Description
You are bidding on a VERY NICE example of a WW2 US Army / Air Force General Radio 650A Impedance Bridge Oscillator!
The GR 650-A was a general purpose CRL (capacitance, resistance and inductance) bridge. It was designed by R.F. Field, who joined General Radio Corp. in 1929, and introduced it in the April-May 1933 issue of The General Radio Experimenter. It covers capacitance from 1 pF to 100 uF, resistance from 1 milliohm to 1 megohm and inductance from 1 microhenry to 100 henries. Accuracy is generally better than 2%, save for dissipation factor and inductance measurements. The 650-A does not contain its own bridge transformer, so care must be used if you supply your own signal source. The battery operated microphone hummer and battery-based DC supplies are, of course, fully floating. The 650-P1 contains its own low capacitance signal isolation transformer.
Made of aluminum, bakelite, wood, and steel, this testing unit is in EXCELLENT used condition. Though there are some scratches, marks, and wear, it appears to be 100% complete! Retains MUCH of the original finish, however, there is some surface corrosion/discoloration from being stored in a barn. Could use a bit of a clean-up. It is 100% mechanically functional, however I have not tested it electrically. Would make a PERFECT addition to any collection or display!
