Test Equipment: Oscillocopes

[MarkE]

When I have the laptop hooked up to the AC powered stereo unit (with the unit on only stereo mode, no enhancements such as surround, dolby, etc) It works perfectly.  no hum at all.  It plays music without any hum at any volume, without any input from the laptop with the stereo volume up, and with a 1khz sine wave output.

Well when a circuit cannot support DC (the exponential decay in your square waves) and the common is connected, then somewhere a blocking capacitor has been inserted, such as by setting the oscilloscope input to AC.

[picowatt]

Well when a circuit cannot support DC (the exponential decay in your square waves) and the common is connected, then somewhere a blocking capacitor has been inserted, such as by setting the oscilloscope input to AC.

MarkE,

I think we should all just focus on getting Brian to the point where he can get stable, correctly triggered displays on his scope.

A bit of tilt is the least of his problems at this point.

In the last video of his scope in action, I wanted to turn off CH2, speed up the horizontal and adjust trigger level for a stable display.  Looks like he had one of the channels vert. sensitivity cranked up much higher than the other (or different probe factor), horizontal sweep way to slow, and that it was not triggering.  It has been some time since Brian has produced a video of a stable display, tilt or no tilt.

PW

[TinselKoala]

(snip)
I also noticed that when I have it on X-Y with no input and on 5mv/div, it's not just a dot in the center.  If I turn the intensity up a little, I can see what looks like half of the infinite symbol emerging from the dot towards the top of the screen, so more or less a teardrop shape with the point being at the dot.

(where's the 'smashing my head into the wall' emoticon thing??      )
Brian

Do you get that when both channel input coupling switches are set to "ground"? And the scope is fully warmed up, and the "focus" knob is adjusted for the best focus?

If the above are true, then you could try adjusting the "Astig" astigmatism control slightly to see if it improves the shape of the dot, but try to remember where it was set before so you can put it back if you get no improvement.

[picowatt]

Do you get that when both channel input coupling switches are set to "ground"? And the scope is fully warmed up, and the "focus" knob is adjusted for the best focus?

If the above are true, then you could try adjusting the "Astig" astigmatism control slightly to see if it improves the shape of the dot, but try to remember where it was set before so you can put it back if you get no improvement.

TK,

Hopefully his "infinity symbol" goes away when he sets the input switches to ground.  Regardless, I think he should stop tweaking his scope 'till he is a bit more comfortable using it, and actually knows what is and isn't working.

I thought he was able to produce a stable, dual channel display of the calibrator some time ago.  He should get back to that point before moving on.

PW 

[TinselKoala]

Sure, I can agree with that... but I also encourage experimentation when done in an orderly manner, with time to analyze the results of each change in a variable!


Meanwhile... on the issue of improper signal grounds and use of the "LINE" trigger source:

I've just shot another video demonstrating the use of the "LINE" trigger source to find and display line noise (60Hz hum) superimposed on a signal of interest, caused by improper or insufficient signal ground at the scope.  This video will be ready to view in a few minutes.



Meanwhile, slightly off topic, here's my "scoposcopy" video on the basics of determining frequency of a signal using an analog scope, featuring the classic antique Tek RM503 precision low-frequency oscilloscope:

Frequency in Hz = 1/(period in seconds)
and of course
Period in seconds = 1/(frequency in Hz)

http://www.youtube.com/watch?v=teXXF0a_WoI

(Apologies for the poor video quality, this was before I found the right transcoder to use with my camera... )


ETA: The Line Trigger/Mains Hum video is ready here:

http://www.youtube.com/watch?v=spGpBz4K8rU