From: none@ntlworld.com   
      
   On 05/09/2010 15:55, Richard wrote:   
   > On 05/09/2010 12:33, Patrick Turner wrote:   
   >   
   >>   
   >   
   >>   
   >> Most people have utterly no clue about what the tube tester tests   
   >> mean.   
   >  >   
   >> Patrick Turner.   
   >   
   > Let's just say that I wanted to make a dedicated tube tester for my   
   > KT88's. Not just test the tubes, but to enjoy the experience.   
   >   
   > Okay, let's take this step by step and let's just concentrate on each   
   > step. Let's just deal with steps 1 and 2 for now.   
   >   
   > Of course, if the tube is faulty it may turn up in the early stages of   
   > testing and testing would stop early on.   
   >   
   > STEP 1: Measure heater continuity.   
   >   
   > If an open condition - stop testing.   
   >   
   >   
   > STEP 2: Electrode leakage (Cold). If failure stop test.   
   >   
   > What electrodes are tested? And what voltages? AC or DC?   
   >   
   > a) Heater to Cathode (What Voltage?)   
   >   
   > b) Cathode to G1 (What voltage?)   
   >   
   > c) Cathode to G2 (What voltage?)   
   >   
   > d) Cathode to G3 (What voltage?)   
   >   
   > e) Cathode to Anode (What voltage?)   
   >   
   > etc.   
   >   
   > I'm not actually sure which electrodes should be tested in relation to   
   > other electrodes. I believe some electrodes would be connected together   
   > in the leakage tests. Anyone know all about the leakage part of testing?   
   >   
   > Can anyone give me an idea of a suitable circuit (components) just to   
   > test KT88's for leakage? A circuit that protects a meter.   
   >   
   > After leakage is sorted, then I can go to another specific step in testing.   
      
   To try to answer my own questions:   
      
   I see that the data sheet mentions 4 maximum voltage ratings (ignoring   
   triode connection):   
      
   Va 800V  (presumably between k and a)   
   Vg2 600V (presumably between k and g2)   
   Vh-k 250V   
   -Vg1  200V (presumably betwen k and g1)   
      
   So, we have:   
      
     TEST LEAKAGE VOLTAGES   
      
   a) Heater to Cathode 250V   
      
   b) Cathode to G1 200V   
      
   c) Cathode to G2 600V   
      
   d) Cathode to Anode 800V   
      
   But I think there are some few other leakage tests connections that I've   
   missed.   
      
   Any comments?   
      
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