Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Cursitor Doom Newsgroups: sci.electronics.design Subject: Re: PSU Ripple Date: Sun, 10 Mar 2024 21:44:36 +0000 Organization: A noiseless patient Spider Lines: 37 Message-ID: <0aasuipp82ak2jl7j3av7bbkoafj563aql@4ax.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Info: dont-email.me; posting-host="2982adc9a211c867e1a7bf94a4046e9a"; logging-data="3348293"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+TsNDDzy7Kt6vrqP0bCDgZ3jlycqo6/Aw=" User-Agent: ForteAgent/8.00.32.1272 Cancel-Lock: sha1:Pla8uRijR7fH0IU1PcPmuXammx4= Bytes: 2457 On Sun, 10 Mar 2024 21:36:21 -0000 (UTC), Phil Hobbs wrote: >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) >> > >If the bridges were working properly, there should be very little 50-Hz in >the ripple. > >Looks like a bad diode in one of the bridges causing a lot of fault current >in one half of the secondary, and so messing up the other supply too. > >Cheers > >Phil Hobbs Thanks, Phil. Getting those rectifiers out will take some major surgery and I just wanted verification that by devoting some considerable time and effort into getting at them wouldn't be a complete waste of time. I shall proceed with the extrication!