Re: Tube testing

Tubes Asylum

Questions about tubes and gear that glows. FAQ

In Reply to: Tube testing posted by Chubby on August 21, 2001 at 07:24:41:

Since most testers are at least 25 years old, maintainance and calibration are important. There are still a few folks that do wonderful work. Remember that your +/- $250 purchase of a TV7 is only the first step. Plan on another $150+ to get it professionally calibrated if you can't do the work yourself.
A tube tester will provide some information, but the only "true" test of a tube is a working circuit. Sure, screening an expensive tube in a tester is worthwhile, but you just get one point on a curve. Still an AVO or Hickock will weed out a large percentage of bad tubes.
Several examples. A mutual conductance tester may pass a sweep tube, but when pushed in a linear amp it may fail totally. A 5U4 will often test fine - as most testers put at most 150v on the plate - but arc over in a circuit. Tubes with dual diodes and a triode will often test weak on one of the diodes, yet function fine in a circuit (where typically both diodes are wired in parallel anyhow). A 45 may test weak, yet sound fine in a radio or less critical application.
I have a small accumulation of TV7's, and Hickock 539b/c's among others. A reasonable "sleeper" is the Eico 666/667, often $45-50 at hamfests. While not a true mutual condutance tester, it works well and tends to agree closely with the others. The only caveat is that the 667 lacks sockets for earlier types and the appropriate adapter is fairly uncommon.
Alan Douglas's book on tube testers is tremendous, WELL worth the $26 if you have an interest in the subject. Also Steve Bench's website has plans for a DIY tester!

Gary's Tube Page (Open in New Window)

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Follow Ups Full Thread

Topic - Tube testing - Chubby 07:24:41 08/21/01 (12)

Some points to consider... - mb-de 02:05:30 08/22/01 (1)

Re: Some points to consider... - chubby 05:17:12 08/22/01 (0)

Re: Tube testing - Gary Kaufman 08/21/0115:14:01 08/21/01 (0)

If your a newbie.... - mrfixit 12:02:39 08/21/01 (0)

Are your tester calibrated? - Ehien 09:59:39 08/21/01 (0)

Re: Tube testing - kentaja@yahoo.com 09:53:44 08/21/01 (1)

Good sound advice. nt - John PA 10:42:51 08/21/01 (0)

Re: Tube testing - 7N7 08:45:19 08/21/01 (0)

Ebay is scary - Snert 08:28:42 08/21/01 (0)

Re: Tube testing - PÃ¤r 07:27:34 08/21/01 (2)

So that's how they get. . - John PA 08:09:32 08/21/01 (1)

Re: So that's how they get. . - PÃ¤r 23:42:02 08/21/01 (0)

Follow Ups

Re: Tube testing - Gary Kaufman 08/21/0115:14:01 08/21/01 (0)

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