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  #16  
Old 02-13-2014, 12:22 AM
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Tubejunke Tubejunke is offline
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Quote:
Originally Posted by miniman82 View Post
My Eico 625 does 6CA7's, and a lot of other funky tubes too. Pretty sure it came out in the late 50's, so your tester much be a lot older I'm guessing? Perhaps the manual of your unit says something similar?
I didn't even think about subs. If the 6CA7 is an older sub for an EL-34, then I could just use those settings for a test. I know that amp tubes like the EL-34 aren't new news by any stretch. However, the part # doesn't go back as far as a lot of, probably most of, the vintage scrolls provide data for. Out of the 4 or 5 testers that I have, I am sure that more than one will do the 6CA7.

Heck, although I do play guitar and have one tube amp, I don't expect to be worried about any EL-34s soon if ever. My Epiphone is circa late 50s. No octals; just miniatures.
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  #17  
Old 02-13-2014, 09:57 AM
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maxhifi maxhifi is offline
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Quote:
Originally Posted by Tubejunke View Post
I didn't even think about subs. If the 6CA7 is an older sub for an EL-34, then I could just use those settings for a test. I know that amp tubes like the EL-34 aren't new news by any stretch. However, the part # doesn't go back as far as a lot of, probably most of, the vintage scrolls provide data for. Out of the 4 or 5 testers that I have, I am sure that more than one will do the 6CA7.

Heck, although I do play guitar and have one tube amp, I don't expect to be worried about any EL-34s soon if ever. My Epiphone is circa late 50s. No octals; just miniatures.
European tube designations start with letters, American ones start with numbers. E is a 6 volt filament L is a power pentode, and 34 is the sequential number. 6 is a 6 volt filament CA is the sequential desinator, and 7 means 7 elements inside the tube, i.e. a pentode. The reason it is 7 for a 6CA7 is the supressor grid is brought out as a separate element, unlike the 6L6 where the beam forming plates are internally connected to the cathode.

All that said, when the EL34 was introduced in North America, in the 1950s, it was called the 6CA7, under the American naming convention. It's exactly the same tube, just under an American title. Other examples exist, for example

EL84 = 6BQ5
ECC83 = 12AX7
GZ34 = 5AR4

And on and on and on All are european tubes with American designations, probably to make them easier to sell and categorize in existing US inventory systems at the time.
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  #18  
Old 02-22-2014, 11:55 PM
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AUdubon5425 AUdubon5425 is offline
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I never used to test tubes until I got bit in the butt by a shorted tube burning up something a couple of times. Nothing like watching your work go up in smoke. If I have something that hasn't been run in the recent past I test the tubes, not really for emissions but for shorts.
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  #19  
Old 03-06-2014, 03:01 PM
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toxcrusadr toxcrusadr is offline
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Yep, shorts and gas are handy tests to have. I suspect that back in the day, when tubes were plentiful and there was not a finite and ever shrinking supply like there is today, that it was easy to test em and replace if weak. Like replacing your tires when they still have a little tread left. If there were no more tires being made we wouldn't toss them until they were unrepairably flat. If a service shop was working on a radio or TV, they'd replace weak or bad ones.

This probably explains why there are boxes of old used tubes in attics and basements that still test weak or good.
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