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    Tube Tester

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    bluemeanies

    Posts : 200
    Join date : 2015-02-09
    Age : 67
    Location : Folsom Pa.

    Tube Tester

    Post by bluemeanies on Mon Jan 02, 2017 11:43 am

    Just wondering because of all the talk of tubes on the forum how many people have or are considering to purchase a TUBE TESTER.
    Nothing high end but one that is fairly reliable and moderately priced.
    I have seen a lot of them on E-Bay but i am not familiar with brands and quality.
    I would be interested if Bob jumps in here and or audiobill.


    Thanks

    GP49

    Posts : 782
    Join date : 2009-04-30
    Location : East of the sun and west of the moon

    Re: Tube Tester

    Post by GP49 on Mon Jan 02, 2017 1:16 pm

    Time was, you could pick them up for next to nothing, but no more...

    I have two, both Hickoks.  One was offered to me for nothing, years ago.  The other I took from the basement of a house we were cleaning out.   Another member of this board got hundreds of tubes that were there, too (I kept the NOS Mullard GZ34s!), after I used some of the tubes to test the tube tester!

    Typically, because of the many switches and controls in tube testers, they need to be checked out, and the switches and controls cleaned, at least.  Electrolytic capacitors, as always, should be carefully reformed, or replaced.  They're OLD by now.
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    peterh

    Posts : 873
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Tube Tester

    Post by peterh on Mon Jan 02, 2017 1:28 pm

    bluemeanies wrote:Just wondering because of all the talk of tubes on the forum how many people have or are considering to purchase a TUBE TESTER.
    Nothing high end but one that is fairly reliable and moderately priced.
    I have seen a lot of them on E-Bay but i am not familiar with brands and quality.
    I would be interested if Bob jumps in here and or audiobill.


    Thanks

    Forget it.
    Your amp is a much better and more complete tester, not only can proper idle point ( = voltages on the schematic) be measured, also microphonics and noise is tested.

    And for every tube that is suspect - junk it. Tubes are expendables and new ones can be
    bought for a reasonable sum.
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    Peter W.

    Posts : 527
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Tube Tester

    Post by Peter W. on Mon Jan 02, 2017 6:54 pm

    OK, I will go straight at this one:  

    1. Tube testers are useful if:

    a) One handles either a lot of tubes, or  a lot of equipment that depends on tubes.
    b) One understands what they can, and especially what they cannot do.
    c) The tester itself is fully checked out and is operating as it should.

    2. There are two basic classes of tube testers:

    a) A simple emissions-tester. This, in essence, simply tests for conduction from the cathode to the plate.
    b) A GM Tester that also tests the grid, and tests the tube at a fixed bias.

    3. Within each class of tester, there are sub-classes which actually separate 'good' testers from 'not so good' testers:

    a) A simple emissions tester that also tests (properly) for shorts and gas can be very useful. Shorts must be tested with a *HOT* tube, as many types of short do not show up with a cold tube. and with that group, some do not show up until the tube has been heated a while. So, a tester that can also sustain the filament load and plate voltage for more than a few seconds is worthwhile.
    b) A GM tester that does the same is useful. But, one that also will allow measurements of filament current, plate current, and will allow variable bias and/or an external bias source now has the capacity to do matching. Very, very few testers have these specific capacities. Those that do tend to be stupidly expensive.

    4. Why own a tube tester:

    a) A power tube that flashes over, or shorts in use can cause all sorts of spectacular artifacts. Similarly, a rectifier tube. Small signal tubes less so, but still can have unfortunate effects should they short in use. So, if one has a piece of tube-based equipment, AND a tester that does shorts and gas, one has the ability to screen the tubes to some degree before applying power to the device.
    b) If one is into audio at a serious level, it can be quite useful to determine if any tubes, especially power and rectifier tubes, are marginal. And similarly small-signal tubes are doing as they should. This settles many otherwise indeterminate questions - is it the device or the tube(s)?

    5. Observations:

    a) I keep several dozen tube-based radios from 1919 through 1963. I have several thousand tubes stored away. With all that, my simple Simpson emissions-tester is sufficient for 90+ % of what I do with tubes, as it does an excellent job with shorts and gas, and can sit with a 6550 in the socket for as long as an hour and not overheat. What it will NOT tell me is anything other than gross differences in quality between any two tubes.

    http://radiolaguy.com/images/equipment/Simpson_555-p.jpg  

    b) I also keep a Hickok 539B, fully calibrated and obtained legitimately from GE Re-Entry Systems in Philadelphia some years ago. This tester has all those obscure capacities and can match tubes effectively. It can also determine quality differences between tubes effectively enough that a decision to scrap or continue-in-service may be made on a sound basis. I use it about 10% of the time I am screening tubes.

    http://jimmyauw.com/wp-content/uploads/2010/01/hickok-539b.jpg  

    I deal in more than a few radios that use both rare and exotic tubes such that junking a tube merely because it is suspect is not an option. Eye tubes, and some power output tubes fall into that class, as well as some of the pre-octal tubes that were never made in vast quantities. Check out a 6T5 some day if you want a perfect example. So, to that end, a tube tester is a useful tool, mine have paid for themselves many times over. And, the first blown output or power transformer from a slagged tube (heat-related short) handles any other doubts one might have.

    Conclusions:

    a) Any tester contemplated *MUST* test effectively for shorts and gas. Otherwise, it is pretty useless for reliable screening other than go/no-go - and most of the time that can be done with a VOM.
    b) Unless one is heavily into tubes and understands the multiplicity of types and applications, an expensive GM-type tester is probably not a good investment.
    c) Military testers (The Hickok-pattern TV7 being a prized example) were designed for a very specific purpose under very specific conditions and generally not much more useful than an emissions tester in the world we inhabit. Yes, they will differentiate to a much finer degree tube *quality* (term-of-art meaning how close to new-spec. any given tube might be, not how well it is made). But it is not useful for matching purposes and cannot be made to be so. So, unless one is committed to a lab-grade unit, a higher-end emissions-tester (REPEAT: SHORTS AND GAS) will be sufficient.
    d) Unless one purchases a 'new' computerized tester (and, yes, those are still being made with quite a few options), the typical tester one sees on eBay is starting at 50 years old, and counting. Well made testers, like well made anything elses, will stand the test of time and are readily maintainable. But, unless one gets a tester from a reliable source and/or REALLY understands complex troubleshooting,

    http://i.imgur.com/XWylh.jpg?1  

    this is not an exercise for the faint-hearted.

    I paid $15 + about 4 hours for my Simpson.
    I paid $100 + about 8 hours for my Hickok.

    Purchase ONLY from reliable instrument makers. And there is a truism amongst tester users:

    Accurate/Supreme/ HiTech et.al. aren't.

    Reliable brands (most of the time) are: Hickok, Simpson, Heath, Eico, Jackson and a few others are good points of departure.

    e) Equally as important as any given tube tester is the paper that comes with it. Which must have, but not be limited to: A complete owner/shop manual. Obsolete tube data. Updates at least into the 1980s, if not beyond. Data sheets for WE (Western-Electric) pattern tubes. Sockets or adapters for 4-pin through Nuvistor tubes. And Euro-pattern tubes if one is into that as well.

    Of the brands named above, all of this is available for all of them in the after-market.

    Enjoy!


    Last edited by Peter W. on Wed Jan 04, 2017 2:31 pm; edited 2 times in total

    setu

    Posts : 5
    Join date : 2013-03-11
    Location : California

    Re: Tube Tester

    Post by setu on Mon Jan 02, 2017 7:00 pm

    I use B&K 747B (1976 model?) to match PAS3X,ST70,FM3 etc tubes by transconductance.
    Admittedly during testing the plate voltage is not high (as in actual operation) but it enables me
    to choose/evaluate/match tubes....
    Some Dynaco specs are 5% tolerance-----so I try to match there at <1%.
    Same strategy for tube-matching.  

    My solid-state 747B calibrated VERY easily in 2011 so it does not yet need repair.

    Warning: it is worthless without a manual
    It will test Russian 6P3SE-EV/EL34 etc but not 300B
    Since some very-old/new tubes wont be in a 1976 tube manual/settings chart you might not be able
    to test those without knowing equivalence.

    I had a bad Sencor once that mistakenly sent some good Telefunken 12AX7 to trashcan--ouch!
    There are lots of old switches,contacts etc that probably need contact-cleaner/maintenance etc.
    I use CRC non-residual spray although some like Caig.

    Yes, our ears are the real tester.
    Strangely I have had tubes testing in the red/reject zone of meter that still sound good...

    You can avoid buying costly tube-tester if you buy tubes from trusted vendors(Kevin Deal,McShane etc) who match
    and use more sophisticated tube-testers.  I needed a tester because I get used tubes from Russia,
    auctions, flea-markets....  I buy them based on price,brand,mood,superstition....  
    Also musicians will appreciate you when you can test their EL84,EL34 etc for them.


    Last edited by setu on Mon Jan 02, 2017 10:38 pm; edited 1 time in total (Reason for editing : omission)

    Jim McShane

    Posts : 191
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Tube Tester

    Post by Jim McShane on Mon Jan 02, 2017 7:51 pm

    This is a VERY complex topic!

    I agree that for most people a decent emissions tester with good shorts/gas (grid current) test capabilities is all that is needed. You can do some "tube testing" in your amp but it is risky! A shorted or gassy tube can do a lot of damage in a hurry! Checking with your amp becomes a pricey and unpleasant experience if that occurs. Oh - and RARELY do different tube testers give the same readings!

    You CANNOT effectively match tubes for use in a power amp output section with but a handful of tube testers. MATCHING FOR TRANSCONDUCTANCE OR EMISSION ONLY IS RISKY!! Unless the power tubes can be checked/biased individually it is easy to have one tube just loafing and one become a current hog. The result of that is the "hog" has a short and unhappy life in many cases.

    Two last thoughts for now - first, VERY few tube testers exist that don't have a learning curve. Just setting up the switches and reading the meters will not give you enough info to make asn intelligent decision in many cases regarding a tube's performance, There is a lot of interpretation of data that is needed to do a top shelf job. I've got close to 40 years of tube testing experience and I STILL learn something new all the time! Second, you may find you need multiple testers to cover all the different tubes you may want to test. I know of NO tester that can test all the tubes out there.

    By the time you add up the costs of purchasing and owning a tube tester you might find it's much costlier than simply getting well matched tubes from a good, solid, reliable source.
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    Kentley

    Posts : 436
    Join date : 2015-03-06
    Age : 65
    Location : Worcester, MA

    Re: Tube Tester

    Post by Kentley on Mon Jan 02, 2017 8:14 pm

    "By the time you add up the costs of purchasing and owning a tube tester you might find it's much costlier than simply getting well matched tubes from a good, solid, reliable source." - {Jim McShane}

    And there is no gooder, solider, reliabler source that Mr. McShane hisself, IMHO.

    Jim McShane

    Posts : 191
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Tube Tester

    Post by Jim McShane on Wed Jan 04, 2017 12:15 pm

    Thank you so much - that is so kind of you Kentley! I do my best, that I can promise you!

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