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