Tested Tubes anyone?

[Ki Choi]

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print vacuum tubes GE 5814 TESTED GOOD - $105 (Marysville)






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3 GE 5814 tubes.
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All three tubes have sever bent pins syndrome. I wonder how he was able to plug them into a tube tester to test these tubes to be GOOD... So much I don't know...

[mep]

You had me for a second because I thought you were selling these junk tubes. I was going to ask you about the bent pins.. I wouldn't give $.01 for all 3 of them.

[MylesBAstor]

Tested for what?

[Ki Choi]

Tested for what?

They are tubes and not sticks.

[Ki Choi]

This ad is an example of recent gold rush or tube rush where people dig out old and replaced tubes from TV repair shops and list them on Craigslist. I saw one well used Telefunken 12AX7 for sale at $150 recently. At this point, it's the buyers of these tubes are stupid as much as the silly sellers.

[microstrip]

Even if tested, buying tubes from unknown sources is a lottery game. A tube can be approaching the end of its lifetime and still measure good.

Tubes wear mostly because of cathode evaporation - the key point for tube life. Sometimes they become noisy because material emitted from the cathodes deposits on the grids and they start emitting electrons - such tube will measure perfectly in conventional meters.

Long ago - I was still a student at the University - I read an interesting article written the British Post Office engineers where they described techniques to determine the remaining of life in a tube. Unfortunately I did not keep a copy and could not find it since them. But as far as I remember it involved making measurements in a tube at lower filament voltages and comparing them to those of reference tube. At that time (post WW II years) wear of tubes was a particular concern of the telecommunications - tubes were scarce and they could not afford to replace them systematically, but they wanted to minimize maintenance visits and downtime periods.

[mep]

Francisco- Sounds like you are describing a cathode life test like the Better Hickok testers will perform. Basically it drops the cathode voltage and measures how much the cathode emission drops off.

[MylesBAstor]

Even if tested, buying tubes from unknown sources is a lottery game. A tube can be approaching the end of its lifetime and still measure good.

Tubes wear mostly because of cathode evaporation - the key point for tube life. Sometimes they become noisy because material emitted from the cathodes deposits on the grids and they start emitting electrons - such tube will measure perfectly in conventional meters.

Long ago - I was still a student at the University - I read an interesting article written the British Post Office engineers where they described techniques to determine the remaining of life in a tube. Unfortunately I did not keep a copy and could not find it since them. But as far as I remember it involved making measurements in a tube at lower filament voltages and comparing them to those of reference tube. At that time (post WW II years) wear of tubes was a particular concern of the telecommunications - tubes were scarce and they could not afford to replace them systematically, but they wanted to minimize maintenance visits and downtime periods.

One of the biggest issues IMHO. And you have tubes that measure good even on an amplitrex (or my George Kaye tester). Put them in the equipment and the tubes sound pretty but have no dynamics.

[c1ferrari]

One of the biggest issues IMHO. And you have tubes that measure good even on an amplitrex (or my George Kaye tester). Put them in the equipment and the tubes sound pretty but have no dynamics.

Myles, do have access to a curve tracer? I'm wondering if those tubes which show well on an Amplitrex or Kaye tester would also acquit themselves well on a CT

Vbr,

Sam

[MylesBAstor]

Myles, do have access to a curve tracer? I'm wondering if those tubes which show well on an Amplitrex or Kaye tester would also acquit themselves well on a CT

Vbr,

Sam

Good question. Not any more.

What I like most about George's machine is the tubes are actually tested for performance in a real audio circuit. But only small signal tubes.

The microphonics portion of the tester is handy too! Interesting how you can hear how one of two triode sections is microphonic. There worst in my experience were the Ei ECC83s. I can't imagine what cj went through to get quiet and working phono tubes when they used the Eis in their phono sections.

[microstrip]

Myles, do have access to a curve tracer? I'm wondering if those tubes which show well on an Amplitrex or Kaye tester would also acquit themselves well on a CT

Vbr,

Sam

Unfortunately the curves will show the same. Most people will be disappointed to know that their beloved Telefunken's tracer curves are similar to those of cheap brands ...

[MylesBAstor]

Unfortunately the curves will show the same. Most people will be disappointed to know that their beloved Telefunken's tracer curves are similar to those of cheap brands ...

I think that companies like cj, ARC, VTL, etc. realize that the only way to really see how a tube performs is putting it in the actual circuit and does that performance meet specs.

[microstrip]

I think that companies like cj, ARC, VTL, etc. realize that the only way to really see how a tube performs is putting it in the actual circuit and does that performance meet specs.

ARC uses mostly the 6H30 double triode tube. As my system at a certain moment used 25 of them I built a jig connected to my PC to test them in a circuit with their typical operation points in the real circuit, measuring even distortion and noise. I used it mostly to match and select them. The 6h30 is known to lasts for a long time - ARC tells us to replace them at 4000 hours. Most of my tubes still measured perfect at 5000 hours, but when I replaced them the equipment sounded much better with the new fresh tubes.

BTW, the effects of burn-in are notorious in tubes - in many tubes the noise spectra changed significantly during the first 100 hours.

[MylesBAstor]

ARC uses mostly the 6H30 double triode tube. As my system at a certain moment used 25 of them I built a jig connected to my PC to test them in a circuit with their typical operation points in the real circuit, measuring even distortion and noise. I used it mostly to match and select them. The 6h30 is known to lasts for a long time - ARC tells us to replace them at 4000 hours. Most of my tubes still measured perfect at 5000 hours, but when I replaced them the equipment sounded much better with the new fresh tubes.

BTW, the effects of burn-in are notorious in tubes - in many tubes the noise spectra changed significantly during the first 100 hours.

Funny thing about the 6H30s. The 6H30-EBs (2012 or so?) that cj initially supplied with the ART were junk. They didn't last at all. I've gone to using the NOS pre-76 6H30-DRs and besides being better sounding, they have had zero problems.

[c1ferrari]

The microphonics portion of the tester is handy too! Interesting how you can hear how one of two triode sections is microphonic.

Yeah, that's a real bummer when one side is microphonic and everything else is alright.

[MylesBAstor]

Gotta love that sleigh bell sound!

[c1ferrari]

Unfortunately the curves will show the same. Most people will be disappointed to know that their beloved Telefunken's tracer curves are similar to those of cheap brands ...

I'm elated when tubes of various manufacture mimic the Receiving Tube Manual...it's my baseline for electrical -- read NOT sonic -- performance.