|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
221.169.100.226
Most ebay seller doesn't state minimum value and Nos value of their tester, so I cann't know the exact condition even we know the test data, may we conclude them by ourselve? May I have min value & Nos value of ecc81, ecc82, ecc83, 6dj8, e88cc, 6L6/KT66, el34/KT77, 6550, KT88, ,5AR4, 5U4, 300B of your tester?
Follow Ups:
Sorry for my poor English, what I means is Min/NOS datas of every tester, like data on my TV7B/U:ECC81: 50 min/ 80 NOS
ECC82: 56 min/ 90 NOS
ECC83: 32 min/ 50 NOS
Ecc88: 62 min/ 100 NOS
E88CC: 50 min/ 80 NOS
6L6: 25 min/ 40 NOS
6CA7: 30 min/ 50 NOS
6550: 44 min/ 68 NOS
5AR4: 40 min/ 60 NOS
5U4: 40 min/ 60 NOS
300B: 58 min/ 90 NOSMin data is what state on book while NOS data come from my experience testing tubes.
May I have min data/NOS data of your tester? like models of Hickok, Eico, Avo, B&K, Heath, Funke, Nueberger.....
Ronaldo
The first tubes you mention which are preamp tubes will not get much data from even the best testers for all paramaters of the tube.
How many times have we put 12ax7s in a tube tester and have them read 25% of new and yet perform perfect in a preamp..By the same token I have seen high testing mullards or RCA 12ax7s only to be microphonic as hell when put in a circuit.
If your buying high priced preamp tubes used,always go to a reputible seller..I get a higher price when I sell my 12ax7 telefunkens becuase my testing not includes emissions and leakage and shorts and mutual conductance,but I also have a signal generator hooked up to both sides of the tube with a set of high impedance headphones and while Im injecting a 5khz signal into the tube for about 40 minutes straight while periodically tapping the tube and listening for microphonics..if I hear any then the tube gets rejected.This is the only way to test real functionality.. I have it set up so I can do this on my heath tt-1 and my sencore mu 140.
I sold a pair of Mullard ECC82 on ebay. These were not like new tubes & usually below spec of what I normally sell. However, they tested close to new gm specs & were not GE late 1960s tubes vplus held up well on the reduced filament 'life' test. The buyer applies their tests via a tube tester and states these are well used tubes. Their tube tester is NOT a good test, just a weak approximation of remaining tube life. To get away from an ebay negative, I had to refund the full amount. I am sure they are enjoying the tubes, however the A$$ was sent to my blocked bidders list.
I know, but at least good testing result "normally" represent good tubes, I buy 200 items last 2 years, when seller say test NOS only 5% disappoint me while 50% tubes fail when ebay seller state "my tester broke" or "I didn't have tester".....
Ofcause, a reputible seller like deserve higher bid, but when we found something too rare or item I look too long, it sometimes deserve some risk.
There's a seller who says, "I usually test tubes from my stash just before I use them, so these aren't tested, but they should be good."
I usually consider 80% per Hickok specs as minimum good. Example: 12AX7A new=1250Gm, 1000Gm=minimum good.
Hickok TV2? May I have the GM value of new tubes I stated before?
Regarding oxide cathode filament tubes only.Ask seller to measure the tube at 5 volts for a 6.3 volt preamp tube. If the reading drops just a few percent or no drop at all from the 6.3 volt measurement, it is a good tube with some reasonable life left. If tube drops to weak, it is on its way out as a bad tube.
Power tubes are more forgiving of this test & 4.2 volts is a better test for a 6.3 volt power tube. Again, a healthy tube should not drop any or very little at the lower voltage.
Every model tester will have a different value for Good/Bad.There is no "standard' and the test numbers are all dependent on what kind of tester was used.
Using a tube tester to gauge "NOS-ness" is folly as transconductance can and will vary widely amongst different brands of the same tube type.
Since tubes do not wear out in a linear fashion a tube that tested on the low side but still good can run many thousands of hours and still test on the low side of good the whole time.
One must remember that most tube testers were designed to weed out defective and worn out tubes on service calls, not gauge "new-ness" for sleazebay sales.
--
Al G
Born to Tinker!
This post is made possible by the generous support of people like you and our sponsors: