Test Equipment: Oscillocopes

[picowatt]

I wish I could just get a whole freakin' day to myself to sit here and test everything on this scope so I don't have to keep putting stuff away and taking it back out.  Things would get done a whole lot faster.   
Anyway, I should have the next couple hours at least free to do this....
I have 3 DMMs here and am going to check all the rail voltages. 
I have used page 240 aka section 12 diagram as my reference for the test point to voltage matching.

Do you want me to also check all the rails on low V AC settings for "noise"?   And this noise would be any unstable reading, correct?

I am going to do my best to record all of this procedure. I am first going to record a new vid of the calibrator trace from CH1 and CH2 separately and upload it, so we can get this rolling now that more people are interested.

Thanks for all the help everyone, and sorry it's been taking me so long to get the necessary info out here.

Brian

Brian,

Please do check the supply rails and write down your measurements.  When checking the DC rails with the voltmeter set to AC, anything over a few tens of millivolts is likely indicating a problem.  You may have some noise pickup using unshielded test leads, but just get some rough DC and AC measurements for now (ideally, your AC readings will be close to zero).  Pay particular attention to the 55 volt rail, it is used as the reference for four other supply regulators.  Any noise or problems with that rail will affect the other four that use it as a reference.  Since you've already had the scope on several times, I would not bother with the shutting down between measurements, unless it will take a significant amount of time or difficulty getting to the next measurement point.  Consider using a clip lead to attach your meter negative lead to the supply common so you only need to probe with and concentrate on the other DVM lead.  Be careful probing, don't slip and short something with the probe. If a TP is hard to get to, turn off the scope and use a spring hook or small clip lead to attach your meter to the scope.  Happy hunting, look forward to your measurement results.

I am not sure I would bother making a video of you doing the supply measurements.  If you use a tripod and having a camera on you does not make you nervous or distract you, go for it.  But when working on the scope, you need to focus ONLY on working on the scope.

Can you provide a link to a video that most accurately reflects the current state of or problems the 'scope is having?

PW

[Brian516]

http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan1_zpsyc0entbh.jpg

http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan2_zpshoyjanxs.jpg


Scans of A9 layout.  They didn't turn out too great, but they seem better than the one you posted before.
I had to darken the contrast a bit to get the outlines, and it blurred some of the text.

PW -
here is a link to the most recent video.  About to check it again and see if it's still the same and record that. Also I want to get a visual of channel 2 posted.

https://www.youtube.com/watch?v=C8WUWgIVG0A

Brian

[picowatt]

http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan1_zpsyc0entbh.jpg

http://i1081.photobucket.com/albums/j347/Brian_Bloom/Scan2_zpshoyjanxs.jpg


Scans of A9 layout.  They didn't turn out too great, but they seem better than the one you posted before.
I had to darken the contrast a bit to get the outlines, and it blurred some of the text.

PW -
here is a link to the most recent video.  About to check it again and see if it's still the same and record that. Also I want to get a visual of channel 2 posted.

https://www.youtube.com/watch?v=C8WUWgIVG0A

Brian

Brian,

That video looks like the scope is mostly working.  Does channel two function correctly?  If not, what are its symptoms.  Also, does selecting ALT or CHOP affect the channel one display adversely?

Do not attempt to measure the high voltage for now, you seem to have plenty of it.  Just get some measurements of the low voltage supplies for now (from the 110 volt rail on down).

Is that extreme brightness/blooming just a camera artifact?  I keep wanting to reach for the brightness control and turn it down!

PW

[Brian516]

https://www.youtube.com/watch?v=nMcNEvQ4b4o


Well it appears that everything is working perfectly now.  I guess whatever was wrong was fixed when I removed the trigger/sweep boards and cleaned them up.  There was a decent amount of gunk on the switch drums, so I'd imagine there was a good bit on the finger contacts as well.  I couldn't get a good view of them, but I took a small camel hair brush and IPA and gently cleaned them by pushing the bristles in under the contacts back and forth, and turning the drum to the next setting and repeating.  I also gently wiggled around the transistors and made sure they were fully seated. 
Anyway, it must have been either a bad connection somewhere, or some dust or grime shorting something out or something along those lines....  cuz she works, and channel two works fine also.

I've had 'er sitting here running for the last ten min and everythings fine, so no heat problems either apparently.  Should I even bother to check the rail voltages anyway?

The only thing I see is that there is a wee bit of a wave effect going on with the trace. Don't know if thats to be expected.  Also, call me dumb but I don't know how to get both calibrator traces on the screen at the same time, unless they overlap on analog scopes instead of the shots I've seen of digital scopes where the top half shows one trace and the bottom another.

Either way I'm thrilled it's working and I don't have to replace anything.  good thing I didn't order anything yet!!   Plus, I got my new probes in the mail today, too!

Thanks for all the help!!!  Now I get to learn all of the functions of it!

Brian


Ah.. figured it out.   "CHOP" & "MIX" and then having them on two different V/div settings does the trick.

[picowatt]

Brian,

It sounds like you figured out how to display the two channels at the same time.  Typically you will use ALT most of the time and CHOP for lower frequency signals.

Using your clip leads/wires, short each channels' BNC center contact to ground (BNC collar or the scope's ground lug) and with the channel gains turned up, switch between AC, DC, and GND on the input coupling switch.  The trace should not move up or down while doing this.  Any movement means there is offset in the input amp that needs calibration.  Check the manual regarding this.  You will likely need to switch your trigger source to LINE or switch to "free run" so that the trace appears with no signal applied.

As for the waviness, I assume this video was made with the scope covers on.  If so, there is likely some supply ripple on one of the supplies.  Your scope appears to be working sufficiently to use it to look at its own low voltage rails when you get a probe.  Likely you have a little AC at line frequency riding on a rail, unless the video was made with the cover off.  I have some scopes that will ripple a bit with the lid off.

Do you still get a weirdness when cranking on the trigger hold off?

Congrats, all in all it is looking pretty good.

PW