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"Matched" 3-500Z Tubes

Discussion in 'Amateur Radio Amplifiers' started by VE3XK, Oct 28, 2011.

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  1. VE3XK

    VE3XK Ham Member QRZ Page

    Is a matched pair of 3-500Z required in a Kenwood TL-922 or 922A?

    If so, is there a way of easily testing any pair of 3-500Z for match, or most one buy them "matched" from the tube manufacturer or distributor?
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I don't think the original equipment manufacturers made any attempt to match the tubes; the tubes always came from the same manufacturer and a consistent manufacturing lot (made around the same time period, preferably very close to the same time). Never saw what Kenwood did, but I hung around Henry a lot when they were building dual 3-500Z amps and they just took tubes from the shelf, plugged them in, and used them.:eek:

    RF Parts says they can "match" tubes; seems to me what they do is apply some operating bias and pick out pairs that draw about the same idling current at the same bias level. That may be "matching," but I don't know if that's really effective or not, since when they're idling they're not really doing anything useful.;)
  3. VE3XK

    VE3XK Ham Member QRZ Page

    Thanks for the quick reply. Since there is nothing in the TL-922 Service Manual about matched tubes, it is probably not required. The method you mention is probably not relevant to their actual operation in an amplifier.
  4. KM3F

    KM3F Ham Member QRZ Page

    It would be nice if it were to be done but not in this day and age.
    Matching would be for DC parameters as well as RF output ,but no one is about to do it to that extent.
    Besides unless the tubes are greatly different , you might not recognize the missmatch, then you would still not know which one it is without your own testing in the amplifier.
    Good luck.
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