True! I changed the value of the fixed resistor with a 120 ohm one at the pot with a 4k7 one (since I did not have the exact components) and it worked! Thank you so much!
I took a quick look at the datasheet and the 2N3055 is rated at 15A so that's good.
The max current isn't the only rating to worry about - secondary breakdown is perhaps more likely to happen in high power circuits, so I'd first check the secondary breakdown(aka SOAR) graph.Commercial bench power supplies switch transformer windings to help with efficiency andalso to avoid secondary breakdown becoming an issue (by keeping the max Vce low).There are much better transistors available today than the 2N3055 BTW...
I dont worry about this. The original PSU worked at 22V 4 amps from 36 volts unregulated. I dont plan to draw more than 1.3 A of current.