Crooked Vacuum Tube?

Just wondering if this is an issue or not. It's a 12AX7. I'm going to speak in very technical terms here because I'm a tube guru so let me know if I need to dumb it down.

You know how the pins on the bottom have wires on the inside that go to the bottom plate type deal? That lower plate does not go straight across the tube, it's higher on one side than the other. I only looked at it for a few seconds before packing up to come house/dog sit at my friends so it's not in front of me anymore. It could have been that all of the internals were a little crooked. I even think I remember that the pins that stick out the bottom were longer on one side than the other so if you set the pins on a flat surface the glass looked like it was crooked too but I can't really remember those few seconds very vividly.


  • pitdogg2pitdogg2 Posts: 14,715
    edited October 17
    LOL tube guru.... So let me dumb this down the bottom mica is offset in the tube envelope? The top mica and plates are all off to one side. You do realize these are mostly all hand made correct? As long as the pins make contact correctly in the socket and the tube itself is not microphonic I'd think all is good.

    I've seen more than one tube not sit even on a table because of the way the last piece of glass is melted in place as they seal the vacuum into the tube.
  • mhardy6647mhardy6647 Posts: 23,454
    I wouldn't worry about it as long as the tube works properly -- but if it causes you (the OP) aesthetic outrage, then you might want to replace it. :)

    Even in the days when tubes were mass produced (for better or worse!) and QC was -- perhaps?!? -- more stringent than today... crooked tubes happened sometimes.

    That said, the internal tolerances of vacuum tubes are very critical for them to perform as intended (i.e., meet their electronic performance specs) and, sometimes, even to work at all.

    The RCA receiving tube manuals explain this in a pretty clear and direct way -- although, of course, those manuals are also marketing documents designed to make RCA look really good as makers of tubes! :) RCA Manuals can be downloaded from Pete Millett's outstanding website
    specifically, see


  • mhardy6647mhardy6647 Posts: 23,454
    edited October 17
    Here's a actual, and decidedly vintage, example.
    Not sure how obvious it is from the photo but this Sylvania 5V4 HV full wave high voltage rectifier's guts are decidedly crooked. The guts are tipped 'to the right' relative to the glass envelope as the tube is oriented in the photo.

    The tube works fine but looks a little... umm... handicapped when installed in an amplifier. :| The issue is strictly aesthetic, though.


    On the bright side, I acquired this particular 5V4 for $1 as a used/"plinker" tube at a regional ham radio swapmeet a coupla years back -- it was well worth a dollar as a spare, because it tests, and works, as new. :)
    Post edited by mhardy6647 on
  • NightfallNightfall Posts: 8,505
    I will be your Padawan, teach me guru. ;)
    afterburnt wrote: »
    They didn't speak a word of English, they were from South Carolina.

    Village Idiot of Club Polk
  • michaeljhsda2michaeljhsda2 Posts: 1,932
    Note that the OP's signature is a link to a website.
    SDA SRS 1.2TL's
    SDA 1C's w/Clarity Cap ESA; PA, Mills, RD0194-1's
    SDA 2B TL's w/RD0198-1's
    Yaqin MC-30L integrated tube amp
    Yaqin MS-20L integrated tube amp
  • pitdogg2pitdogg2 Posts: 14,715
    Note that the OP's signature is a link to a website.

    I noticed that hence my LOL
  • mhardy6647mhardy6647 Posts: 23,454
    Note that the OP's signature is a link to a website.

    derp. missed that.
    You mean we've been spammed again?!
    Here I thought it was a legit, albeit wry question.

    Well, still gave me an excuse to post a photo of a crooked rectumfryer rectifier.
    Could be worse, I guess.
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