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RE: Amplitrex 1000 testing MA1 6SN7, matching

71.146.25.49

Posted by Jack Williams on November 9, 2008 at 09:10:53

In Reply to: RE: Amplitrex 1000 testing MA1 6SN7, matching posted by Cousin Billy on November 8, 2008 at 13:04:50:

Hello again,

What kind of plate voltage readings are you getting ?? I use a Triplett tester and on the 12SX7, I am getting between 9-10 ma. On the GM scale they usually read about 2000 to 2100. Of course this is based how the tester is biasing the tube and at what plate voltage the tube is given. My tester may read a little low but it gives me an idea if the tube is OK or not. I use a known new tube and then I get an idea what the readings should be on used tubes. Also, don't give up on a tube if it reads a little low. I have had some tubes that read low but in service have lasted for many years in the circuit. As a matter of fact, I have the same set of 12SX7's in my M60's for over 10 years !! Those octals
seem to last a long time. I just wish the 6AS7 would do the same. The Jan RCA 12SX7 seem to be the most consistant and also sound better than the regular newer RCA 12SX7 or the GE's. Don't forget--the tester is not the last word on tube condition but it will give you an idea if the tube is dead or nearly dead or if the sections match up.

Jack
Jack

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