©2011 Bob Putnak. I am frequently asked how to test voltage regulator (VR) tubes, which are sometimes called “glow regulator” or “glow discharge” tubes. Few tube testers test VR tubes, and most models that claim to test VR tubes do a worthless job at this task. They use AC voltages instead of DC the AC […]
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Here are a few Q&A’s about a Fisher 500-B receiver: 1) Q: “How do I connect speakers to my Fisher 500-B”? A: This is confusing if you are not familiar with Fisher equipment. The photo below shows correct speaker connections to the 500-B. I have seen other 500-B models with a slightly different layout, but
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Copyrighted by Bob Putnak, all rights reserved. “Sometimes output tubes must be selected which will provide a satisfactory balance adjustment. A tube tester usually will indicate whether a pair of tubes have reasonably similar characteristics.” – Robert Middleton, 101 Ways to Use Your Audio Test Equipment, Howard Sams Inc.[1] “Tube matching” is a controversial and
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Most tube testers were not designed to evaluate balanced plate sections when testing a filament-type rectifier tube. ©2010, Bob Putnak, TubeSound. When testing rectifiers such as 5U4, 5Y3, 5Z3 …have you ever wondered why one plate section tests stronger on your tube tester? Are all of your rectifier tubes really unbalanced? I was recently sent
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This article explains stepper repair of a 1950’s Seeburg jukebox. High voltages are present. Repairs should only be attempted by a qualified technician. ©2010, Bob Putnak. This article uses a stepper from a Seeburg C as the repair example, but the 160/200 play steppers found in late 50s and 60s Seeburgs are fundamentally the same
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