Tube Short?

Discussion in 'Amateur Radio Amplifiers' started by WQ4G, Nov 10, 2019.

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  1. WQ4G

    WQ4G Ham Member QRZ Page

    Greetings to all:

    Can a 572B (Chinese version by appearance) have an intermittent Grid to Plate short? Or a 'soft' short - one that does not necessarily trip circuit breakers, blow fuses, or melt wires? Can the short be located in the base?

    Also, what makes a tube 'rattle' (my terminology) if there are no apparent loose parts on the inside of the glass envelope? Is there anything in the base that could become loose and make noise when the tube is shaken? Isn't there some kind of compound, in the base, that the tube sits in? Can that become fragmented and rattle? Can that cause a short? Does a rattle render the tube NO GOOD?

    I can see one lead, in all the 572B I have, has an insulation material over it. I see it in a pair of Cetrons I have and I also see it in the Chinese tubes. Except in the Chinese version the piece of material is longer and touches an adjacent lead. Could this cause a partial or intermittent short? The end where it touches adjacent lead appears burnt (darker in color). Is that evidence of a short or is that a result of the heat generated by the tube?


    Dan WQ4G
  2. N8FVJ

    N8FVJ Ham Member QRZ Page

    The tube could have an intermittent short, but would be a grid to filament, not grid to plate at least inside the plate itself. A loose piece of grid wire exposed to the internal magnetic field can move around. A poorly assembled tube could have a short at the base wiring or an insulator breaking down under high voltage. I would toss the tube away.
    K2XT likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    "Tube short?"

    I can always tell if a tube is short by using a ruler to measure its length.:):p
    WQ4G likes this.
  4. K2XT

    K2XT Premium Subscriber QRZ Page

    Steve, Definitely do NOT quit your day job for stand up comedy.
    WQ4G likes this.
  5. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    I don't even think he should do sit-down comedy.
  6. K6CLS

    K6CLS Ham Member QRZ Page

    "They laughed when I sat down to do comedy"
  7. KN1M

    KN1M Ham Member QRZ Page

    As a rule, I rarely use a tape measure.
  8. WA9SVD

    WA9SVD Ham Member QRZ Page

    I think he said a "tube short,o_O" not a "short tube.":D:rolleyes:

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