Oct 022012

I picked up this Tektronix 575 Curve tracer at an estate sale this weekend for $50. It seems to basically work, although if you look closely, you’ll see that the out and back I-V sweeps on the 2N2222 IV curve don’t lay on top of each other.

This is the Tek 575 as as found it in a barn. Seventy pounds of awesome!

Restoring this unit will be my introduction to vacuum tube electronics! Like I need a new project!


This looks almost OK, but notice how the up and down voltage sweeps aren’t the same.

Here’s the collector I-V of a transistor as the base current is stepped. The fact that the curves are almost horizontal tells you the collector current isn’t much of a function of collector voltage; it depends mostly on the base current, which is stepped up and down to generate the family of curves.

Here’s the collector I-V curve of a 2N2222 transistor as the base current is stepped. Each I-V curve for a given base current should lay on top of each other.


And finally, I shorted the collector to ground, turned off the base stepping, and set the x-axis to display base volatge (should be constant). I don’t get a vertical line.


Collector shorted to ground via a 1k load resistor. Should be a vertical line. About 2V of collector sweep.

I’ll document my progress getting this unit back into spec. The fact that it basically works makes me hope that it’ll be a relatively straightforward job.

 Posted by at 5:58 PM