Hello, I am new to the forum. I have three 50w Chinese lasers. Right now they are all down. I have only had one working for the last month and it went down yesterday and I have 25 orders to fill and I am in panic mode. My power supply went out, So I put in a different one in. Now nothing. The used power supply worked when I took it out of an old machine. Fan runs, lights up. Test button does not fire tube, but I put my test meter on the led going to the tube and it is hot. I bought a new tube and put it in and it does not work. Now I don't know is my power supply bad? Is the new tube not good? Don't know which direction to go from here. What is funny is that on all three machines I have the same problem, they run, I get power out of the power supply and nothing out of the tubes. Any ideas. I covered the basics, water flow, ect.