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FDP Forum / Amp Mods, Repairs, and Projects / A friend says an emissions tube tester will damage tubes!!!

BbendFender
Contributing Member
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American Patriot

About as ordinary as you can get.
Sep 7th, 2018 12:28 PM   Edit   Profile  

I don't agree because I've used a little Sencore emissions tube tester for years with no damage to any of my tubes. He says if you leave the setting at "Emissions" for more than a few seconds it will damage the tube. Chime in any techs.

I also have some model B&K and a Hickock testers that I occasionally use when I want to know more about the tube.

Leftee
Contributing Member
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VA

Sep 7th, 2018 04:01 PM   Edit   Profile  

I’ve not heard that before.

Ever

DrGonz78

United States Phx,AZ

Sep 8th, 2018 01:28 AM   Edit   Profile  

please ask your friend to elaborate on why he believes this to be true. You only need to run an emissions test for a few seconds to test the tube anyway. Tube testers really don't put such a strain on a tube in the first place. When you put a pair of 6L6GC with 490v or more pulling 30+ ma of current is by far more of a test to a tube than a tube tester.

willie

Too Near Atlanta GA

Amp Tech Emeritus
Sep 8th, 2018 07:59 AM   Edit   Profile  

Trying hard not to find amusement...and yes, I'd love to hear the rationale for such a belief. Tube testers put very little load and stress on a tube...maybe this guy knows something that the rest of the technician world isn't on to..could be...

w

BbendFender
Contributing Member
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American Patriot

About as ordinary as you can get.
Sep 8th, 2018 09:26 AM   Edit   Profile  

It would be very hard to win any argument with this guy. He's our local guitar tech and thinks he is the only person in the world who knows how to properly set up a guitar or work on an amp.
He gave me a bunch of hogwash but I really didn't believe it and for sure didn't argue with him.

Peegoo
Contributing Member
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Head down, ears back

Headed for the bar
Sep 8th, 2018 10:36 AM   Edit   Profile  

People are weird. They have their own version of reality.

Les Paul went to his grave claiming he designed the guitar that bears his name, when in fact it was not true at all.

I'm that way about some things, like using baking soda and CA to repair a slot in a nut. Most pros do it, thanks to super-pros like Dan Erlewine promoting it as a good repair technique.

My opinion is it's bad, because even though sodium bicarbonate crystals have a Mohs hardness of 2.5 (fairly soft), it has a PH of 9 which makes it alkaline. Add some moisture (humidity, sweat from the hands, etc.), and you have corrosion on the strings. The corrosion not only weakens the string, it also causes it to stick in the nut slot.

If someone doesn't want to spring for a new nut, I repair individual nut slots with CA and bone dust I save from previous nut jobs.

I'm probably over-thinking this (you change your strings before it becomes a real problem, right?), but it just seems wrong to use a technique that contributes to accelerated wear or damage.

Leftee
Contributing Member
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VA

Sep 8th, 2018 11:35 AM   Edit   Profile  

CA and baking soda

I have a nut on a guitar I fixed with this years ago. I will get around to replacing the nut. But it’s been fine.

Peegoo
Contributing Member
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Head down, ears back

Headed for the bar
Sep 8th, 2018 11:58 AM   Edit   Profile  

See what I mean? I'm biased by my own blindness.

+o)

Leftee
Contributing Member
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VA

Sep 8th, 2018 01:23 PM   Edit   Profile  

I’ve sniffed too much CA.

stratcowboy
Contributing Member
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USA/Taos, NM

Sep 8th, 2018 06:01 PM   Edit   Profile  

"...previous nut jobs."

Are those the customers, or the guitars?

Also...

Another great band name!

"Tonight...on the main stage. From Fruitvale, CA. Celebrated recording artists...Previous Nut Jobs!!"

pdf64

UK

Sep 11th, 2018 08:16 AM   Edit   Profile  

I think that emission testers operate by putting the 'tube under test' in diode / zero (or even positive) bias mode (ie linking the grid/s to the cathode or even plate), applying plate voltage and measuring the current it can pass.
Even just for a few seconds, that doesn't seem a great idea to me, especially with current production tubes, whose limits are anyone's guess.
I can envisage that they might well become damaged from the potentially excessive cathode current, eg see https://music-electronics-forum.com/showthread.php?t=46108

Emission testers seem kinda pointless to me.
Surely what matters is how the tube actually works in a real world circuit, not how well it holds together when operated as a diode, way beyond any normal working conditions?
It seems akin to taking a car for a test drive into a brick wall, testing something just for the sake of testing it.

External link

(This message was last edited by pdf64 at 11:38 AM, Sep 11th, 2018)

willie

Too Near Atlanta GA

Amp Tech Emeritus
Sep 11th, 2018 10:42 AM   Edit   Profile  

This is all pretty much true...however, the voltages used in emission testers are low...really quite low and don't subject the tube to much of a hard time. :) I am died in the wool mutual transconductance tester fan, but having learned the trade in an old world style TV repair shop, we used emission testers in the field (customer's homes) along with known good tubes and this was the state of the art for many years. I can also say that in well over 50 years, I can't recall ever knowingly seen or had demonstrated any damage done to a vacuum tube that had been tested on an emissions style tester. So, the technical facts stated are true and I agree with that for sure, but experience has taught me not to fear the down and dirty tests done on an emissions tester. I just wouldn't bet my life or reputation as a technician on the good/bad results of one, nor would I fear damage to a tube from a quick test on a good quality emissions tester....ymmv. :)

w

pdf64

UK

Sep 12th, 2018 06:58 AM   Edit   Profile  

Thanks willie, yes, I'm just commenting from a theoretical perspective, I have next to no experience of emission testers, and am in no hurry to change that :-)

willie

Too Near Atlanta GA

Amp Tech Emeritus
Sep 12th, 2018 08:22 AM   Edit   Profile  

LOL...perhaps wise my friend. I've had enough of that for the both of us. Carry on, you're doing great. ;)

w

rfrakes331K
Contributing Member
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IL USA

RonHalen Jokingly He Says
Sep 13th, 2018 07:30 AM   Edit   Profile  

I also have a Sencore, and have not found Emissions to be a problem. I am a Stroke Retard though sand also have a B&K tube tosser!

Silverface

Lawndale CA

No Chops but Great Tone ©
Oct 5th, 2018 12:22 PM   Edit   Profile  

He's right - in some cases.

Some testers - both Emission and transconductance - apply AC voltage to the plates and cathodes, and that CA damage some tubes. I don't recall which models as I don't use anything but a calibrated Hickok 6000A, and it only for preamp tubes and weeding out shorted power tubes.

Emission testers can only weed out bad tubes - they can't tell you how good a tube is. And transconductance testers 1) have to be calibrated every 5-10 years to be of any use at all, and 2) supply much lower plate voltages (185 max) than found in tube guitar amps, making them useless for judging quality of power tubes (or for matching them).

Since calibration runs $150-250 and very few techs even do it, it's very rare for tube sellers to own testers any good for checking preamp tubes - and unless they own a specialty high-voltage tester their power tube tests are irrelevant.

FDP Forum / Amp Mods, Repairs, and Projects / A friend says an emissions tube tester will damage tubes!!!




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