That got me wondering how much the life test drops the filament voltage. I put a 6JB6A in my tester and measured the filament voltage. The tester's "normal" 6.3V was really 6.2V. The life test dropped it to 5.6V. On a 12AX7 it dropped from 12.7V to 11.6V. So it only drops the voltage about 9%.
73, Bob WW3QB --- On Sun, 1/31/10, Garey Barrell <[email protected]> wrote: > From: Garey Barrell <[email protected]> > Subject: Re: [Drakelist] What circa tube tester? > To: [email protected] > Date: Sunday, January 31, 2010, 11:41 AM > Bob - > > That's a very good site reference. Lots of good > information there. > > The "Life Test" typically just reduces the filament voltage > on the tube. This indicates whether the cathode is > straining to deliver enough electrons, (wearing out,) or has > "life" left! If the meter indications stays steady or > only drops slightly, then the tube has considerable life > left, at least from an emission standpoint. If the > meter drops a lot, not good. > > You can perform a similar test on any tube tester, merely > switch the filament voltage DOWN one step, i.e., from 6.3 to > 5 volts. A "good" tube will drop only a few divisions, > while a "weak" one will drop 5 to 10 or more divisions. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement > CDs > <www.k4oah.com> _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
