are that the circuit was designed for a particular type of SCR, and mine isn't compatible.

Also, I am an EE student but I am just starting out, I have some circuit theory under my belt, but I am not sure on what to use as a voltage in this circuit, as its all part of the 220V line.

Can anyone help me out?

Sorry for the size of the pictures, but I wanted to keep the detail.

Thank you!

 

[capnahab]

In my lifetime I have worked on all kinds of complicated equipment, including welders and they are the worst because they are a basic power supply.