Old power supply ripple waveform

[dobsonr741]

Restored an old 723 based power supply. The +5V output giving an interesting looking ripple waveform under 1.5A load. Solid flat no ripple under no load.
Does anyone know what it might signify? The frequency is 60Hz.

[Mazo]

Simple PSRR+some funky rectification effects in the internal circuitry?

[bdunham7]

Can you put the scope on points E20 and E23 and look for switching noise from the rectifiers (short spikes at 120Hz) and get a general idea of what the input looks like?  And what is the value of C3, I can't read it.

My first thought is that the regulator circuit is not reacting perfectly to rectifer switching noise since there appears to be no RC snubbing of the bridge.  Too high a value for C3 might make the system slow. 

I would observe that your ripple or noise is fairly small, <2mV_RMS, so I'm not sure you have an actual defect.

[dobsonr741]

I agree, it's not a defect. I think it's impressive from an original 1983 supply, with no parts replaced, all electrolytes are original. The ripple, as attached, on C1 is 1V, when at 3A to a resistive load.

The shape of the waveform caught my eye, and the phase difference relative to the C1 ripple.  The 12V section ripple is much better, interesting enough. Perhaps the 2N3055/TIP31 on 5V is way tooo slow.