3 Sep
2025
3 Sep
'25
7:38 a.m.
On 9/3/25 02:24, Rob Jarratt via cctalk wrote:
Those are not real. They are conducted interference from
the switching supply getting into the scope preamp via the
ground lead.
I have seen this MANY times, ignore it.
Jon
One other
thing…
With it powered on and measuring voltage at the outputs but not at the
plugs, wiggle the plugs a bit and see if there wierdness with them.
plugs and connectors go bad often and it doesn’t seem obvious that they do
but saves a lot of time just by checking them now.
Sent from my iPhone
Replacing those caps seems to have fixed the issue, need to do a bit more testing.
However I am unsure about some spikes on the +5V output when I try to check the ripple.
This is the scope trace:
https://rjarratt.wordpress.com/wp-content/uploads/2025/09/5v-output-ripple-…
Does that look reasonable or should I try to work out where these spikes are coming from?
I replaced C21 and C35. On Aug 31, 2025, at 13:34, Wayne S
<wayne.sudol(a)hotmail.com> wrote:
Ps if you didn’t get continuity for a moment in one direction then the cap is
open. If you get continuity in both directions then it’s shorted. Hope this
helps.
Sent from my iPhone
> On Aug 31, 2025, at 13:28, Wayne S <wayne.sudol(a)hotmail.com> wrote:
>
> Rob, replace c21 because of the bulge. If you want to check an electrolytic
cap with a ohmmeter ,(kinda hard with a digital one), connect the meter
across the ends. You should get either infinite resistance or a momentary
reading of zero going back down to infinite resistance as the cap charges.
Then reverse the leads and it should be infinite from the start.
> On an old analog meter with a dial, you can
quickly tell by see the needle
deflect full scale in one direction then settle back
down to infinite. I keep an
old meter around just for this purpose. 