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IBM Computer Pluggable Capacitor Unit



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This is called an IBM Pluggable Unit using a Cornell Dubiler Capacitor tube and supporting electronics for the 650 family of computing machines.  It dates to 1953 and identifiable by the extended leg on one side.  Prior Pluggable Units did NOT have this extended leg and it was added to prevent pin damage if incorrectly plugged in.  Included is an original IBM advertisement describing their new revolutionary computer development called the Pluggable Unit and states “Piercing The Unknown”.  This was a new and revolutionary idea of the era.   In 1948 IBM announced the 604 Calculating Punch Machine that used an internal circuit called a “Pluggable Unit” for NOT, AND comparison logic and mathematical calculations that could quickly be removed if it failed and new replacement inserted.  Prior machines often times failed and would take many hours, days and even weeks to repair.  That is because supporting circuitry for the electronics was internal to machine and NOT easily repaired.  The IBM 604 and later machines could have as many as 1,400+ tubes or Units and a few of these rare Pluggable Capacitors and it was important to diagnose point of failure and easily swap out failed Pluggable Unit with new Unit.  The Size of this unit is 5” in length.  These 50+ years old Pluggable Units are rarely found as most are now in museums.  This is a very rare treasure of computing history and belongs with a serious collector or computer museum.

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