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Path: Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail NNTP-Posting-Date: Sun, 17 Mar 2024 18:34:44 +0000 From: John Larkin <jl@997PotHill.com> Newsgroups: sci.electronics.repair,sci.electronics.design Subject: Re: PSU Ripple Update Date: Sun, 17 Mar 2024 11:33:12 -0700 Organization: Highland Tech Reply-To: xx@yy.com Message-ID: <mmdevil3si3to2l68lhrk9geoibkrm721r@4ax.com> References: <3haevi1jbhf4poc4s32t99391bq4tqfc42@4ax.com> X-Newsreader: Forte Agent 3.1/32.783 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 29 X-Trace: sv3-oIjv7RKZrjIrJ3odslx0XmpMMuwkHNOeJL+cuNrm70duFlgQU7T0MiWocuBrLTj5ZYEQlOlWkJo2vOy!qLangPotydUAL4BYw1z/6c0gbXiN/BiI5+Yg7JHIGy3kRhW2yPjnfKw855ED2fOEn85CI2rb19nm!28JFSw== X-Complaints-To: www.supernews.com/docs/abuse.html X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 Bytes: 2410 On Sun, 17 Mar 2024 17:48:07 +0000, Cursitor Doom <cd@notformail.com> 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? > >BTW, the bridge rectifiers were fine and have been exonerated from any >culpability in this fault. Is there actually a fault? Transformer-rectifier supplies have ripple.