Still searching for this ground hum issue on a diy build. secondary has no center tap for the 6.3v heater filaments so I put an artificial CT on V1 and not on the pilot light. there are insulators between the wings and the base on the pilot light so the bulb base never touches the bracket holding it and never touches the chassis to ground. I scavenged the pilot light and can not remember what it came from. I can attach a clip to the lower wing that makes contact with the bulb base and the chassis as shown below, and the hum goes away. Can some one take a look at theirs and help me figure out what's going on here?