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question about heater supply center tap

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  • question about heater supply center tap

    I'm starting to build a small tube amp from the schem. below. As you can see the heater supply has an artificial center tap that connects to the power tube's cathode. the other end is connected to the heater supply at the rectifier. Does it need to be connected there, or can it connect anywhere along the heater supply? For example, at the power or preamp tube, which would be somewhat more convenient on this point to point project. My gut tells me it's the same either way, but sometimes my gut is an idiot.
    Micro-Champ-R2B.pdf

    Oops! I just realized that schem doesn't have a tube rectifier. So it can connect at the power tube.
    Is there no way for me to delete this post?
    Last edited by dmartn149; 10-22-2015, 11:18 PM.
    Vote like your future depends on it.

  • #2
    Originally posted by dmartn149 View Post
    ...Is there no way for me to delete this post?
    Delete is down in the "Edit Post" path.
    1) Click edit post
    2) Choose Delete on the next screen.
    3) Check the "Delete this post in the following manner" box
    4) Click the "Delete" button (lower right of the screen)

    You have about 24 hours after posting to edit/delete.
    Last edited by Tom Phillips; 10-23-2015, 12:07 AM.

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    • #3
      I think you are a little confused. There is no rectifier in the tube heater supply. The artificial center tap rsistors simply tie to the heater supply at the transformer. The B+ supply may have a tube rectifier or silicon diodes like your schematic. Neither of those affects how the heaters are wired.

      The power tube cathode is just a handy place to "steal" a positive voltage to offset the heaters. The faux center tap is drawn at the transformer, but that is a schematic, not a layout, so electrically you can wire the resistors to any point along the 6v wiring. Fender used to do it at the pilot lamp socket,, but they could be wired to the power tube socket or the preamp socket if you preferred. The type of rectifier the amp uses is irrelevant to this.

      And if you are not aware of it, amps that do have a tube rectifier have a special separate 5v heater winding for the rectifier tube only.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        Thanks guys. I still can't find a delete option on the edit page. That's okay.
        Enzo, yes I realize most rectifier tubes have their own 5v heater supply. Mine is a 6x4, so I was getting the schematic confused with the layout that I have in my head. Where the schem has the heater supply going to the other tubes, my mental note has it going to the rectifier heater first, so I was initially thinking I would attach the ct at the rectifier, but then I realized that it would be more convenient to keep the whole ct arrangement at the power tube socket.
        Last edited by dmartn149; 10-24-2015, 01:02 AM.
        Vote like your future depends on it.

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        • #5
          Originally posted by dmartn149 View Post
          Thanks guys. I still can't find a delete option on the edit page...
          The following post from another thread seems to be the explanation.
          Originally posted by g1
          It is my understanding that you can not delete the original post of a thread with the current forum settings.
          There is supposed to be a forum setting "Can delete own threads" which I believe is turned off.
          I suspect the reason is that it would also erase all responses within the thread (the entire thread would disappear).
          Too much potential for lost posts/abuse.

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          • #6
            Look at it like you were sitting in a tavern. As much as you might like to, once you ask a stupid question, you can't un-ask it.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              Originally posted by Enzo View Post
              Look at it like you were sitting in a tavern. As much as you might like to, once you ask a stupid question, you can't un-ask it.
              Yeah, that's okay. Keeps it real
              Vote like your future depends on it.

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