11-04-2014, 08:57 PM
...or you have a cathode to heater or short in that tube.
Try another known good 7X7 tube and see if the hum stays away.
Chuck
Try another known good 7X7 tube and see if the hum stays away.
Chuck
Chuck Schwark,
The Philco Repair Bench
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http://www.philcorepairbench.com