Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: legg Newsgroups: sci.electronics.repair,sci.electronics,design Subject: Re: PSU Ripple Date: Sun, 10 Mar 2024 14:05:52 -0400 Organization: A noiseless patient Spider Lines: 35 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Info: dont-email.me; posting-host="6b3a8df777a17fe1b6174ba9839775e0"; logging-data="3258150"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/DtbbyMF1dRyLJ9YfKzWaI" Cancel-Lock: sha1:meEWtkRzSmhN+lsuR3NQXv05wUM= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 2249 On Sun, 10 Mar 2024 13:35:18 +0000, Cursitor Doom wrote: >Returning to this Marconi signal generator which has a lot of ripple >on the (linear) PSU output, I managed to get probes through a barely >accessible crevice and get a couple of screen shots of the rectifier >outputs I'm seeing on the scope. > So there's mains incoming which goes into a toroidal transformer and >thence to the rectifiers. There are two secondary windings on the >transformer and they each get their own bridge rectifier. This is the >waveform that's being applied to the storage caps of the PSU (which >I've disonnected for testing purposes). >The outputs of neither rectifier look at all correct to me. What does >the Panel make of them? > > >https://disk.yandex.com/i/CP8qRMy-QA-fCg >https://disk.yandex.com/i/ubNazf1pFhuNtg > >(probes are on 10x and I did compensate them first) Glad to see you tackling something fairly basic, sport. Care to mark up your images to include a 0V baseline? With the bulk caps removed, I trust you are not applying full mains voltage - just enough to get a diagnostic waveform, with a load resistor in place.There will be other cicuitry going bonkers, if not. Most technicians in this situation will just check/replace the bridges. If that doesn't do the job, only then is it time to speculate. RL