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.
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