Path: ...!weretis.net!feeder8.news.weretis.net!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: Re: PSU Ripple Update Date: Sun, 17 Mar 2024 19:43:26 +0000 Organization: A noiseless patient Spider Lines: 34 Message-ID: <8thevihekldea82a80e1p7o5biujefnj73@4ax.com> References: <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="3888390"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19f31/cKXoTV9lD6RCjqkGgQnNBMJ04sgM=" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:XTxyubJhdFTpnMuTpSkqvr661JM= Bytes: 2518 On Sun, 17 Mar 2024 11:33:12 -0700, John Larkin wrote: >On Sun, 17 Mar 2024 17:48:07 +0000, 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? >> >>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. Yes, it's a fault alright. The ripple is superimposed on the output of the RF generator; it's impossible to ignore.