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Post by wayben on Jan 9, 2011 11:39:08 GMT -7
I'm thinking of picking up a tube tester, but don't know much about them. If anyone can recommend certain brands or what to look for that would be very helpful. It would just be for my own use, to check condition of my own and friends tubes. I don't need anything real fancy, but want something functional. Any info or if you can point me to a good info source is much appreciated. Thanks.
Wayne
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Post by BritInvasion on Jan 10, 2011 8:34:09 GMT -7
I'd like to know this too! Hope somebody knows one they could recommend.
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Post by Lefty on Jan 10, 2011 8:55:31 GMT -7
Unless you plan on buying large quantities of used or NOS tubes you don't really need one.
It has been my experience the only testers out there are the old Drug Store type and they only check to see if the tube works or not (continuity), not for sonic qualities. The best tube tester is the amp you plan to put it in.
I have in the past kept a small tube amp around for testing the micro-phonics of pre amp tubes. Plug em in, turn it up, and give it a small tap. And for power tubes, your guess is good as mine, if it works, great, if not, trash it.
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Post by teleric on Jan 10, 2011 9:13:12 GMT -7
For testing guitar tubes, you want a "Mutual Conductance" (or transconductance) tester, not an emission tester. Emissions testers read the flow of electrons from the cathode to a diode "short" on the tester - they test for the emission of electrons from the cathode of a tube - not the most accurate test. Mutual conductance testers on the other hand, test the flow from the cathode to the plate and is a more accurate way of determining the gain of a tube. The Hickock 539 (B or C model) is the gold standard of tube testers. Hickock 600 series are also very good. Hickocks are generally fetching over $1000 in good condition Hickock owned the patent on mutual conductance testing, so this is probably why they're revered as the gold standard of tube testers. Another issue to keep in mind is that testers are "tube creatures" as well, meaning that many of them run a rectifier tube and some sort of triode in the the internal circuit. This means that they require occasional calibration to produce meaningful results. The calibration process is quite complex and should be performed by someone who knows what they're doing. Since the '50's & '60s is when most tube testers were manufactured, any tester you buy will probably require some sort of calibration (which runs about $100). I own a B&K 747 tester. they're considerably less expensive than Hickocks and the 747 is a solid state tester, so it doesn't have the internal tubes and as much of the correcsponding drift that requires frequent calibration (it does need to be calibrated, just not as often as the type with internal tubes). I paid $150 about 5 years ago for my tester. I've had it calibrated once since I've owned it. The only downside of the B&K tester is that it reads transconductance in terms of "% good" rather than actual Gm or micromohs. However, you can get an approximate Gm reading by running a few "known" tubes through it and noting the scale of % good to known gm. The B&K also has a gas/leakage test and life test as well and will test any tube. To my knowledge, vacuum tube valley is the only current manfacturer of consumer level transconductance testers. They're might be others out there, I just haven't run across them. Here's a link that provides way more info than you will need for acquiring a tube tester. It has a handy chart at the end with the pros & cons of many units. www.tone-lizard.com/Tube_Testers.htmlHope that helps.
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Post by BritInvasion on Jan 10, 2011 13:16:07 GMT -7
Interesting info , thanks teleric . More to it than i realized , Matt your idea of pluggin' em in and making the call might be more up my alley.
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Post by doctorice on Jan 10, 2011 13:53:57 GMT -7
I have an old B&K also. It has been helpful, but is now in need of calibration.
teleric: any places you'd recommend for the calibration work?
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Post by pintail78 on Jan 10, 2011 14:29:52 GMT -7
i have cheap eico, never calibrated it but gives a good relative idea if things are good, weak or bad, works good for me and cost less than 100$.
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Post by BritInvasion on Jan 10, 2011 18:00:14 GMT -7
Where do you get the elco? Is it still made?
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Post by teleric on Jan 10, 2011 18:38:45 GMT -7
In terms of "why buy a tester", it does come in handy for:
Tube swapping in amps - if you're trying to get a little more/less dirt out of the preamp, being able to identify the higher gain tubes is a little easier (and much quicker) than swapping them out and playing through each one. You can also identify the balanced tubes for PI use (and match power tubes if you happen to have "spares").
Buying tubes on ebay - I frequently look for the "old Mullard - don't know if it works" auctions on ebay that rarely get any bidding action. You can score some great ANOS tubes for under $15, often less than that. The tester just helps me know what I'm getting from ebay autcions to a degree.
I've got a few friends who come back from garage/estate sales occasionally with boxes of old ham radio tubes & will throw me a few from the lot (usually rectifier tubes since the 5V4 is common in ham applications - I've got quite a few old 5V4s). Again, it helps me determine what I've got and I'd rather know if a rectifier tube is good before putting it in my amp so I'm not blowing the 3amp fuse.
It's also helpful in troubleshooting amp problems, so you narrow down if the issue is a bad tube or not.
Bottom line - testers are a bit of a luxury, but they're nice to have around if you're into troubleshooting your amps rather than relying on a tech. Bench times for amp techs in my neck of the woods are fairly long (6-8 weeks), so I'm constantly trying to learn what I can about my amps so that the trip to the tech is not necessary - the tester helps in that regard.
Ice:
Doutt Electronics in Sarver, PA has calibrated my B&K in the past (www.bktestequipment.com).
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Post by wayben on Jan 10, 2011 19:14:34 GMT -7
Wow, a lot more to it than I thought, but interesting. I guess I tend to agree that the real test is what it sounds like in an amp, but sometimes I just gotta know why. Maybe understand a little more about why one tube sounds so great and another not so much. Thanks for the info and link, that will get me going. Kind of liking the B&K for a little more stability.
Wayne
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ksks
Full Member
Posts: 120
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Post by ksks on Jan 11, 2011 6:09:56 GMT -7
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Post by chetz on Jan 13, 2011 23:27:52 GMT -7
;D ;D ;D
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Post by doctorice on Jan 14, 2011 10:13:55 GMT -7
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