On 3/31/16 7:05 PM, David davidwhess@... [TekScopes] wrote:
Does the displayed ripple change with vertical sensitivity?
I want to say no. The answer will, of course, determine where it's
being injected.
It doesn't seem to change the amplitude of the ripple, but it does
displace the trace vertically (usually downward) as the sensitivity
increases (smaller volts/div), even though it's GND or AC coupled.
Is the displayed ripple synchronous with the ripple on the +5 volt
supply?
I believe so, despite the reported frequency on the ground waveform.
They should be the same sweep rate. The latest photo says otherwise,
though.
There's quite a bit of jitter. Is it normal for the frequency in a
switching supply not to be particularly stable?
is the latest photo. Top trace CH1 is the +5 on the side board.
bottom trace CH2 is gnd coupling. I see they are somewhat dissimilar
this time. That's probably because the +5 ripple is on top of the
ripple that gnd coupling has. i.e. this photo is from the problem scope.
(The other two photos disappeared, since this is a family account and
not everybody is in sync.)
I do not think the graticule output circuit will work correctly
without a load. What does the voltage measure with the lamps
connected? Does it otherwise work?
Otherwise? The graticule never lights up. As such, it may not make a
difference whether I connect them. Even more reasons to see what the
good scope does. The two white leads from the graticule light assembly
ohm-out as open. 14.7V or so from the scope.
====
The 0:30 total runtime is due to recent experiments in isolating the DUT
without a true isolation xfmr. One option is to run it off a 12V
inverter. The one I have is entry-level, lacking oomph to run the
scope, and rather non-sinewave. Another option is the UPS I have it
on. Pull the utility power and it's also somewhat non-sinewave, and the
scope didn't like that very much either, losing NVRAM contents, it
seems. Self-test has no results for 7000,8000,9000 tests. A problem
for later, fixable with self-cal.
--
Jeff Woolsey {{woolsey,jlw}@jlw,first.last@{gmail,jlw}}.com
Nature abhors straight antennas, clean lenses, and empty storage.
"Delete! Delete! OK!" -Dr. Bronner on disk space management
Card-sorting, Joel. -Crow on solitaire
