From: pcdhSpamMeSenseless@electrooptical.net   
      
   On 2023-07-23 19:04, Dave McGuire wrote:   
   >   
   >    Hi folks, I'm looking to identify what I think is a transistor, in a   
   > TO-72 package (TO-18 with four leads), in an old Victoreen radiation   
   > survey meter.  The number is "ITS 30487".  It's also marked "7736" which   
   > I assume is a date code.   
   >   
   >    Can anyone tell me what this is?   
   >   
   >                 Thanks,   
   >                 -Dave   
   >   
      
   Probably an internal part number. BITD transistors were commonly marked   
   with customer part numbers.  (Around 1982, I was working in a group of   
   RF engineers, and a lot of the parts available for us to use had cryptic   
   part numbers like that.   
      
   I assume that one of the leads is connected to the case (the usual   
   situation).   
      
   If it's the front end of a proportional counter, it might be a FET such   
   as a 2N4117A JFET or a 3N163 MOSFET.  For a Geiger counter, it would   
   probably be something a bit more robust such as a 2N2222.   
      
   If none of the leads is connected to the case, it could be something   
   less common, such as a dual-gate FET.  I used to use a lot of 3N201s in   
   that package.   
      
   Cheers   
      
   Phil Hobbs   
      
   --   
   Dr Philip C D Hobbs   
   Principal Consultant   
   ElectroOptical Innovations LLC / Hobbs ElectroOptics   
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