This useful homebrew bench power supply was first built in 1983.
In 2013 RF protection was added to enable it to be used in high RF fields with no ill effect.
The power supply is 30 years old now and still in daily use!
In 2001 after 18 years of use, it stopped working. It was then lovingly rebuilt using the original transformers, case and LED displays. An improvement was made to make the output voltage adjustable down to 0.00V using negative bias to the regulator. (The previous LM317 regulator design could not be set lower than 1.20V.)
The supply can operate in constant-voltage or constant-current mode.
Click on a thumbnail below to see a larger picture
The 7-segment LED displays are mounted in 90° IC sockets.
The voltage and current are measured with two ICL7107 3½-digit meters. The displays resolve to 10mV and 1mA. Click here for the ICL71707 datasheet (PDF 534kB).
The voltage control is a 10-turn wirewound pot for precision voltage setting.
The LED between the voltage and current displays illuminates in constant current mode.