Here is a view of my version of the SCELBI O-scope Opamp Power Supply test setup. AC power is not connected in this photo, but would be connected to the transformer during the actual test.

Opamp Power Supply

I’m using a Triad VPL28-180 transformer and 1N4002 diodes. I found the diodes in my spare parts stash. The first smoothing capacitor is rated at 100uf/50 Volts. The +18 and -18 supplies have 470uF/25 volt smoothing capacitors. The latter are probably overkill, but it’s what I could find in my spare parts stash. The resistors are rated at 120 ohm, 1/4 watts. The zener diodes are the BZX79C18 that I mentioned in a previous post.

After hooking up to the analog board, the voltages are within a volt of +/- 18, with no measurable ripple. Transformer output is a little higher than with the original transformer that I tested with, but not enough to be of concern. Zener shunt current is OK, so I’ll just move this set up into the enclosure, without changing any components.