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Date: Sun, 17 Mar 2024 16:05:46 -0400
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Subject: Re: PSU Ripple Update
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On 3/17/2024 1:48 PM, Cursitor Doom wrote:
> Gentlemen (and others)
> 
> I only get a few spare minutes a week to look into this, hence this
> update. Hopefully my latest finding might ring a bell for some of you
> and assist in pinpointing the fault with this (linear) PSU.
> So, I've carried out a few more tests and discovered that there is a
> total absence of ripple on the storage caps when all the downstream
> circuitry has been disconnected. So it's totally fine with no load.
> However, as I re-connect all those downstream circuits, the ripple
> commences and the more connectors I re-attach, the worse it gets. This
> is a screen shot showing over a volt of ripple at only about 66% of
> the full supply voltage applied:
> 
> https://disk.yandex.com/i/vgxfpXgNp-F4Yg
> 
> Now I did check to see if there was anything downstream which had
> shorted or gone low-resistance which could possibly account for this,
> but found nothing amiss. So the question is:
> What could cause ripple to arise when even very light loads are
> applied to the output of a pretty substantial linear PSU?

You sure you got your probe division/scope division configured congruently?