I have a Standel Model 70 on my bench. Missing rectifier tube. Owner says it had a 5U4 but chassis is marked for 5R4. What rectifier(s) can be safely subbed? I have on hand 5Y3, 5V4, 5U4.
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The 5u4 is probably closest in performance, and is piout compatible, but requires about one more amp of 5V wind current. The wind on the existing PT may be overbuilt by enough to handle it though. Plug in the 5U4 and if the 5V reads below spec or the PT gets very hot you'll want to either find a 5R4 for the amp or install an extra 5V transformer for the rectifier filament."Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
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