From: liz@poppyrecords.invalid.invalid   
      
   john larkin  wrote:   
      
   > On Thu, 15 Jan 2026 15:18:31 +0000, liz@poppyrecords.invalid.invalid   
   > (Liz Tuddenham) wrote:   
   >   
   > >john larkin  wrote:   
   > >   
   > >> I need something like 1.5K resistance across a 750 volt pulse. Pulse   
   > >> widths will be below 1 us.   
   > >>   
   > >> Three 1206's in series, 499r each, would work. Peak power dissipation   
   > >> per resistor will be 125 watts at 250 volts. I think that's OK but I   
   > >> want to test it.   
   > >>   
   > >> Here's the tester. The DUT (device under torture) will go across the   
   > >> gap on the left.   
   > >f   
   > >> I have both regular thickfilm resistors and some thinfilms to test. I   
   > >> theorize that the thinfilms will hold up better.   
   > >   
   > >Would a non-inductively-wound wirewound resistor work well enough?  You   
   > >would have plenty of mass to average-out the pulse energy.   
   >   
   > WWs are great for pulse overload, not so great for PCB density. The   
   > best would be to use three (or two, or one) surface-mount 1206   
   > thickfilm that we have in stock.   
   >   
   > I could stand a micohenry or so parasitic inductance. The 1.5K will in   
   > fact be in series with a small inductor.   
      
   There's your answer; make the resistor and the inductor one and the same   
   component.  For a small investment in suitable machinery this gives you   
   total security of supply, quality control and an edge over any   
   competitor who can't make things but just buys them in (or tries to copy   
   your design without realising what that component really does).   
      
   Vertical integration was the cornerstone of nearly all the successful   
   electronics firms.  (Philips even owned the sand quarries to supply the   
   sand to make the glass to make the valves and light bulbs.)   
      
   Experiment with winding a number of turns of resistance wire on a former   
   in one direction, then winding some more in the opposite direction.  The   
   ratio between the two sets of turns can be adjusted to give the required   
   inductance and the total number of turns gives the resistance.  The   
   former could be a small piece of heatproof material shaped like a dog's   
   bone to retain the wire, with a notch to catch the wire and prevent it   
   from unwinding at the reversal point.   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
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