On 9.7.17 23:44, Cursitor Doom wrote:
On Sun, 09 Jul 2017 12:34:51 -0700, mike wrote:

You might get this when you have two caps separated by an inductor.
First cap usually gets more peak charge current than the second one and
develops high ESR first. Even if both caps are good, the inductor (or
resistor) in between can cause this effect.

Someone on SER said a non-linear load could explain the shape of that
trace and my initial reaction was that sounded quite plausible. However,
on reflection I think if that *were* the case, then the knee would span
600-700mV (when the semis start conducting) and that isn't what we see
here.
The obvious thing to do next is whip off the output plugs from the PSU
one by one and see if that clears the problem and if so, which sub-
circuit is responsible for the overload as it may be nothing to do with
the PSU at all.


The peak is definitely from the charge pulse from the rectifier. A
capacitor-input PSU charges only 5 to 10 % of the half-cycle time,
depending on the resistances and inductances in the charge path.

--

-TV