From: roger@hayter.org   
      
   On 3 Sep 2025 at 15:03:52 BST, "Cursitor Doom"  wrote:   
      
   > On 3 Sep 2025 13:56:25 GMT, Roger Hayter  wrote:   
   >   
   >> On 3 Sep 2025 at 14:20:34 BST, "Cursitor Doom"    
   wrote:   
   >>   
   >>> Gentlemen,   
   >>>   
   >>> I have an early AVO valve tester (twin panel type, Mk1 or Mk2) which   
   >>> I'm trying to get fully working. Anyway, I have a problem with it   
   >>> which I've never encountered before. I set the panels up to test a   
   >>> valve, set the anode and heater voltages etc, the valves are glowing   
   >>> just like they should, but when I apply the prods of a DVM across the   
   >>> heater pins to check if they're correct WRT the switch setting, that   
   >>> tiny extra load completely collapses the supply to the heaters! The   
   >>> meter reads 0V (or close enough) and the heater glow dims to nothing.   
   >>> Any idea WTF's going on here?   
   >>>   
   >>> Cheers,   
   >>>   
   >>> CD   
   >>   
   >> Suppose you didn't actually use a bench DVM with one input connected to   
   mains   
   >> earth?   
   >   
   > I'm using purely battery-powered DVMs for this project. I don't even   
   > have a bench DVM. Perhaps I'll try a scope instead and see how it   
   > reacts to that.   
      
   It is a mystery then.  Loose connection somewhere?   
      
   --   
      
   Roger Hayter   
      
   --- SoupGate-Win32 v1.05   
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