Before throwing out the original T4 AC adapter I decided to open it up and take a look. With a little persuasion in a vise I carefully cracked open the glue joints around the cover. Inside I can see that C9 has a swollen top so this is likely leaking causing a high ripple. C9 is a 1000uf 16v electrolytic.
If I was energetic I would change that cap and see if it works properly again but since my receiver is ok with the replacement power supply I am gonna throw out the old one. :yes:
Just thought that I would mention this in case someone else has an issue with the adapter. It's not too hard to open and the components are easily accessible for desoldering.