Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Cursitor Doom Newsgroups: sci.electronics.repair,sci.electronics.design Subject: PSU Ripple Update Date: Sun, 17 Mar 2024 17:48:07 +0000 Organization: A noiseless patient Spider Lines: 23 Message-ID: <3haevi1jbhf4poc4s32t99391bq4tqfc42@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Info: dont-email.me; posting-host="6b68b13d0f8cd75cb4b90b640cffe83e"; logging-data="3838905"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/CRPx+7HwvCfjmRI9tfQ0gqtBKwjB7TtI=" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:O0DV/z3195ZE/ZW/aBHRG/GX7MU= Bytes: 1969 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.