Test Equipment: Oscillocopes

[TinselKoala]

Yes, that little dot (or dots) off to the left, out of view offscreen when screen is properly centered but blanked from a no-trigger condition, is normal. At least both my 2213a and the HP180a do it too.

[Brian516]

Ah, I think i may have figured out the problem... possibly. but it's not so easy for me to verify this....

I have tripped over my power cord/HDMI cord on multiple occasions and damaged the charger port of my computer... and it is now to the point where it rarely actually charges the battery when plugged in.  The computer will run off the AC source, but I have to squeeze around the port and play with it a bit to get it to charge, and it's become really hard to get it to actually charge.   Upon closer inspection, I see that there are in fact two contact points to the outer ring (neutral/ground connector) of the plug, and one, being most likely the ground from the laptop, must have a broken connection from the motherboard.  If I am correct and that is the case, then I have found my reason why I am not getting a solid ground connection between the laptop PSU and the scope.

At some point I will have to take my laptop apart to access the PCB where the port is attached and fix it. I just ordered an original replacement off ebay for $4, so when I get it and replace it I will try again with my laptop and see if that was the issue.  I'm not going to bother trying to fix the one that's in it, so I only have to take it apart once.... going to have to grind down a soldering iron tip to a superfine point for this task. I broke a 30W soldering iron the other day (heater wire broke free from contact) and am going to mod it and make it a 15 or 20W. which would you suggest I go with? my 6-8W is battery op and kinda sucks, and next one up from that is 25W. Also, should I spread out the heater wire, keep it all at the back, or all at the front?  _sorry for the off-topic question_!!)

[MarkE]

Made a vid to show the results of this test. From what I gather from your explanation, for some reason I do not have a ground/common connection from the laptop to scope.  Let me know your thoughts on the matter.   Also, I pointed out that there is a little dot to the left, just off screen when centered, when the scope is in standby mode. Is that normal? Watch vid and then you will understand the pic that I linked to.

https://www.youtube.com/watch?v=jkDdHDRAoyQ

http://i1081.photobucket.com/albums/j347/Brian_Bloom/CAM00254_zpsxtm5ctp2.jpg

It looks like the common is open between the headphone out and the oscilloscope input.

[Brian516]

It looks like the common is open between the headphone out and the oscilloscope input.

If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is.  I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good.  So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?

I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?

I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH

[MarkE]

If what you're saying means that the whole laptop to AC source ground connection being broken doesn't matter, and what matters is the soundcard ground to scope ground, I'm not sure what the problem is.  I checked continuity in the probe's grounds, and they're good, and checked continuity in my headphone cable setup, and they're all good.  So what you are telling me is that either the PCB ground to HP jack ground is broken/not connected, or my scope input connector to machine internal ground is broken?

I checked the continuity between the collars of the BNC and the ground input plug on the face of the scope, and it's good. It's also good from the scope plug ground prong to the BNC collars and the ground connection plug on the face of the scope. So it's back to the PC, correct?

I'm so sick of having problems with stuff!!!! I just want it all to WORK so I can LEARN HOW TO USE IT ALL!!! AHHHHHH

There is a simple test:  Hook your laptop to an AC powered stereo.  If you get a bunch of 60 cycle hum then you have a bad ground connection.  If not, then there is something else going on with your oscilloscope set-up.