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Strength of 45 Tubes....How weak is too weak?........

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Posted on December 15, 2014 at 08:27:22
Cut-Throat
Audiophile

Posts: 18286
Location: Minneapolis - St.Paul Area
Joined: September 2, 2000
Contributor
  Since: May 16, 2021
 I have some Welborne Starchief 45 amps that I have been running for close to 10 years now. I have had some RCA Globe UX-245 Tubes in them for about 5 years. I decided to test them and they tested about 700-800 mhos on my Hickok 539A Tester. The Spec that is listed says they should be 1170 for good.

I have heard that a SET amp does not push these tubes to hard, so they may work well even at lower test numbers.

My question is when do you replace them? I've got plenty in stock in my Tube Stash and the stronger ones don't sound any better than the weak ones. Is it fine to just 'Let them Fail' or should I replace them sooner. IOW - How weak is Too Weak?



 

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RE: Strength of 45 Tubes....How weak is too weak?........, posted on December 15, 2014 at 11:03:03
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 Try a better testing set of tubes and listen for differences. Weak tubes will sound bad!

 

RE: Strength of 45 Tubes....How weak is too weak?........, posted on December 15, 2014 at 14:42:40
amnesiac
Audiophile

Posts: 717
Joined: August 21, 2002
 Its time to pull them and sell them on ebay as test like new!

 

condition of your 539A?, posted on December 18, 2014 at 08:07:04
Lew
Audiophile

Posts: 10912
Location: Bethesda, Maryland
Joined: December 11, 2000
 For example, do you have some known NOS type 45s that do test higher on the same tester? I know my 533A cannot elicit "normal" transconductance from some very current-demanding small signal triodes I own, in this case, 6900s. NOS 6900s test way low on my machine. Same is true to a lesser extent for medium mu/medium Gm tubes, like 6SN7. I just use NOS samples as "controls" when trying to evaluate used tubes.

 

RE: condition of your 539A?, posted on December 18, 2014 at 09:09:27
Cut-Throat
Audiophile

Posts: 18286
Location: Minneapolis - St.Paul Area
Joined: September 2, 2000
Contributor
  Since: May 16, 2021
 The 539A has recently been Calibrated. I have plenty of Old Stock 45 Tubes that test very Strong. As New. My new Production 45s are similar testing as the Old Stock ones.



 

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