** The OP is clutching at straws, big fat & expensive ones at that.
He ought to very carefully check the AC supply connection from his PSU to ground - any resistance there due to tarnished pins would send EMI way up.
BTW:
a portable AM-SW radio can be used to "sniff" for the source of the EMI.
.... Phil
Phil: thanks for your comments. Yes, I am grasping at straws - I fully realize that, and as I somewhat expected, replacing the input caps did nothing to alleviate the noise.
I have checked the AC connection to ground and that is all OK.
And I have also attempted some time ago to use your trick of a small SW receiver to attempt to find the noise but cannot pin down any one component as the culprit as the noise seems to emanate from all over the output section.
I am loath to start replacing any more caps until I really determine where it is coming from...
If the output inductor of the filter fails, the unit may continue to run with excessive ripple current in the output filter and excessive switching noise, due to increased peak currents.
The filter caps will eventually fail too, bulging or otherwise, due to increasing ESR.
You would see abnormal output ripple voltage, even with good caps, if the output choke has failed.
I've seen this twice in KW rated single-output supplies, but below 12V output in both cases. Due to age, it meant rewinding the choke, rather than replacing it (and replacing previously overstressed caps...).
Output ripple was evident (>10x normal) even though there was a two stage filter.
RL
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