Unstable power supply output or normal?

[Elvee]

With just adding a load at the rectifier output to draw about 400mA I am getting the waveforms pictured at the OP.

Exactly that waveform? That is highly suspicious, you should see the regular 120Hz sawtooth, not this distorted 60Hz.
Can you post a pic of your set-up?

 

[Mooly]

Did you try what I suggested in post #6 ?

Any result other than a perfect thin trace points to a wiring/test measurement artifact.

 

[gootee]

I hope that more information is forthcoming, very soon.

A photo of the as-tested circuit is required.

I am wondering if the AC Mains input pair has any enclosed loop area, i.e. if it's not tightly twisted everywhere, or, if traces, if they are not extremely close together, everywhere. Same goes for secondary conductors going to rectifier bridge, and rectifier bridge to caps, and also for DC power/ground conductor pairs.

Leaving gaps between the conductors in any conductor pair that eventuially forms a loop makes what is called, in technical terms, an ANTENNA. And some seem to mostly transmit while others mostly receive. So minimize the geometric area enclosed by ALL (i.e. each) of them.

 

[Fusion916]

Sorry for the lack of update.

I have determined that it is partly a layout issue of the reference generator (TO92 bandgap reference), poor grounding, and where the scope ground was connected. I basically have to redo the layout grounding significantly.

 

[gootee]

It would be nice if we could ALL learn from this.