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Path: ...!news.misty.com!weretis.net!feeder6.news.weretis.net!news.cmpublishers.com!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!feeder.usenetexpress.com!tr1.iad1.usenetexpress.com!198.186.191.154.MISMATCH!news-out.netnews.com!s1-1.netnews.com!eu1.netnews.com!not-for-mail X-Trace: DXC=A_mil<6CT_ePooF4PSM31jU5[F2hIijDo7J470dMQQ7kJ4R`5ADBYnb78WECPL4LUg1A?EK]8;W0kFNhi\jji;Nff@HSLgR[]oh7dKkgDfTEDliJPUY0^i>7f X-Complaints-To: support@frugalusenet.com Date: Sun, 17 Mar 2024 16:05:46 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: PSU Ripple Update Newsgroups: sci.electronics.repair,sci.electronics.design References: <3haevi1jbhf4poc4s32t99391bq4tqfc42@4ax.com> Content-Language: en-US From: bitrex <user@example.net> In-Reply-To: <3haevi1jbhf4poc4s32t99391bq4tqfc42@4ax.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Lines: 24 Message-ID: <65f74d1b$0$876048$882e4bbb@reader.netnews.com> NNTP-Posting-Host: 127.0.0.1 X-Trace: 1710705947 reader.netnews.com 876048 127.0.0.1:47411 Bytes: 2325 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?