Re: PSU Ripple

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