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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 9:57 pm
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Ok. That's interesting, but what exactly does "strength" and the cathode current represent. Gm I understand. But what does a "strength" of "120%" mean? Is the measured cathode current some sort of maximum current flow at the set plate voltage?

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Post subject: Re: cryo treated tubes
Posted: Sun Jan 13, 2013 10:40 pm
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The strength is how well the tube conducts, or how high the transconductance (Gm) is at the specific applied voltages. The number is more for comparison than anything else, and shows a "good" or "bad" range on the scale, the lower the number, the weaker the tube is. Notice that at about 80%, the scale starts to get into the "bad" range, indicating a weak tube. The Cathode current is just that, how much current flows with X amount of voltage on the Plate, screen and grid. In the case of 160 volts on the Plate, and 100 mA of Cathode current, as you know this is about 16 watts dissipated by the tube, and the percentage of conductance shows that this is a strong tube at a decent operating wattage. The numbers will be proportional to the higher voltages that might be applied in an amp. So, for example, I could increase the Plate voltage and decrease the grid voltage proportionally and still have the same amount of current flowing through the tube. Increase the Plate voltage and/or increase the screen voltage with the same grid voltage, the Cathode current should increase. Increasing the grid voltage at the same Plate voltage results in more Cathode current, and etc.

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Post subject: Re: cryo treated tubes
Posted: Mon Jan 14, 2013 3:56 pm
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Ah, thanks. That helps.

I looked on E-Bay and could not find any working Eico 667s. :(

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Post subject: Re: cryo treated tubes
Posted: Mon Jan 14, 2013 10:56 pm
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Yeah, I had to look for quite awhile, got outbid on a couple, and finally found one in great shape with manuals and put in a high max bid and won. Keep looking, you'll find one. In the mean time, this is just about the best site that I've found for info about tube testers (link below). Lots of links to click for more specific info on different types of testers. You might even find a different model, such as the Jackson 648x, that might work well for you. The Eico 666 might be good enough also, and tests older small tubes that the 667 doesn't have sockets for (4, 5, and 6 pin). I went with the 667 mainly because it has a 12 pin tube capability (the 666 only has 9), but I'm not sure why I would need that, but I felt that the 667 was a little more modern and I didn't have much need to test the older 4, 5, and 6 pin tubes. The Eico 666 and 667 are nearly the same otherwise.

http://www.tone-lizard.com/Tube_Testers.html

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Post subject: Re: cryo treated tubes
Posted: Tue Jan 15, 2013 3:44 pm
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Thanks.

Yeah, I have the Tone Lizard site bookmarked.

Not sure I want something with "666" on it in my house. Although the middle numbers in my social are "666". That might explain a few things about me. :lol: :lol: :lol:

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Post subject: Re: cryo treated tubes
Posted: Tue Jan 15, 2013 10:13 pm
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:lol:

I think that was part of it for me to, so I had to go with the 667. Weird about your SS#. If I add the numbers in each section of mine, I get 6-6-5. Whew! The guy born right after me is probably the anti-Christ. :shock:

:lol:

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Post subject: Re: cryo treated tubes
Posted: Tue Jan 15, 2013 10:17 pm
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shimmilou wrote:
:lol:

I think that was part of it for me to, so I had to go with the 667. Weird about your SS#. If I add the numbers in each section of mine, I get 6-6-5. Whew! The guy born right after me is probably the anti-Christ. :shock:

:lol:


Ummm. I was born 4/2/54. When were you born?

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Post subject: Re: cryo treated tubes
Posted: Tue Jan 15, 2013 10:33 pm
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6/10/63 I think that you are safe!

Just spotted these!

This one seems to be in great shape. You might want to put a max bid of at least $230 to make sure that you get it. I have seen them go from between $150 and $200 in this condition. My max bid was $200+ and I got mine for $177.
http://www.ebay.com/itm/ESTATE-VINTAGE-EICO-667-TUBE-TESTER-DYNAMIC-CONDUCTANCE-TUBE-TRANSISTOR-TESTER-/130835776754?pt=LH_DefaultDomain_0&hash=item1e766b84f2

This one needs repair, not sure if you are into repairing it yourself or not.
http://www.ebay.com/itm/EICO-667-DYNAMIC-CONDUCTANCE-TUBE-TESTER-WORKS-BUT-NEEDS-MINOR-REPAIRS-READ-DESC-/121052675940?pt=LH_DefaultDomain_0&hash=item1c2f4d3f64

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Post subject: Re: cryo treated tubes
Posted: Tue Jan 15, 2013 10:38 pm
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Whew! :lol:

Gonna have to wait on a tube tester for awhile. The new amp kit was $500 and I haven't ordered tubes yet.

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