This video demonstrates the effects of EMI when the tube shield is not grounded. If you have never built a high voltage tube circuit, get an expert to train you. These circuits are easy to build, but the voltages and current are lethal. There are lots of good books out there and SAFETY can NOT be compromised. With this warning made, this is a cool video about EMI (or what happens when your circuit has EMI).
10 май 2012