Tell me about my new Tube Tester (AVO Mark IV)

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ajbergren, Jan 10, 2008.


  1. ajbergren

    ajbergren Member

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    Today I scored some more NOS tubes, and a tester to boot! All of this was free of charge (I insisted on paying, but they would not accept)!
    :dude

    Anyhow, this tester should be useful for testing all the NOS tubes I obtained in the last week. These include 3 new Mullard 12AX7s (10M series), 2 GE 12AY7s, some Marconi 12AX7s, a pair of Sylvania 6L6GCs, German Siemens 12AT7s, and many others! I will probably start another thread on this since some of the labeling is confusing. For example, the Mullards came in Siemens or Sylvania labeled boxes, with B & L labels, and I can't find any info about these. Also, just for my own curiosity, I would like to ID years of production, etc. (I am a very curious person!)!:crazy

    The biggest issue for now is learning how to use the tester. I have all the manuals, and a whole bunch of other reference data (this gentleman gave me a GE tube manual, and several others including a tube cross-referencing guide and several AVO books).

    As far as I know, the tester is in fine working order (even has a 3-prong plug). However, before I plug it in, I am wondering what I look for. Then, how do I go about using it? Do I just plug in a tube and "hit go?":eek:

    I am nearly new to the NOS tube thing, and completely new to tube testers, so any help would be appreciated.

    Thanks!!!
     
  2. V846

    V846 Member

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    I'm jealous !!AVO are considered to be one of the best by some though I'm not familiar with the different models.Read the manual before testing tubes :nono if you set the thing up wrong such as the heaters you could ruin the tubes or fry something in the tester.

    db
     
  3. SatelliteAmps

    SatelliteAmps Member

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    Read the manual. There should be some basics about operating the tester itself. Usually with tube testers, you plug the unit in, then turn it on. If it is valve based, you wait while it warms up. Some models have to be zeroed, to make sure you get an accurate reading. Then, you look up the tube info you want, and set all the dials, levers, and/or switches to the correct settings. Then you test the tube. In testing a 12AX7 for instance, there are usually a number of tests that have to be preformed (how exactly depends on the individual tube tester). This should all be explained in the manual.

    If a tube is dead, throw it away or mark it so you will know it is a dead tube.
     
  4. teleman1

    teleman1 Member

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    Tubes need to be disposed of properly. Mercury and other stuff may be in them.
     
  5. SatelliteAmps

    SatelliteAmps Member

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    True. My point was not to keep dead tubes as some people will even after testing them. Usually because they are "vintage" or a certain brand.
     
  6. GearHeadFred

    GearHeadFred Member

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    My advise is to practice on some recent production Chinese tubes! Don't put the NOS Mullards under test until you have it down!
     
  7. HCStraub

    HCStraub Member

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    I used to repair testers(mostly Hickok) and collected a lot of them. I have had several AVO's, but got rid of them years ago. They are THE best tester testing tubes under real world conditions and matching power tubes. That being said, they are also one of the SLOWEST testers for testing tubes. Get the manual and read it. These are VERY complex testers and not 'plug n play'.Take your time, make sure you set them up correctly and doing it IN THE RIGHT ORDER. IF you make a mistake it is very easy to blow the meters on those.....replacement meters are impossible to source so be careful. Follow the steps and take your time.
    That is an expensive and complex tester for someone starting out, you really jumped in the deep end.
     
  8. HCStraub

    HCStraub Member

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  9. ajbergren

    ajbergren Member

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    Thanks to all!!

    I now realize that this is an expensive and complex tester, but it came to me free (it was going to be trashed). This was the only one

    I fired up the AVO, and followed the instructions, step by step. I used a sovtek 12AX7 tube, just in case something went wrong (not sure when I'll feel comfortable testing the Mullard 12AX7s or Sylvania 6L6s).

    I got through the initial stages just fine, but have just a couple of questions:

    Step 6: set the A1A2 normal/unlimited switch to the appropriate position for the value under test.:confused:

    What does this mean?

    I quite at this point, and this is just before testing of the mutual characteristics comes. I read through that part, and it looks pretty simple, but I wanted to be sure and have the A1A2 switch set correctly. I will continue to look through the manuals, but any quick tips would be great!!

    Thanks again!!
     
  10. ajbergren

    ajbergren Member

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    Okay, here is what the manual says:

    When testing valves having dissimilar double electrode assemblies it is necessary to limit the anode voltage on the selection not under test. The A1A2 normal position on this control in conjunction with the electrode selector switch, provides the facility for inserting a suitable limiting resistor in the appropriate anode circuit. Thus when testing double valves (triode hexodes, triode pentodes, etc.) this control is switched to the A1A2 normal position. For single and double valvles having identical sections, this control is switched to the Unlimited position. The control is inoperative when testing diodes, rectifiers, etc.

    I interpret this teo mean that it should be in the umlimited position for testing 6L6s, 12AX7s, etc. since these either have only a single element or two identical elements, right?

    Thanks!!
     

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