From: phil_a@tpg.com.au   
      
   "Phil Allison"   
   >   
   > But I do have an all valve Wien Bridge oscillator using a dual gang   
   > condenser, taken from a 1940s radio.   
   >   
   > Owned it since I was 15 years old.   
   >   
   > Tube line up: 2 x  Mullard 6AM6, 1 x  AWV 6BQ5 &  1 x Miniwatt 6V4   
   > rectifier.   
   >   
   > Three ranges:  19 to 218 Hz,  185 to 2158Hz  &  1889 to 21,899Hz.   
   >   
   > Two 18 megohm resistors used in the low frequency range.   
   >   
   > The 6AM6s are wired as triodes.   
   >   
   > Stabilisation is by an R53 NTC vacuum bead thermistor.   
   >   
   > The condenser is electrically isolated from the chassis and lives in a   
   > steel box of its own for shielding.   
   >   
   > The shaft is driven by a backlash free, 60:1 worm reduction drive and a   
   > 200 point scale.   
   >   
   > Verrry silky.   
      
   ** Ambiguity fix.   
      
   The 200 point scale is engraved on a 4.4 inch dia steel disk that rotates   
   with the worm drive, making 6000 setting points per range.   
      
   30 turns x 200 = 6000.   
      
      
   ...  Phil   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)