Attachment 266404 Hello, excellent info here. I included schematic of my power supply.... Letters not the same as what you are talking about. I'm having same problem, everything works but no power to tube. Bypassesd flow switch, no other "off" switches on machine (50 watt Chinese)... Test button does nothing, fuse OK in power supply. Tube looks fine, did styrofoam test, nothing happens on red or return wires. So you talk about the K+ lead, I have nothing labeled as such. On mine I tested L and had 4.96 volts, hit test, drops near 0... Then went to IN, which I thought must be the same as K because all the rest are going to ground. Tested that showed 3.56 volts and when I hit test, it actually went up to almost 4. I'm a poor artist and can't afford to buy parts I might not need.... (can't afford one's I do for that matter)...but need the machine working. So it looks like I have at least some power going in. Green light stays on, fan works.... But it does not look like anything is going out... Would this narrow it down to the power supply?