From: info@turneraudio.com.au   
      
   You have chatted about tube curve tracers.......   
      
   after having a close look at the web site, it's a somewhat simple curve    
   tracer design, though not the way I would've designed it [example,    
   flyback HV stepup with linear regulator on the output for the plate    
   supply].  but it does look pretty straightforward and simple for someone    
   who just wants a curve tester and doesn't mind doing patch cables to    
   make it work.    
      
      
   I've been kicking around the idea of making one of these that had ZERO    
   patch cables, and could efficiently deliver up to 0.5A for the plate (at    
   certain voltages), and at the same time, enough current for the heater    
   power.  Some edge conditions for KT-series power tubes can conduct some    
   serious current (up to 1/2 an amp), and the heaters can suck up 12W or    
   so.  If the power tube can't deliver it's max current at the correct    
   plate voltage, it's essentially "going bad".    
      
   anyway, that's something that an emissions-only tester wouldn't be able    
   to test for.    
      
   but yeah, this particular curve tester goes up to 200ma which probably    
   covers most tubes.    
      
   I think the FIRST thing anyone should do to plot the Ea vs Ia average   
   characteristics of a tube is to have a real good look at the schematics used   
   in 1955, well before solid state and digital.   
   It is most remarkable that in 1955, curves were produced which gave us a   
   fairly good guide to use for load line analysis.    
      
   Why do we not build on the skills of those who preceded us?    
        
   I see that gadget at that link to the site for a curve tracer to be something   
   absolutely could not be repaired and serviced if one of the 2 billion devices   
   went phut due to high volts from tube tests.   
   I see a toy, not a tool.   
      
   To test output tubes for class A you need to have Ea max up to 1,000V. If you   
   have an SE 6550 with Ea = 500V, Ia = 50mA, then the anode swing is +/- 450Vpk   
   with a load of say 9k0. The problem with much tube data curves for Ea vs Ia is   
   that very poor    
   undefined data is available for the operation with LOW Ia typically used.   
   My solution to not having a tube tester or a curve tracer or having reliable   
   old data curves, or curves for newer Russian tubes is to set up a tube in a   
   dummy class A SE amp and measure THD and Ra then calculate gm g1 and and gm g2   
   and µ g2 and µg2 to    
   obtain the average properties at the idle condition - and its these properties   
   we employ for listening to 90% of music.   
   I have done a couple of new web pages to explain all this more better, but   
   having some trouble with page uploads and getting rid of an unwanted tracking   
   program that self-installed.   
   Patrick Turner.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)