"David Eather" wrote in message
news
p.y24qvzulwei6gd@fx-6300...
On Mon, 10 Jul 2017 01:10:46 +1000, Cursitor Doom
wrote:
Gentlemen,
The link below shows a scope trace of the output of a linear PSU (voltage
4.7VDC) with about 300mV of 100Hz ripple riding on it. This PSU is in-
circuit under load from the boards it supplies. Normally I would assume a
filter capacitor to be at fault here, but they all check out fine so
something else is causing this ripple. Note there is a characteristic
'knee' on the high peaks and I'm thinking this must be indicative of
*something* trouble is, I don't know what. If anyone recognises this
waveshape and knows what causes it, that'd be "awesome" - as our American
friends describe everything. Check it out:
https://www.flickr.com/photos/128859...in/dateposted-
public/
a soft diode in the bridge rectifier?
--
It is showing two half cycles at 50 Hz and they are the same. Most likely
not a diode issue. Most likely a bad capacitor with high ESR. Or you got the
replacement capacitor in the wrong holes on the pc board. Can you remove the
new cap and get a photo of the top side of the board?