On Sun, 9 Jul 2017 15:10:46 -0000 (UTC), Cursitor Doom
wrote:

Gentlemen,

Surely, you jest.

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...posted-public/

Is the mystery load the hardware appearing in adjacent photos? EXIF
says that they were taken 4 days earlier, which suggests a connection.

These photos looks odd:
https://www.flickr.com/photos/128859641@N02/34892442244/in/photostream/
https://www.flickr.com/photos/128859641@N02/35564536392/in/photostream/
because C17 (the 2nd blue electrolytic from the right) seems to have
been soldered into the wrong PCB holes. The white silk screen circle
makes a good target for installing capacitors. If my crystal ball is
correct, this capacitor might be presenting a higher than normal
current load to the power supply, which is reacting by producing
excessive ripple that you're seeing on the scope.

Is this the capacitor you removed from the board?
https://www.flickr.com/photos/128859641@N02/35050368241/in/photostream/
If so, you ripped out the plated through hole. 4 terminal radial caps
are not common, so I guess you substituted something else. What did
you put in its place? Did you test and fix the PCB traces?

Oh, never mind. I found your rather ugly solder wick PCB fix:
https://www.flickr.com/photos/128859641@N02/35602405551/in/photostream/
You might want to double (or triple) check your soldering and PCB
through hole connections.

From this photo:
https://www.flickr.com/photos/128859641@N02/35564539582/in/photostream/
there's a tuning screw, semi-rigid coax cable, and cavity filter on
the left side. Too bad the power supply board is missing. There are
some gold connector pins in the photo. So, what is it?


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558