We find a signal tracer to be indispensable when repairing old electronic gear. One
of the most venerable is the Eico 147A. So we took a 147A and improved it.
We replaced the "magic eye" with an audio voltmeter, calibrated in dB, to allow us
to measure signal to noise ratio. We also added a multitap audio transformer to
allow use with 500, 8 and 3.2 ohm sources and separate pads to adjust the speaker
volume and meter response independently.
Click on the images to the left to get a close up of our modified signal generator and
its modified schematic.
Click on any picture to enlarge it