General Radio 1650 Wheatstone Bridge

This piece is one of several I picked up at an estate sale in June.  It’s late 60’s / early 70’s vintage, making it one of the newer pieces in my collection (and by far the newest thing I’d picked up that day).

This killed two birds with one stone:  I’ve wanted an Impedance Bridge for quite a while, and oddly enough, I didn’t own any General Radio gear until now.

This is actually an after picture


It was in pretty good condition with the exception of some flaking paint, which was due to…DSC_0134 D-cell batteries leaking their corrosive innards all over.  Boo..

The plastic sleeve & batteries were fused together.  I pulled the whole assembly and screwed it back onto the chassis facing out, in order to try to get some leverage.  DSC_0137

The tube snapped as I was trying to separate it, but fortunately the contact was salvageable.DSC_0138

Here’s the metal disc that’s supposed to keep batteries from leaking all over the inside of your instrument.  Good going there, metal disc.  You had ONE job. DSC_0139

These batteries are so old, they were made in America.  Right up the road in Tarrytown, actually. DSC_0141

Paper towel tube to the rescue.DSC_0144


Wrapped carefully in extra-wide gaffers tape for structural integrity.  Because gaff.


Reading 980 ohms on a 1k resistor.

I tested a cap or two as well which seemed to work and indicate that the internal oscillator is functioning.  It’s an interesting, if not somewhat fickle instrument.  The sensitivity control is overly sensitive, which I suppose bears some investigation.  It’s not nearly as foolproof as a modern LCR meter, you need to have some idea of the value you’re expecting, or it’s possible to get a false reading.

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