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 tester doubt and last minute panic

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Tubetechie105



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PostSubject: tester doubt and last minute panic   Sun Oct 17, 2010 11:13 am

OK, after rereading the "idiots guide to tubes testers" on a whim, something very worrying occurred to me: is an Eico 666/667 a Mutual conductance tester or a emissions tester? I thought those testers( along with the Simpson 1000) where the Gm type?
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eppeder



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PostSubject: Re: tester doubt and last minute panic   Sun Oct 17, 2010 1:18 pm

Hi,
I believe the Eico is an emissions tester. You can also go to alltubetesters.com (I don't know how to put the link here. This is Roger Kennedy's site and he has a page on tube testers that he recommends. There are guidelines there also for the type of tester and what you want it to do.
Unfortunately, I didn't find it until after I had bought several of these. The good news is I picked up a Hickok TV2 for $200, way less than I paid for a Knight KG600C. Funny thing about that learning curve that's always involved..........
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Mike C.



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Location : Central NH

PostSubject: Re: tester doubt and last minute panic   Mon Oct 18, 2010 2:34 pm

You could go one small step further and call an Eico 666/667 a dynamic tester,which is what they are known as.They are slightly more advanced than a basic emission tester in that they do not test every tube as a diode,they apply AC voltages to the individual tube elements and measure the resulting plate current.They are definately not Gm testers.
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dberman51



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PostSubject: Re: tester doubt and last minute panic   Mon Oct 18, 2010 8:53 pm

IIRC what you described is transconductance. So why would that not be a transconductance tester?

-David
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Sal Brisindi



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PostSubject: Re: tester doubt and last minute panic   Mon Oct 18, 2010 10:02 pm

I have the Eico 667 (amongst 20 or so other tube testers) and I always thought the 667 was better than a emissions tester but not as good as a gm tester.

I very rarely use it though.

Sal

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Mike C.



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 6:37 am

dberman51 wrote:
IIRC what you described is transconductance. So why would that not be a transconductance tester?

-David

I guess you could call it anything you like.The point is,it's not a Gm tester,which is basically what the OP wanted to know.
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gvel

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Location : Howell, MI

PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 10:46 am

No, it's not a gm tester. Eico called it something misleading, though. Something like "dynamic conductance"? I once read somewhere, on the net, these testers indicate the AC voltage gain, of the tube in test.

Google is your friend! There is a lot of Eico info!

If I was home, I could fill you in better. The 667 is my only tester! Too bad my brain doesn't function like it once did!



Last edited by gvel on Tue Oct 19, 2010 4:35 pm; edited 1 time in total
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dberman51



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 12:13 pm

Mike C. wrote:


I guess you could call it anything you like.The point is,it's not a Gm tester,which is basically what the OP wanted to know.
It is testing the tube on the basis of Gm, so it is a Gm tester, in fact. What is does not do is indicate the quality of the tube directly in umhos, the metric for Gm. Some of these types of testers, including my Superior TV-12, give you the formula to calculate the actual Gm from the control setting and meter reading if you wish to do so. I'm not familiar with the Eico tester specifically, but from the description given in a previous post it seems to fall into the same category as the Superior TV-12, therefore a transconductance tester.

-David
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Alan Douglas



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 12:47 pm

Nope, it can't test Gm with positive grid bias, which is what it uses.

The Superior TV-12, as far as I know, is also a dynamic emission tester, like the Eico 666/667, Jacksons, and Precisions.

Simple emission testers apply an AC voltage to all grids and plate, relative to the cathode, and meter the resulting current (only half of the AC cycle is used). "Dynamic" emission testers apply proportional AC voltages to the various grids and plate, and measure only the plate current. But the tube is biased "full on" in either case, so they measure total emission.

Gm testers apply negative grid bias and an AC signal, and measure the amplified AC signal at the plate, but not the DC plate current. There are many ways of accomplishing that, but Hickok's method was cheapest, and dominated the field as long as the patent ran.
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Tubetechie105



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 2:16 pm

Mike C. wrote:
dberman51 wrote:
IIRC what you described is transconductance. So why would that not be a transconductance tester?

-David

I guess you could call it anything you like.The point is,it's not a Gm tester,which is basically what the OP wanted to know.
well yes you can say that, the REASON I asked that is I have met a few Incredibly talented members(wcirco,DX, lineman duke....) and many other members keep saying that anything short of Gm tester is, paraphrased, "crap" . Now I have a limited budget( read: I can't get way with paying a $1000 on a single tester) and No one here has a spare Hickok or heathkit TT1A that they want to sell tat I have found as of yet. Believe me I have been begging and pleading( and still willing to pay good money for a good tester!) with this forum for sometime to get a Gm tester that has range.why do I want a tester that can test a 01A to compactrons? simple: I love to Homebrew. I use whatever I can get my hands on and build.I haven't posted anything on ARF for the simple reason I can't figure out how to post pictures here correctly.
I have a Signal generator that refuses to give a clear, music blotting unmodulated signal on anything but FM ( for the record it is an Eico 324). and the tubes test OK on what I have(precision 10-12)but that isn't enough to prove that the circuit isn't faulty.

Bottom line here: unless some wonderful, merciful member here can help me out with a Gm tester I needed to know if the Eico667 was as good as the author of the " idiots guide to tube testers" site claimed. as always my Email is labrat4028@yahoo.com if anyone wants to help/ advise
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easyrider8



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 2:56 pm

Mike C

I have been repairing test equipment for longer than I want to remember. I have Hickoks, Tripletts, Superiors, AVO, Sencore, and many more in my shop. Although I have testers with all the bells and whistles the one that sits on my bench and I use the most is a Heathkit IT-21, it will test the old tubes and the new ones and will tell you what you want to know 98% of the time. There are many good non-gm testers out there so don't think you have to have a GM tester. The only time I use a GM tester is when I am selling high buck tubes on ebay, or have a problem tube that I don't have a sub for.

Dave
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pixellany



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 3:27 pm

Just to clarify (and support) what has already been said: Gm (technically lowercase g, subscript m) is one of what is typically called the "small signal" parameters. Gm is defined as the change in plate current for a given change in grid voltage for small signals. "small signals" means that the DC parameters are not changing while the measurement is being made.
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Tubetechie105



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 5:50 pm

well to anyone still reading this: how hard would it be to locate a Hickok 800A? is that a common or rare tester?
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BlueFlame



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 6:07 pm

I see 800s on ebay on a pretty regular basis. Not as common as the 600 series, but I would not call them rare.
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Alan Douglas



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 6:17 pm

Quote :
many other members keep saying that anything short of Gm tester is, paraphrased, "crap"

Well they're wrong. Dave gave you a 98% figure; I'd say more like 90% for radio work, but the principle applies.
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frankpe



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 6:30 pm

I have a Precision 10-12, a recent Hickok 6000 and a friend with a Hickok 539c. The Hickoks are very nice but the 10-12 does the job for me 99% of the time, and it cost much less.


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Tubetechie105



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 6:39 pm

Alan Douglas wrote:
Quote :
many other members keep saying that anything short of Gm tester is, paraphrased, "crap"

Well they're wrong. Dave gave you a 98% figure; I'd say more like 90% for radio work, but the principle applies.
Alan you just made my day. I really mean it you just made me smile wider than a mule eating briers.glad I actually Bought that eico 667 now. Thank you one and all.
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easyrider8



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 8:01 pm

Good choice, now when you get it we will tell you how to get the whiskers out of the calibration pots.

Dave
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Tubetechie105



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PostSubject: Re: tester doubt and last minute panic   Tue Oct 19, 2010 8:10 pm

easyrider8 wrote:
Good choice, now when you get it we will tell you how to get the whiskers out of the calibration pots.

Dave
Whiskers? ....Why don't I just replace the( lemme see here) the 100K pots? I assume it is a wire wound linear one? as for calibration would a 6L6 reference tube( usually for Hickoks) be needed?
Can anyone send me a PDF of the construction manual? labrat4028@yahoo.com if you need my email
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Alan Douglas



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PostSubject: Re: tester doubt and last minute panic   Wed Oct 20, 2010 10:32 am

No need to replace them, just check for shorts from the wiper to ground.
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