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#1
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buying NOS tube ~ fails tester ~ oh the joy
Just got a 5814 / 12AU7 in and tested it on my tube tester according to
the setup instructions on the tube list that comes with the tester. Sencore Mighty Mite II, TC 114. Of course the tube was sold as NOS, however, an odd thing happened when I tested it. Both sides fail. There are no shorts or leakage and my tester was calibrated, albeit a year ago, and tests all my other tubes, 12AX7, 12AT7, EL34, EL84, 6L6GC fine and has properly indicated new and used tubes as well as shorts. So my questions is this, might the setup data be wrong. All that changes from a 12AX7 is the plate load goes down one click and even testing it as a 12AX7 it only passes minimally. Could there be some reason other than DECEPTION on the part of the seller as to why this tube is failing. HYPE (grandiose marketing) in my book is as good as deception. We're talking this tube has seen at least 1,000 hours to not be in the green on my tester. That far exceeds using a tube briefly not liking it and still claiming it's NOS. ------------------------------------------------------------ Here is what I wrote the seller: Got the tube today. It was boxed very nicely and shipped promptly. The 5814 doesn't pass as per the photos of it being tested. There is no leakage and there are no shorts so somehow this tube is testing as well used as opposed to New Old Stock. Any enlightenment or commentary would be appreciated. I am not the end all know all regarding tubes and any information you can provide regarding how you acquired it, stored it etc. might lend an explanation to why the tube fails. ------------------------------------------------------------ Do I return it or do testers sometimes not tell the whole story and this tube may very well be NOS - the getter flashing is 110% intact and thick. |
#2
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you see, this is why I advised you to get a REAL tube tester, rather than
that little toy tester you are using. if the tube is boxed, and the flashing is 100%, seller reputable, then it is likely the tester that is your problem about 99% likely 99% of NOS tubes I buy on ebay are truly NOS! get a real tube tester, and get it calibrated \ cheers! cowboy "Ozzy 2005" wrote in message ... Just got a 5814 / 12AU7 in and tested it on my tube tester according to the setup instructions on the tube list that comes with the tester. Sencore Mighty Mite II, TC 114. Of course the tube was sold as NOS, however, an odd thing happened when I tested it. Both sides fail. There are no shorts or leakage and my tester was calibrated, albeit a year ago, and tests all my other tubes, 12AX7, 12AT7, EL34, EL84, 6L6GC fine and has properly indicated new and used tubes as well as shorts. So my questions is this, might the setup data be wrong. All that changes from a 12AX7 is the plate load goes down one click and even testing it as a 12AX7 it only passes minimally. Could there be some reason other than DECEPTION on the part of the seller as to why this tube is failing. HYPE (grandiose marketing) in my book is as good as deception. We're talking this tube has seen at least 1,000 hours to not be in the green on my tester. That far exceeds using a tube briefly not liking it and still claiming it's NOS. ------------------------------------------------------------ Here is what I wrote the seller: Got the tube today. It was boxed very nicely and shipped promptly. The 5814 doesn't pass as per the photos of it being tested. There is no leakage and there are no shorts so somehow this tube is testing as well used as opposed to New Old Stock. Any enlightenment or commentary would be appreciated. I am not the end all know all regarding tubes and any information you can provide regarding how you acquired it, stored it etc. might lend an explanation to why the tube fails. ------------------------------------------------------------ Do I return it or do testers sometimes not tell the whole story and this tube may very well be NOS - the getter flashing is 110% intact and thick. |
#3
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cowboy wrote:
you see, this is why I advised you to get a REAL tube tester, rather than that little toy tester you are using. if the tube is boxed, and the flashing is 100%, seller reputable, then it is likely the tester that is your problem about 99% likely 99% of NOS tubes I buy on ebay are truly NOS! get a real tube tester, and get it calibrated \ cheers! cowboy This toy cost $120 from a reputable seller from rat BUT please continue i.e. real tube testers and calibrated got a link? |
#4
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#5
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This toy cost $120 from a reputable seller from rat BUT please continue i.e. real tube testers and calibrated got a link? Since all of the major Hickok calibrators are no longer calibrating, for one reason or another, I would go for a TV-7D/U or B/U off ebay, and make sure to have calibrated by Dan Nelson it will be substantially more than $120 by the time you are done, but what is a tester that was $3800 in 1963 worth in today dollars? $25,000 ? spend $700-$1000 and have confidence in your results! cheers! cowboy |
#6
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SNIP
it will be substantially more than $120 by the time you are done, but what is a tester that was $3800 in 1963 worth in today dollars? $25,000 ? SNIP $23,818.30 http://data.bls.gov/cgi-bin/cpicalc.pl CPI Inflation Calculator Thanks will check them out. Dan Nelson. |
#7
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Ozzy 2005 wrote in news:sJ_0e.2010$T_6.286
@fe12.lga: Just got a 5814 / 12AU7 in and tested it on my tube tester according to the setup instructions on the tube list that comes with the tester. Sencore Mighty Mite II, TC 114. Of course the tube was sold as NOS, however, an odd thing happened when I tested it. Both sides fail. There are no shorts or leakage and my tester was calibrated, albeit a year ago, and tests all my other tubes, 12AX7, 12AT7, EL34, EL84, 6L6GC fine and has properly indicated new and used tubes as well as shorts. So my questions is this, might the setup data be wrong. All that changes from a 12AX7 is the plate load goes down one click and even testing it as a 12AX7 it only passes minimally. Could there be some reason other than DECEPTION on the part of the seller as to why this tube is failing. HYPE (grandiose marketing) in my book is as good as deception. We're talking this tube has seen at least 1,000 hours to not be in the green on my tester. That far exceeds using a tube briefly not liking it and still claiming it's NOS. While the Sencore is not the best in the world it is OK. I have tested many tubes and never have I seen a case where a tube was good when it measured bad on that tester. I have seen the converse no matter what tester I used. Try bumping up the heater voltage by one click and see if it makes a difference. If it doesn't, then I would say you have a bad one. I have seen brand new tubes be bad. I don't know why some tubes fail at normal heater voltages but pass when slightly higher than normal. Some call that a bad tube I suppose. If you are wondering if the tester is correct, the only reliable way to tell is to test another 12ax7. Anything else is quessing. You should check for socket corrosion and loose pins. r |
#8
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SNIP
seen brand new tubes be bad. I don't know why some tubes fail at normal heater voltages but pass when slightly higher than normal. Some call that a bad tube I suppose. SNIP Checked all that and other tubes are OK so this one has to be bad it appears BUT qualify what you mean by I suppose. If a tube tests below minimum doesn't that mean it won't perform to specification and that using it won't give good results which aren't going to last long anyway as the tube burns to completely kaput. |
#9
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"Ozzy 2005" wrote in message
... SNIP seen brand new tubes be bad. I don't know why some tubes fail at normal heater voltages but pass when slightly higher than normal. Some call that a bad tube I suppose. SNIP Checked all that and other tubes are OK so this one has to be bad it appears BUT qualify what you mean by I suppose. If a tube tests below minimum doesn't that mean it won't perform to specification and that using it won't give good results which aren't going to last long anyway as the tube burns to completely kaput. Nobody has mentioned that a 5814 isn't exactly a 12au7. It is close to a 12au7 but has LOWER transconductance. Kinda like a 5751 is close but not quite a 12ax7. You say it has no shorts... I would call it safe to try in your application and see if it functions properly, do some distortion testing, etcetera and so forth... One of Alan Douglas's books explains why using a tube tester as a gauge of NOS will not work. Tube testers are not capable of doing anything more than providing a rough gauge of tube health, NOT how NOS it may be! -- Alan Gallacher Born to Tinker! |
#10
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If you are going to spend that much, add a couple more bucks and get the
Hagerman VacuTrace. Then you will know exactly what your tube is doing at any operational point. Run curves if you want. Keep the cheap tester for all the non-audio tubes. "cowboy" cacheoverflow@yahooDOTcom wrote in message ... This toy cost $120 from a reputable seller from rat BUT please continue i.e. real tube testers and calibrated got a link? Since all of the major Hickok calibrators are no longer calibrating, for one reason or another, I would go for a TV-7D/U or B/U off ebay, and make sure to have calibrated by Dan Nelson it will be substantially more than $120 by the time you are done, but what is a tester that was $3800 in 1963 worth in today dollars? $25,000 ? spend $700-$1000 and have confidence in your results! cheers! cowboy |
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