restoring a Sylvania 620 Tube Tester
I recently restored a Sylvania model 620 tube tester. The manual was dated 1955, so that is the approx vintage. Sylvania describes the test method as “Sylvania Composite Transconductance and Emission.” (Source: Sylvania 620 service manual, page 5). This method is not the same as Hickok’s Mutual Conductance. This is an extremely well-built tester. Construction […]
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