XPost: sci.electronics.design
From: cd@notformail.com
On Mon, 25 Mar 2024 10:18:07 -0400, legg wrote:
>On Sun, 24 Mar 2024 18:20:58 +0000, Cursitor Doom
>wrote:
>
>>On Mon, 18 Mar 2024 07:19:08 -0400, legg wrote:
>>
>>>On Sun, 17 Mar 2024 17:48:07 +0000, Cursitor Doom
>>>wrote:
>
>>>
>>>Did you replace the rectifiers, until something (anything) changed?
>>>
>>>The ripple has changed since your last photo, as have your test
>>>conditions. You still don't indicate a 0V reference, so we can't
>>>tell what the % ripple IS.
>>>
>>>This waveform shows equal phase peaks at the expected frequency.
>>>
>>>What is your problem?
>>>
>>>RL
>>>frequency.
>>
>>I fell into the same old trap as last time and the time before that
>>and the time before that....
>>It was nothing to do with the PSU. I eventually tracked it down to a
>>coax's shield in the RF section which had come adrift. When
>>re-grounded, the ripple on the output completely vanished. Must have
>>been somehow picking it up from the mains transformer despite all the
>>screening and compartmentalisation in this device.
>>All that time I wasted on the PSU - just because ripple *has* to be a
>>PSU problem, doesn't it. Until it isn't, that is.
>
>Good to hear you've tracked down the problem.
>
>Actually measuring the output ripple of a functioning linear
>can be an issue, as you're often expected to measure microvolts
>on a DC level repeatedly - requiring carefull decoupling, probe
>technique and sometimes external amplification, if the spec is
>typically silly.
>
>Suddenly you will become aware of all of the unshielded sources
>of low frequency interference in your work area.
>
>RL
Indeed. Anyway, if they hadn't made it such a bitch of an area to
inspect, I'd have spotted the issue at the outset.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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