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Tube experts ---Chime In Do BK testers Lie?

Recently I ordered 50 Sovtek 6550 tubes from a seller on ebay. I later found out the seller was a former employee of Audio Research who bought their stock of 6550s which were overstock from the 90s and never used.

I received the first box of 25 tubes and using my tube tester, a BK DynaJet, about 18 of 25 of the tubes tested in the questionable range. I emailed the seller and he said, the tubes were good, he has sold thousands to others who have re-sold them, and I was the only person who complained.

I was waiting for my 2nd box of 25, and he suggested I use another tube tester since mine may be wrong and is not very good. I recd the 2nd box of 25 and took now 50 tubes to a local electronics store and used their BK DynaJet 707, which is a machine they test all their tubes on....

Box 1---on their tester, now 20 of 25 tested "questionable"
Box 2-19 of 25 tested "questionable" on their tester.

I email the seller who now sort of alleges that even though I claim I have 20 years of tube experience, I don't sound like it. He offered a refund, less my shipping costs to and from, less my PayPal fees. I lost about $80 on the deal.

I get my refund today and read his PayPal remarks, and in bold, he claims all the tubes I sent him test NEW on his Hickok tester. for a fact, there were at least 3 which were plain DEAD on both my testers...

My question, do you think BK testers can test a tube to be bad, when in fact they are not? Does BK tube testers have issues with testing 6550s?,

I am glad to get past this situation, but really am a bit peeved at this seller, I was only telling it like it is for my perspective and 2 tube testers results.
128x128justlisten
albertporter's avatar
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albertporter
4,949 posts
 
In my experience with B&K and Hickok testers, the B&K will fail a tube that the Hickok passes as good.

My B&K was the 747, the Hickok was the 752A

I have no idea what was going on with the tubes or who the fellow was with ARC, but it's good that you got pretty much all your money back since you were dissatisfied.

As for replacements, now that your back to where you began, you should consider the SED Wing C 6550. A much better tube and available matched from the factory. I just bought 60 and had only one fail after about 100 hours.

That's about what NOS tubes did in the "good old days" of great tubes.
justlisten's avatar
justlisten OP
489 posts
 
thanks for the replies, I too agree that seeing how I got some tubes of the same lot to fall within the "good" range, this would show the B@K can pass a 6550.....but as Albert points out, he has experience that a B@K will fail what a Hickok will pass. This is what the seller said. The second tester may have been a B@K 747, I think I have a B@K 707.

I do have some used GE 6550a which I bought as "used" from anothee AGON member and those test well into the "good" range of my tester.

Again, I am just glad I cut my losses and use the tried and true tube dealers.
avguygeorge
2,300 posts
 
Just thought I'd chime in re. some EL34's;bought as NOS. The sad thing is these tubes with questionable results cost me 3x's as much, as they take out the bias resistor/s. Ya gotta be careful and think of potential damage to your amp;forget about sound quality and life of the tubes itself. Then we have some amps where a bad tube can damage much more than a bias resistor.
hirsch9000
7 posts
 
B&K testers do not "lie", per se, but very few testers tell all of the truth. The Hickok and B&K's probably use different bias voltages, different test voltages, different frequencies of the test signal, and perhaps are testing different parameters. I use a B&K 747 and Heathkit TT-1A. The Heathkit is almost certainly the more "accurate" tester, yet I use the B&K most of the time. If a tube is borderline, the B&K will often reject it, while the Heathkit might let it through. But do I want borderline tubes in my amps? Not really. I'll risk false negatives with the B&K, simply because they are less risky than false positives with the Heathkit.
dlstephenson
121 posts
 
I have gone back to KNOWN sources for tubes as almost all the tubes that I have purchased "WHOLESALE" have been questionable. But when I really think about it, how many individuals in the current market can get outstanding tubes test them and sell them cheap?
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