Testing Vacuum tubes not sure where to post?

[jtrouter]

Hello all!
As the title says im not sure where to post this but here goes. I have a question about testing vacuum tubes? SO a 6LQ6 tube normally
seems to come in boxes labeled a 6LQ6/6MJ6/6JE6C, Now i have a bunch of these but when i go to test them what tube data do i test
under? All 3 of these tube numbers have testing parameters that are different, And depending on which parameters or settings i use the
results can range from a bad tube to a good tube? So if i test as a 6lq6 it can show bad but it i test as a 6je6c the tube is showing strong?
I sure would like to be able to know if the tubes that i buy are good and on the same hand if i choose to sell them i would like to be able
to make sure they are good. Does anyone know how to test tubes that have more than a single part number on them.
Thank you for all ideas.

 

[nomadradio]

The original type number from the early 1960s was the 6JE6. Was used as the horizontal deflection (sweep) amplifier for color TVs with round tubes. Rectangular color CRTs came along a couple of years later. As the production expanded, it got upgraded. A suffix letter would indicate this, starting with "A", then "B".

It got upgraded in the late 60s, called (at the time) 6LQ6. Had thicker glass and other toughness features. A black plate cap, rather than a shiny plated one reveals this version.

Later, the upgraded tube got renumbered to 6MJ6. The original 6JE6 now got the suffix letter "C", as if the older type tube would actually perform like the (now) upgraded 6MJ6. At least they gave the tougher tube its own type number.

As far as a tube tester can tell, these are all the same tube. The differences between them have mostly to do with how they behave at full peak circuit current.

A tube tester won't put but a tiny test current through a tube. As such, all the 6JE6/6LQ6/6MJ6 types are the same with only that tiny test current flowing.

A tester can tell you only so much about "how" good a tube is. Mostly we depend on a tester to find damaged and failed tubes that will cause problems in the customer's equipment.

If the tester says it's bad, the tube probably is. If it says the tube is good, it might be.

73

 

[jtrouter]

The original type number from the early 1960s was the 6JE6. Was used as the horizontal deflection (sweep) amplifier for color TVs with round tubes. Rectangular color CRTs came along a couple of years later. As the production expanded, it got upgraded. A suffix letter would indicate this, starting with "A", then "B".

It got upgraded in the late 60s, called (at the time) 6LQ6. Had thicker glass and other toughness features. A black plate cap, rather than a shiny plated one reveals this version.

Later, the upgraded tube got renumbered to 6MJ6. The original 6JE6 now got the suffix letter "C", as if the older type tube would actually perform like the (now) upgraded 6MJ6. At least they gave the tougher tube its own type number.

As far as a tube tester can tell, these are all the same tube. The differences between them have mostly to do with how they behave at full peak circuit current.

A tube tester won't put but a tiny test current through a tube. As such, all the 6JE6/6LQ6/6MJ6 types are the same with only that tiny test current flowing.

A tester can tell you only so much about "how" good a tube is. Mostly we depend on a tester to find damaged and failed tubes that will cause problems in the customer's equipment.

If the tester says it's bad, the tube probably is. If it says the tube is good, it might be.

I have read this before about bad is bad and good maybe ok. So does that really mean if i test say 4 tubes and 3 show 95% and 1 shows 70% then i should assume them to be at least close to the same? Everything i have read says they should be closely matched based testing score then my manufacturer.I do know that then brand id on the tube does not mean that it belongs to the true manufacturer. But i have read that in rf amplifiers the tubes should be matched together, so how do i find close matching tubes to each other?

 

[walterjn]

I haven't really had the opportunity to play with many tube amps, as most of the time I have only really had mobile setups. That said, I personally would consider anything that a tester says is 90-95% good to be matched. The smaller the percentage difference the better. The 3 at 95% would be matched almost perfectly in my opinion, and the 70% is far enough off that I'd be hunting another that tests closer to 90-93%.
I'm sure that there are those who will have a better answer, and will chime in shortly.

 

[nomadradio]

One weak tube in parallel with three strong ones is not so large a risk.

But one strong tube in parallel with three weaker tubes is usually a bad idea. The strongest tube will draw the most current. Causes it to take more than just its one-fourth share of the load and run hot.

But not for long.

73

 

[Rwb]

when you all post bout tube testing,i think back when i was a kid. the grocery store we used was big.
in the back end of the store was a big red RCA table and on the back you matched your tube n plugged it in,flip a switch n it tested your tube. remove tube raise top and boxes of new tubes indexed.
hope im not boring ya by now
anyhow i had a huge trutone am sw radio when i was 5. i had a wire ran out across trees to radio. 1 day it quit so i removed every tube .we went for grocerys n i had my tubes. store employee held me up n helped me test every tube. 1 was bad 2 were weak. we got the 3 out n when i got home i installed em n wow it worked.
seems like those tubes cost about $4.25 for the 3 back in 1960