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From: Cursitor Doom <cd@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: PSU Ripple
Date: Sun, 10 Mar 2024 21:44:36 +0000
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On Sun, 10 Mar 2024 21:36:21 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Cursitor Doom <cd@notformail.com> 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!