Tube Tester Question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by K-man, Jun 9, 2006.

  1. K-man

    K-man Member

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    I picked up an old tube tester from a friend of my Dad. Nothing fancy, it's from a company called Accurate Instruments out of NY. It tests for shorts and emissions.

    Anyway, I have no idea how to read the meter. I tested a bunch of tubes that were supposedly NOS or lightly used. The meter has a scale of 0-100 with bad from 0-40, ? from 40-50, and good from 50-100. All the tubes I tested were between 50-70. Shouldn't a NOS test close to 100? Either I'm not reading it right, I got screwed from the dealers I bought the tubes, or the tester needs to be calibrated. Any ideas?​
     
  2. K-man

    K-man Member

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    I read the instructions. They just tell you how to set up the tester to test different types of tubes. Nothing about interpreting the results.
     
  3. clothwiring

    clothwiring Supporting Member

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    I have an old tester, luckily the instuctions are part of the machine (internal scroll wheel - very cool).
     
  4. Matt H

    Matt H Guest

    i find tube testers, especially emissions-only ones, pretty worthless if you want to take some kind of discreet meaning from the results.

    but- if you take a few tubes (say, NOS that sounds great, a questionable tube, and an almost dead tube), you'll get a feel for what the ranges mean in the real world.

    (again, not the emissions testers are really, er, good for much beyond verification of a working tube).

    but still- it's a start.
     
  5. Blue Strat

    Blue Strat Member

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    Emmisions testers aren't known for being particularly useful, except for screening for shorted tubes.

    That said, every tester I've ever used (I've tried many and use 4 different ones in my line of work) has it's quirks. You have to learn the range of readings for a particular tube type. For example, 12AX7s will have a low to high range for new tubes. Test as many new tubes (including modern production tubes so you're absolutely certain that the tubes are new) and keep track of the range of readings you get. Different brands will have different ranges and the ranges will overlap.

    You'll need to test at least 10 12AX7s (or other tube type) of every brand to get a handle on what the acceptable ranges are.
     
  6. K-man

    K-man Member

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    Thanks guys. I'm not planning on going into the tube dealing business, I just thought it would be fun to play around with. Then I got nervous when NOS tubes weren't testing at 100. At least they seemed consistent, testing around 70. I tested some new production tubes and they were in the same range.
     
  7. Blue Strat

    Blue Strat Member

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    There ya go. The numbers have no "absolute" meaning, as in "u factor" or anything like that.

    Enjoy.
     
  8. rockon1

    rockon1 Member

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    I have an Eico 635 tester. Simple emissions tester. Never had a tube test at 100. All my new tubes test around 60 to 70.Most of my old stock test around the same however some test borderline or in the ? range but I doubt they are bad seeing that the highest Ive ever read was 75.When I have a fairly rare GE black plate(or something similarly rare) read in the ? range on a questionable tester I just dont throw it away. Its probably got a lot of life left in it.Wish I had a calibrated ,better tester!
     
  9. minesaguinness

    minesaguinness Member

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    Hello - I'm new here, but been around bit.

    I use an old Naval Pattern Valve tester which is good enough to find out if they're OK or not... works a treat - as a preventative measure (shorts etc), and is good enough to roughly match power valves. The data book with it is extensive and it only takes 5 secs to calibrate and get an idea of good or not.
    I don't know too much about the tester you have bought but I would expect the company to supply instructions on how to adjust FSD for particular valve (sorry tube) types.
    Cheers
    Brian

    [​IMG]
     
  10. samwheat

    samwheat Member

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    You honestly expect an analog instrument to be accurate without recent calibration do you?
     
  11. K-man

    K-man Member

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    I didn't know what to expect, as I'm no expert and had never used one before. How do you calibrate one?
     
  12. samwheat

    samwheat Member

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  13. minesaguinness

    minesaguinness Member

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    Is that one for me?

    My tester is fairly straightforward to calibrate....

    ..... just because kit is old doesn'y mean it can't be calibrated - Avo made some of the best test equipment of their day.

    Cheers
    Brian
     

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