Testing el34's on my Tube tester with 6Ca7 setting

[jerryjg]

My tube tester only has 6ca7 setting, and I tested my el34's and they all tested into the questionanble range. Do I have a bunch of bad el34's, or would the tester read wrong for the el34's useing the 6ca7 test?

[tubesornothing]

Hmm, same tube.  NOS or new?  What type of tube tester and test are you doing?  If its just an emission test, then probably best to use your ears.

[jerryjg]

Hmm, same tube.  NOS or new?  What type of tube tester and test are you doing?  If its just an emission test, then probably best to use your ears.

well, I had heard one was a pentode and one was a tetrode, but I dont knwo too much about the specifiecs. Useing an old Eico 667, and just doing a emissions test. One a 6l6, itll swing to the good area ( green) for a good tube, but on all my el34's( some new, some old) they all test bad. In my traynor amp, two of the the el34's that tested bad( well, yellow range, or  'questionable"), were sounding great in the amp.
I just dont want to use a tube that might hurt my amp.
Seems like I am always ruining an amp  by useing it  with a bad tube.-  :'(

[PRR]

> Eico 667

Believe the Short Test.

Believe the emission test only if it says zero.

(But re-re-check your switch settings.)

(And re-confirm zero emission in a healthy amplifier; don't trust the EICO further than you can throw it.)

Do NOT believe the emission test Low/OK reading says ANYthing about how the tube will operate.

Anyway, low emission will NOT hurt your amplifier.

In a TV set, low emission might explain why the screen is shrunken.

In a LOW-voltage amplifier (such as transformerless radios), low emission might explain why you can't meet your 1.3 Watt output spec.

Most high-voltage audio tube applications do NOT need ALL the emission of the tube.

Even if the EICO were reading emission correctly.

[FYL]

would the tester read wrong for the el34's useing the 6ca7 test?

The 667 can't properly measure the emission of medium or large power tubes because of it's architecture and power supply limitations. Max voltages are: plate 180V, screen 90V, while specs give Ua 250V, Us 250V, Ug -12.2V for 100 mA current.

No wonder that new EL34's read in the 85 to 95 range on it's 0 to 140 emission scale...

[jerryjg]

Thanks everyone for your kind assistance. I guess what i really can't quite grasp is why a 6l6 ould swing wide into the Green, or excellent emissions range, when none of the el34's would do it? Is it some type of difefrence in the power of the tube emissons between the EL34/6Ca7 and the 6L6? Thanks again.

[PRR]

The 667's test conditions are nothing like "normal operation".

After too-tedious research, this is how it "tests" a 6CA7/EL34:

Plate = 180V
Screen = 90V
Grid = plus 14V
"Meter 100" = 45mA

The way-too-low screen voltage, and the abnormal positive grid voltage, put this condition way outside the maker's specifications or intentions.

FWIW, this is what it "tests" a 6L6 at:

Plate = 180V
Screen = 90V
Grid = plus 25V
"Meter 100" = 45mA

They must have got the original "OK" numbers simply by testing tubes; there is NO published data for EL34 with positive grid (and not much for 6L6, unless you pretend that 807 is the same). But these conditions being outside published specifications, the makers are free to change the tubes while keeping the in-spec performance similar, even if it causes great change in out-of-spec performance.

I would suspect the positive grid voltage, with low screen voltage, is stealing current away from the plate and into grid or screen. And that tubes are not made exactly the same from 1960 to 2009. The grid winding may have been modified for better performance/cost at normal conditions, which might also make it a better current-stealer in ab-normal conditions.

But in any case, an emission test is NOT a good test for a tube. At best, it may weed-out some dead-shorts and some total duds. But the "merit" indication was bogus at best, and more bogus when tube detailing changes characteristics in the abnormal zones.

> My tube tester only has 6ca7 setting, and I tested my el34's ...  an old Eico 667

EICO released many revised setting-charts to registered owners. You didn't subscribe? Then get this one:
ftp://bama.sbc.edu/downloads/eico/667(2)/
Yes, it is a verrrrry slow download, may refuse you a few times, but you need it.

[jerryjg]

The 667's test conditions are nothing like "normal operation".

After too-tedious research, this is how it "tests" a 6CA7/EL34:

Plate = 180V
Screen = 90V
Grid = plus 14V
"Meter 100" = 45mA

The way-too-low screen voltage, and the abnormal positive grid voltage, put this condition way outside the maker's specifications or intentions.

FWIW, this is what it "tests" a 6L6 at:

Plate = 180V
Screen = 90V
Grid = plus 25V
"Meter 100" = 45mA

They must have got the original "OK" numbers simply by testing tubes; there is NO published data for EL34 with positive grid (and not much for 6L6, unless you pretend that 807 is the same). But these conditions being outside published specifications, the makers are free to change the tubes while keeping the in-spec performance similar, even if it causes great change in out-of-spec performance.

I would suspect the positive grid voltage, with low screen voltage, is stealing current away from the plate and into grid or screen. And that tubes are not made exactly the same from 1960 to 2009. The grid winding may have been modified for better performance/cost at normal conditions, which might also make it a better current-stealer in ab-normal conditions.

But in any case, an emission test is NOT a good test for a tube. At best, it may weed-out some dead-shorts and some total duds. But the "merit" indication was bogus at best, and more bogus when tube detailing changes characteristics in the abnormal zones.

> My tube tester only has 6ca7 setting, and I tested my el34's ...  an old Eico 667

EICO released many revised setting-charts to registered owners. You didn't subscribe? Then get this one:
ftp://bama.sbc.edu/downloads/eico/667(2)/
Yes, it is a verrrrry slow download, may refuse you a few times, but you need it.

Brilliant, andI very much appreciate your efforts to explain this . I'm in way over my head here , but i get the jist of it. Again, thanks very much.

[FYL]

EICO released many revised setting-charts to registered owners. You didn't subscribe? Then get this one:
ftp://bama.sbc.edu/downloads/eico/667(2)/
Yes, it is a verrrrry slow download, may refuse you a few times, but you need it.

Eico is well known for the numerous errors in the charts and settings.
Even the last version (7511) published by Coletronics for Eico is full of crap.

Bama is a royal pain in the neck, use the mirror at Edebris
http://bama.edebris.com/manuals/

I've uploaded a clean pdf copy of the 7511, it'll be available for the next 96 hours or so:
http://www.aingeal.com/misc/Eico%20667%20Master%20Setting%20Chart.pdf

(Warning: 4.5M file)

File removed.

[Tiny_Daddy]

I notice my Knight emissions tester uses the same settings for 6L6 and 6CA7. But it hasn't been much use for testing power tubes. What would be better is a built-in amp and speaker, or maybe just an audio output jack for listening to noisy tubes.

[FYL]

What would be better is a built-in amp and speaker, or maybe just an audio output jack for listening to noisy tubes.

Building a small real-world matcher/tester is quite easy.
Have a look at http://priceamp.home.comcast.net/~priceamp/tubematcher.htm

You may add two variable supplies (a Mosfet and a few components), an input jack and switch (in order to use a signal generator if you want to measure Gm), an output switch, a small OT with it's glue, you then would have a complete tester/matcher for known functional power tubes (they should be tested first for shorts, leaks and gas, something a basic tester such as the Eico 667 does really well).

[gldtp99]

Wow--- thanks for all the info about the Eico 667---- my 667 is the only tube tester i have (other than real amps)----i understood that it wasn't the greatest tester because it tests emissions only, besides being old---- but i didn't realize just how limited it is.
Maybe it's time for an upgrade...............gldtp99

[FYL]

but i didn't realize just how limited it is.

it's one of the best testers for pre-qualification as it allows to measure very precisely inter-electrode leaks, most others use a Good/Bad system trigered between 2 and 20 Mohms - OK for gas or grid emission but giving false alerts for inter-electrode resistance. A power tube with, say, 1 Meg between heater and cathode is OK but most consumer grade testers will show it as defective.

[EL34]

here's some more info on home tube testing.

http://www.el34world.com/Forum/index.php?topic=6595.0

[Rich]

More on using the EICO machine;
http://tone-lizard.com/Eico666.html

Tube tester write up;
http://tone-lizard.com/Tube_Testers.html