RIGOL 1052E capture behaviour question

[hozone]

Hi all,
I've the RIGOL 1052E, no mod, original 50Mhz.
I'm trying to repair a synthetizer board based on the mc68331 MCU.
I'm checking the CLKOUT of this IC, which with my 32.768 kHz crystal should output 8.389 MHz, it does't.
Here comes the quotion about the behaviour I've notice on my RIGOL.
If I capture (Run/Stop) CLKOUT at something less than 100.00ns I see a 25.1655Mhz output, even if I zoom out, it stays the same.
If I do the same thing with more than 100ns, the capture shows a non linear output.
Find some image as reference.
Why does this happens? Sorry for this dumb question.
I even try with my logic analyzer (https://sigrok.org/wiki/VKTECH_saleae_clone), see attached image. But I'm not sure if this reading is wrong cause it goes up to 24Mhz max logic analyzer speed, or this read is right.

Thank you!

By the way the repair thread is here, I'm still working on it, ordering some parts https://www.norduserforum.com/nord-lead-rack-forum-f12/nord-lead-3-problem-does-not-boot-t20997.html

[tautech]

Do you understand what the little orange T arrow is for ?
It indicates the trigger position in you case is 300ms to the left of the display and therefore everything you see on the display is post trigger.
Press the H Pos control and it should return the trigger position to 0s; the middle of the display.

[hozone]

Thank you @tautech
I've not notice my trigger was out today, I was experimenting and I forget this out. The last days when I notice the behaviour the trigger was centered.
By the way, things does not changed, see images. The 50ns zoom out is missed, but the cure has same Vpp all the way.
Also I post the image with 1ms time internal, notice the zoom signal.
I'm sampling in DC, RealTime, MemDepth normal.
thanks!

[Fungus]

I'm checking the CLKOUT of this IC, which with my 32.768 kHz crystal should output 8.389 MHz, it does't.
Here comes the quotion about the behaviour I've notice on my RIGOL.
If I capture (Run/Stop) CLKOUT at something less than 100.00ns I see a 25.1655Mhz output, even if I zoom out, it stays the same.

The screenshots look OK, right now I'd believe the oscilloscope until proven otherwise.

Do you have anything else with a known clock in that frequency range? Take a look at it.

[hozone]

Hello @fungus,
Think you got it.
I've test it with my func gen, see attached images for 3Mhz.
It seems the problem persist till 100Khz at least.
If i capture at 50ms the zoomed signal is a mess. At 20ms no problem.
Also notice the difference of zoom at "zoom 0" between 20ms and 50ms. That's something happeneing...
Also for reference my RIGOL softwre version.
Time to update to 100Mhz mod?

[Fungus]

If i capture at 50ms the zoomed signal is a mess. At 20ms no problem.
Also notice the difference of zoom at "zoom 0" between 20ms and 50ms. That's something happeneing...

The 'scope might be lowering the sample rate when you change the time base to 50ms. That would cause aliasing with result like you're seeing.

Sample rate is usually displayed on screen on modern scopes but I can't see it on your screenshots.

[hozone]

Thank you! That's sounds what I'm looking at.
I've search a little bit, thanks to your information I've found this https://www.eevblog.com/forum/projects/rigol-ds1052e-nasty-bug/
Long Depth memory mitigate the problem.
Now I can investigate further on my repair, later I'll check with the CLKOUT of that MCU