From: liz@poppyrecords.invalid.invalid   
      
   john larkin  wrote:   
      
      
   > It was conventional wisdom that solder can't be relied on to   
   > mechanically support components, until Tektronix just did it. Not only   
   > the ceramic strips, but they did mid-air splices. Seemed to work.   
      
   Philips were doing mid-air splices from the 1930s onwards; they had a   
   system known jokingly as a "Mitcham tagstrip"* where the component wires   
   were shoved into a 'spring' (which looked as though it was made by   
   winding tinned copper wire around a 3mm drill, then they flooding it   
   with solder.  (I have used it many times when I needed to join a lot of   
   wires together and didn't have a convenient solder tag).   
      
      
     *  The UK Philips plant was at Mitcham   
      
   >We solder relays and big transformers to boards,   
      
   Be very careful, large soldered mounting points can cool at the centre   
   due to the component extracting the heat - and at the edge due to the   
   cooler surroundings.  This leaves a circle of solder which cools slower   
   and under contraction to give a ring of dry joint.  Eventually the board   
   develops mysterious open-circuits because the centre of the tag is no   
   longer connected to the track.   
      
   I know it can happen because I have fault-found it on several occasions.   
      
      
   --   
   ~ Liz Tuddenham ~   
   (Remove the ".invalid"s and add ".co.uk" to reply)   
   www.poppyrecords.co.uk   
      
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