Test Equipment: Oscillocopes

[TinselKoala]

I would strongly advise against that.  If there are little trim pots all over the boards in your scope that typically means that the boards had to be tuned and aligned with the trimpots as part of the manufacturing process.  Changing a cap could adversely affect the tuning and alignment of your scope.  I am being cautious and very generic in my statement.

I think this is unlikely in this case. Take a look at the schematic to see the function of these tantalums in the circuit.

[picowatt]

I think this is unlikely in this case. Take a look at the schematic to see the function of these tantalums in the circuit.

TK,

Where is a video of the current state of this scope?  Last one I saw was with severe blooming with what looked like horiz scan issues.  Is there a newer video showing the scope functioning a bit better?

Has Brian posted any DC measurements of at least the LV rails?  'Tis the best place to start.

I doubt that tant is the only +5 rail decoupling cap, but if it is noisey, it might be glitching the line.  Temporarily replacing it with an electrolytic or even just attaching one across the rail may assist diagnostics.  In the absence of a scope for diagnostics, MH's suggestion of looking at the 5V rail with a voltmeter set to low AC volts might be revealing if the rail is glitching/noisey.

C1476, is that it in your parts layout to the left of the number "89" arrow.  If it is, it looks fairly skinny on the drawing you posted.  What board is that on?

Which cap does he state has the lead arced open and on what board is that cap?  A burnt/arced off lead sounds like a smoking gun.

PW

[TinselKoala]

TK,

Where is a video of the current state of this scope?  Last one I saw was with severe blooming with what looked like horiz scan issues.  Is there a newer video showing the scope functioning a bit better?

I think the blooming is just the intensity setting up too high. The scope produced a "perfect" image of the calibrator trace on CH1, but had some strange periodic glitch, like half a second interval, of a sharkfin-type trace that looked like it might be on the unblanked return of the beam.

Has Brian posted any DC measurements of at least the LV rails?  'Tis the best place to start.

No, not to my knowledge yet. I also have been asking for these, and I found in the manual which the testpoints are and the voltages/tolerances for them.

I doubt that tant is the only +5 rail decoupling cap, but if it is noisey, it might be glitching the line.  Temporarily replacing it with an electrolytic or even just attaching one across the rail may assist diagnostics.  In the absence of a scope for diagnostics, MH's suggestion of looking at the 5V rail with a voltmeter set to low AC volts might be revealing if the rail is glitching/noisey.

Yep.

C1476, is that it in your parts layout to the left of the number "89" arrow.  If it is, it looks fairly skinny on the drawing you posted.  What board is that on?

Which cap does he state has the lead arced open and on what board is that cap?  A burnt/arced off lead sounds like a smoking gun.

PW

That is the one, C1476. It is on the A9 interface board. See the schematic excerpt below, from p. 228 in the pdf SM.


ETA:  http://www.youtube.com/watch?v=C8WUWgIVG0A

[picowatt]

TK,

If it was me, besides already knowing the rail voltages, if I suspected the caps that are highlighted, I would temporarily replace them with something from my on hand parts bins.  The two tants in question could be replaced with 47uf at anything over 10V electrolytics and that ,1uf ceramic with any ceramic of similar or greater uf and voltage rating should work OK as well (I think I would stay under .47uF).  it would at least help identify if those are bad caps.

You say one channel actually shows the calibrator signal OK?  I would think a problem with the highlighted caps would affect both channels.

Maybe you or Brian could post a link to the video of the calibrator signal.  I thought things got worse after he cleaned the scope.

PW

[Brian516]

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