HP Clock

Monday, March 7, 2011

Motorola Mystery

While trying to restore an older analog bench supply I discovered that the series pass transistor in all of the regulating circuits used a Motorola 1700G transistor.  The mystery is I can find no record of this device either on the Internet, or in the large collection of Motorola data books that I have.  The part is clearly marked with the famous Motorola logo and the number 1700G.  I’ve even gone so far as to dig through boxes of used books at OpAmp Labs Book Store. (http://opamp.com) By the way one of the best technical book stores in Los Angeles.

I was able to get a sense of what the device was from looking at the schematic and putting it on my Tek 575 curve tracer.  ( fixed up discard from a friend who found it at a ham-fest in Santa Barbara.)  Here is plot from the curve tracer that I labeled using Photoshop.

One of the handiest pieces of hardware that I have, other than the curve tracer, is an old scope camera that I modified by removing all of the Polaroid dependent parts from and replacing it with a shelf and baffle that accommodates a small digital camera. 

Here is a picture of the camera in use on a Tek 556 dual beam scope.

The good news is that all the series pass transistors appear to be good.  I am, however, still surprised that I can find no record of this device.  If anyone knows anything about this mystery device, let me know.