On Sun, 09 Jul 2017 19:37:39 -0400, tom wrote:
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It is showing two half cycles at 50 Hz and they are the same. Most
likely not a diode issue. Most likely a bad capacitor with high ESR. Or
you got the replacement capacitor in the wrong holes on the pc board.
Can you remove the new cap and get a photo of the top side of the board?

When I tested this psu out-of-circuit with a dummy load I got less than
5mV of ripple on that rail. Now I may have too lightly-loaded the output,
I can't say for sure, but that does tend to indicate to me I should check
for shorted components down the line from the psu before I do anything
else.