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5R4 substitute

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  • 5R4 substitute

    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.

  • #2
    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

    "If you're not interested in opinions and the experience of others, why even start a thread?
    You can't just expect consent." Helmholtz

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    • #3
      Thanks for the info, Chuck.

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      • #4
        You can use the 5V4 with no penalty. It may raise your B+ a little bit. The 5R4 does the same thing as a 5U4 GB but it imposes a much lighter filament current load.

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        • #5
          Thanks, Prairie dawg. I stuck the 5V4 in and heard very loud humming. May be time for a cap job!

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