Hi Perry,
Thank you.
I got the message and replied. The answer was no, because emission testers are not that useful. They tend to sell for far more than their true value. Testers like a Hickok, Military TV series or the Stark 9-66 are "Dynamic Transconductance" type units and are far more useful. The best test is to sub a known good tube into the circuit. Never forget that you can use the circuit itself to test the tube. Measure the voltages and don't get a shock!
I'll also move this thread now.
-Chris
Thank you.
I got the message and replied. The answer was no, because emission testers are not that useful. They tend to sell for far more than their true value. Testers like a Hickok, Military TV series or the Stark 9-66 are "Dynamic Transconductance" type units and are far more useful. The best test is to sub a known good tube into the circuit. Never forget that you can use the circuit itself to test the tube. Measure the voltages and don't get a shock!
I'll also move this thread now.
-Chris
An emission tester is useful for finding shorts and worn-out tubes. It tests every tube as a diode, so it's testing the cathode only. A transconductance tester does a true functional test, though its readings may have only SLIGHT correlation with any particular circuit.
I think either would be fine for sorting used tubes and initial checkout of a radio. But performance and voltages in circuit are the TRUE tests.
Most of the time, emission testers sell for more than they're worth, and transconductance testers sell for MUCH more than they're worth...
I think either would be fine for sorting used tubes and initial checkout of a radio. But performance and voltages in circuit are the TRUE tests.
Most of the time, emission testers sell for more than they're worth, and transconductance testers sell for MUCH more than they're worth...
Hi Tom,
An emission tester will not tell you if the tube will amplify. It does not indicate cathode emission "hot spots". I'll take my 9-66 over an emission tester any day as it has also got a noise test. I have found some funky tubes with it.
I think you will agree that substitution is the best method.
-Chris
An emission tester will not tell you if the tube will amplify. It does not indicate cathode emission "hot spots". I'll take my 9-66 over an emission tester any day as it has also got a noise test. I have found some funky tubes with it.
I think you will agree that substitution is the best method.
-Chris
Hi Steve,
Amazon is a great source for Morgan's books and normally you can get a break on them. No rush as they are in production.
All,
I had replied to Steve via email that he should pick up "RDH4" and also two books written by Morgan Jones entitled "Valve Amplifiers" (VA) and also "Building Valve Amplifiers" (BVA). I own both and highly recommend them. Light math and great, easy to understand explanations. Morgan gets into some advanced concepts, the math can be found if you hunt for it.
Of course there are tons of other great texts on this subject. Even RDH3 has things to offer that did not show up in RDH4. Too many books to list really. You can download some, but I'd rather read the book in my hand.
Anyone else have trouble reading technical stuff from a computer screen? I have trouble with this.
-Chris
Amazon is a great source for Morgan's books and normally you can get a break on them. No rush as they are in production.
All,
I had replied to Steve via email that he should pick up "RDH4" and also two books written by Morgan Jones entitled "Valve Amplifiers" (VA) and also "Building Valve Amplifiers" (BVA). I own both and highly recommend them. Light math and great, easy to understand explanations. Morgan gets into some advanced concepts, the math can be found if you hunt for it.
Of course there are tons of other great texts on this subject. Even RDH3 has things to offer that did not show up in RDH4. Too many books to list really. You can download some, but I'd rather read the book in my hand.
Anyone else have trouble reading technical stuff from a computer screen? I have trouble with this.
-Chris
To be fair, testers like the Sencore "Mighty-Mites" mentioned here, WILL also find shorted tubes. In fact, they're my GO-TO for quickly finding shorts (and we have a TV-7A/U as well!). The short test on the Sencores not only tells you there's a short- it can specify WHICH PINS are shorted, as a normal part of the test (ie, you don't have to jump through hoops or hurdles flipping a bunch of switches, like you do with other testers)! This can help in finding DIFFERENT VERSIONS of tubes or determining improperly-labeled substitutes- knowing which pins are wired together (intentional short, in essence) can be a BIG CLUE in finding out what a tube ACTUALLY IS, in the case of fakes and bad substitutes.
Also, you can also find out tubes that are "tired out" by doing a cathode-sensitivity test... the Mighty-Mite manual says to turn down the filament voltage one notch, and watch the emission for drop-offs. I've spotted MANY marginally bad tubes that way. For this, it's much faster than firing up the TV-7A/U, for garden-variety issues (as in "does this tube work at all or not?").
Regards,
Gordon.
Also, you can also find out tubes that are "tired out" by doing a cathode-sensitivity test... the Mighty-Mite manual says to turn down the filament voltage one notch, and watch the emission for drop-offs. I've spotted MANY marginally bad tubes that way. For this, it's much faster than firing up the TV-7A/U, for garden-variety issues (as in "does this tube work at all or not?").
Regards,
Gordon.
Hi Gordon,
Problem is, some tubes normally show shorts between one set of elements. You need to know which ones. That and most testers use a heater voltage drop to check "life". My 9-66 does as well.
Seems to me that the fastest test is to try another tube, or measure the circuit voltages. If you were to leave your TV-7A/U out on the bench, it would be as easy to test using that. Both types require a bunch of settings and there is a "good/bad" or "English" scale on yours too.
I also have a B&K "Dynaquick 600" (something like that). I don't use it much because it misses too many bad tubes. I keep it around because it sort of tests some really new types.
Buying one of those today is a waste of money unless it's really CHEAP and you intend to buy a real checker also.
-Chris
Problem is, some tubes normally show shorts between one set of elements. You need to know which ones. That and most testers use a heater voltage drop to check "life". My 9-66 does as well.
Seems to me that the fastest test is to try another tube, or measure the circuit voltages. If you were to leave your TV-7A/U out on the bench, it would be as easy to test using that. Both types require a bunch of settings and there is a "good/bad" or "English" scale on yours too.
I also have a B&K "Dynaquick 600" (something like that). I don't use it much because it misses too many bad tubes. I keep it around because it sort of tests some really new types.
Buying one of those today is a waste of money unless it's really CHEAP and you intend to buy a real checker also.
-Chris
GordonW said:
anatech said:
Thanks for your input Chris and Gordon. I was telling my other friend Chris that the faces of the scopes look like the instrument panel on a 747! Guess that'll clear up once I know the basics of it. I've found a few scopes on Ebay. Item number 330201921105 caught my eye. If you guys get a chance check it out and see what you think. I'm thinking for old am radios the 10mhz would work fine but then down the line.......?
Thanks again for all the help!
Steve
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