From: jl@glen--canyon.com   
      
   On Thu, 15 Jan 2026 17:51:59 +0000, liz@poppyrecords.invalid.invalid   
   (Liz Tuddenham) wrote:   
      
   >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.   
      
   Yikes. That would be a huge diversion from getting a product done.   
      
   I found one paper that shows that thinfilms are tougher than   
   thickfilms, but thinfilm MELFs are even better. That makes sense.   
      
   I'm not a fan of MELFs - they roll off ones bench onto the floor - but   
   a boy has to do what he has to do.   
      
   https://www.vishay.com/docs/28870/pulseloadsmdlimit.pdf   
      
      
   John Larkin   
   Highland Tech Glen Canyon Design Center   
   Lunatic Fringe Electronics   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)