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Can you test tubes with an ohmmeter for more than shorts?

Discussion in 'Amplifiers' started by Tweetybird, Aug 24, 2019.

  1. Tweetybird

    Tweetybird Well-Known Member

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    The plates in tube?


     

  2. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    You should be able to check the heater filament.
     
    Captain Kilowatt likes this.
  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    That all you can do with an ohmmeter. Check for shorts and see if the filament is intact.
     
  4. Tweetybird

    Tweetybird Well-Known Member

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    I thought there might have been a specific ohm range between pins.sensors I test at work have them I have to call manufacture for specifics. Like an igniter for heater 50 to 75 ohm is good range,will work above 75 ohm but ready to pop.
     
  5. Tweetybird

    Tweetybird Well-Known Member

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    I thought tats what a tube tester checked along with shorts and voltage %
     
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Tubes should show either a complete open circuit or a dead short depending what elements are being checked. Filaments should show a nearly dead short while plate to grid should be infinity. Some tubes may have a grid connected to the cathode and will show a short. You need to know the pinouts of the tube to be sure.
     
    Shadetree Mechanic likes this.
  7. Tweetybird

    Tweetybird Well-Known Member

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    So to properly test a tube requires a tube tester ,not a multimeter
     
  8. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    There are none to call!...
    Those tubes in those amps have not been manufactured since the late '70s early 80's at latest.:mad:
     
    Captain Kilowatt likes this.
  9. Road Squawker

    Road Squawker Sr. Member

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    Sure a lot of trollin goin on
     
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  10. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Other than for shorts....YES.
     
  11. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I'm just waiting to set the hook. :ROFLMAO:
     
  12. mechanic

    mechanic Well-Known Member

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    I bought an Eico 350 tube tester about 15 years ago.... The only good way to check vacuum tubes or also known as valves. The tester will load the tube properly with correct voltages and measure resistances and drops. The only good way to check a tube!
    If a tube has a dull white spot or spots then it has become gaseous, the getter has been oxidized. This is a visual check!
    Vacuum tubes are consumables so they need to be replaced every so often and not many are made nowadays. Thankfully Guitar amps are still being made!
    And I do remember Radio Shack had tube checkers in the store and some drug stores! Where did all this machinery go?

    73 mechanic
     
    Shadetree Mechanic likes this.
  13. nomadradio

    nomadradio Analog Retentive

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    Attics, basements, garages, storage warehouses, the landfill and the occasional antique dealer.

    Sold all of them we had years ago. Some on fleaBay and on Craigslist.

    73
     
    Crusher likes this.
  14. 543_Dallas

    543_Dallas Sr. Member

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    The best way to test a sweep tube is to drop it on the concrete to make sure it's bad.
     
  15. oldtymer

    oldtymer Well-Known Member

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    Sometimes they test good in the tester as there is not a big load on them but will not
    function when placed in the unit and fully driven.
     
    sunbulls likes this.

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