Tube testers

Discussion in '"Boat Anchor" & Classic Equipment' started by N4KDF, May 25, 2021.

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  1. KN4SMF

    KN4SMF Ham Member QRZ Page

    Well put it this way. If a tube works, I save my spare as long as possible. A weak tube in an AA5 radio for instance that otherwise plays fine, can do no harm.
     
    W7FAN likes this.
  2. WA2CWA

    WA2CWA Ham Member QRZ Page

    In one of my active Heathkit SB-200's, I have two original 572B's which still perform quite well. One of the tubes has a date code of 1966. Out in the real world, there are probably hundreds of thousands of tubes stashed away by probably thousands of people.

    Several years ago, a local radio/TV service shop was shutting down (owner retiring). I wanted to buy all his new sweep tubes but in order to get them, I had to buy all his tubes. I brought them home in two large TV cartons that held 27 inch wood console floor standing TV's. One of these days I probably should go through those boxes to really see what "treasures" I have. At least all the sweep tubes were put into a separate box. :)
     
  3. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    Sometimes a tube tester will tell you something that isn't obvious with in-circuit performance. I recently refurbished the PTO in one of my 75A-4s. I fired it up for a bench test, checking the output with a frequency counter. It seemed stable with little warm-up drift, but the frequency would shift noticeably, several hundred Hz, with even a slight change in nominal 117 v.a.c. line voltage, like only a volt or two. I checked the tubes, and one tested marginal in the TV-7 tube tester. After I replaced the marginal tube with a good one with plenty of reserve, there was was much less drift. I tried putting the bench supply on a variac to see what would happen, and varying the input voltage from around 90 all way up to 130 volts produced only a few Hz drift.
     

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