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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.repair,sci.electronics,design
Subject: Re: PSU Ripple
Date: Sun, 10 Mar 2024 14:05:52 -0400
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On Sun, 10 Mar 2024 13:35:18 +0000, 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)

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