Dumb question - sorry

Discussion in 'Tube Audio' started by samwise801, May 17, 2018.

  1. samwise801

    samwise801 AK Subscriber Subscriber

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    But can I swap tubes in and out of, say, a pre-amplifier (in my case, a Conrad Johnson PV-12) while the unit is powered off, but still plugged in, without issue? Or is it recommended to unplug the sucker first?
     

     

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  2. primosounds

    primosounds SE KT120 w/ 6J5G drivers. LCLC ps + 2 x 5ar4 Subscriber

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    Sure there is no issues that i am aware of doing that.
     
  3. UncleBingo

    UncleBingo AK Subscriber Subscriber

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    I would turn the power amp off, too. You don't want a big transient or full blast noise bomb hitting your speakers.
     
  4. samwise801

    samwise801 AK Subscriber Subscriber

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    Fair enough. But so long as everything is powered off, I'm okay "tube rolling?" I shouldn't need to unplug everything too, or otherwise take any add'l steps?
     
  5. primosounds

    primosounds SE KT120 w/ 6J5G drivers. LCLC ps + 2 x 5ar4 Subscriber

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    You mean while all your other equipment is powered on? Yes, if you want to switch out tubes in the preamp, turn it off and switch the tubes after about a minute, careful they may be hot, and then you can turn it on. Should be no problem doing that.
     
  6. maxhifi

    maxhifi AK Subscriber Subscriber

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    If you have to remove a cover to access the tubes, and there's any chance to touch any of the internal wiring, I would strongly suggest to unplug the preamplifier from the wall outlet.. Don't forget that tubes operate at voltages which can be lethal to humans, so unless you're an experienced tech, I would never suggest changing tubes in a unit which is plugged in. Also, you shouldn't operate the preamplifier without covers installed, for similar safety related reasons, not to mention shielding.

    No need to disconnect patch cords or any other non power wiring. If the tubes are accessible without removing any covers, just shutting off the power is sufficient. Be careful to let the tubes cool down before you pull them out, it isn't good to handle hot tubes too much. (they can be damaged, and so can your hands!)

    Also, before you get too obsessive over tube rolling, be aware that tube sockets can get worn out from this practice - it's better to remove and install tubes as seldom as possible to keep the sockets in top shape.
     
    Last edited: May 17, 2018

     

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  7. AdamAnt316

    AdamAnt316 Collector of heavy things Subscriber

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    As long as you keep your fingers away from the power cord wires (and the power switch), it's OK to replace tubes in a preamp which is turned off but still plugged in. Might not be a bad idea to drain the filter caps, if you can access them.
    -Adam
     
  8. samwise801

    samwise801 AK Subscriber Subscriber

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    Awesome. Thanks everyone for the help!

    Yes, I do have to remove the cover to access the tubes, but the inside is pretty sparse and the tubes aren't hard to grip firmly w/o even getting close to other components.

    And thank you for the tip on not removing / installing tubes too often. I'm sure plenty of folks out there have equipment that's otherwise in great shape, but with worn / loose tube sockets. Sounds like a bummer!
     
  9. maxhifi

    maxhifi AK Subscriber Subscriber

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    Yep, I serviced some VTL amps where if you turned it upside down, the tubes would literally fall out! I managed to tighten the sockets, but that's a temporary fix, they will never be as good as before.
     

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