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3000X & 4000X acoustic noise?

Question asked by paulstoffregen on Dec 19, 2012
Latest reply on Jan 3, 2013 by paulstoffregen

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I'm curious if there are any specs or info on the acoustic noise produced by the various 3000X and 4000X scopes?

I intend to buy a scope for use in a very quiet room. To become more familiar with the 3000X, I recently rented a DSO-X 3014A. So far, I love the scope's features, but it's terribly noisy! I temporarily stalled the fan by poking tweezers through the slot, and it turns out much of the noise is a terrible hissing/sizzling that sounds like a switching power supply is dying.

On Dave's eevblog forum, someone pointed me to a service note documenting this problem. I'll try to attach the file. Tomorrow I'll call the rental company to see if they can exchange it.

So I'm left with a really mixed opinion... I love the 3000X speed and performance, but this **** thing is terribly noisy. Even without the power supply problem, the fan is far too loud for an extremely quiet room. It's really a deal breaker for me.

Perhaps the 4000X has a quieter fan? Hopefully it's also free of audible switching power supply noise? I looked over the datasheet but didn't see any specs about acoustic noise. Is there any such info?

I suppose replacing the fan would void the warranty? I've done that on other equipment, like a cheap Rigol scope that's been on my desk, but at only $800 it's hardly the risk compared to voiding the warranty on a $10K+ piece of equipment.....

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DSOX3014A-03.pdf212.4 KB

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Coris May 4, 2016 11:12 PM

The acoustic noise in the scope may come also from the display PSU. You can try to follow the modification in the note issued by Agilent it self. That circuit showed in that note is also very noisy in high frequency spectre (EMI). You can get some more informations about those aspects from my thread https://community.keysight.com/message/14924#comment-14924
BTW, you do not void any warranty if you open the box and change that noisy fan with another low noise one. The scope enclosure is not sealed (as I experienced my self with my device).
Is just regrettable that Agilent have not yet addressed those issues in theirs devices....

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paulstoffregen @ Coris on Dec 19, 2012 2:13 PM

I called the rental company. They're sending a replacement scope overnight.

This scope appears to be an early model that has a (now) well documented bug. Agilent certainly seems to be handling this well. I've seen your other threads, and it's unfortunate you had such a bad experience through an unscrupulous dealer.

With the obvious caveat, this is an early model scope with a documented defect, here are a couple captures of the noise, with channel 1 shorted. It looks like there are several mV spikes every 4 us, in bursts that repeat approximately every 95 us.

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scope_6.png36.6 KB
scope_5.png28.5 KB

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Willco788 @ paulstoffregen on Dec 19, 2012 9:09 PM

I have very sensitive microphone that hears switching power supply acoustical noise very well. I have selective hearing loss and when a customer complains of power noise, I use my microphone setup and my DSOX3024 to display the noise. Here are my results.

The first image is my DSOX3024 with the micropohone pointing into the air vents just above the power cord
The second image is a customers 200 watt power supply with the microphone 6" away. The power supply case was removed the load was about 24 watts.

Edited by: Willco788 on Dec 19, 2012 10:08 PM

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switcher_noise1.bmp1.2 MB
switcher_noise2.bmp1.2 MB

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paulstoffregen @ Willco788 on Jan 2, 2013 5:52 PM

Just a quick followup... the rental place replaced the scope. The new one is much quieter, but still the noisest thing in the room. The electrical noise/spikes protblems are gone.

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Coris @ paulstoffregen on Jan 3, 2013 1:34 AM

I can recommend that you buy an low noise fan and replace that original (noisy) one. The enclosure of the scope may not be sealed by Agilent (bat it may be by the rental company...). This changing is quite easy to be done. Before returning the device to the rental company, you can put in back the old fan... So, you can have the quiet you need in the lab while you will use that rented scope...

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paulstoffregen @ Coris on Jan 3, 2013 6:05 AM

They already throught of that! This scope has numerous stickers from the rental company identifying it a rented equipment. Several are located at seams or other places requiring removal to open the unit.

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6 Replies

Coris May 4, 2016 11:12 PM
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Correct Answer
The acoustic noise in the scope may come also from the display PSU. You can try to follow the modification in the note issued by Agilent it self. That circuit showed in that note is also very noisy in high frequency spectre (EMI). You can get some more informations about those aspects from my thread https://community.keysight.com/message/14924#comment-14924
BTW, you do not void any warranty if you open the box and change that noisy fan with another low noise one. The scope enclosure is not sealed (as I experienced my self with my device).
Is just regrettable that Agilent have not yet addressed those issues in theirs devices....
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- paulstoffregen @ Coris on Dec 19, 2012 2:13 PM
  Mark Correct
  Correct Answer
  I called the rental company. They're sending a replacement scope overnight.
  
  This scope appears to be an early model that has a (now) well documented bug. Agilent certainly seems to be handling this well. I've seen your other threads, and it's unfortunate you had such a bad experience through an unscrupulous dealer.
  
  With the obvious caveat, this is an early model scope with a documented defect, here are a couple captures of the noise, with channel 1 shorted. It looks like there are several mV spikes every 4 us, in bursts that repeat approximately every 95 us.
  Attachments
  - scope_6.png36.6 KB
  - scope_5.png28.5 KB
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  - Willco788 @ paulstoffregen on Dec 19, 2012 9:09 PM
    Mark Correct
    Correct Answer
    I have very sensitive microphone that hears switching power supply acoustical noise very well. I have selective hearing loss and when a customer complains of power noise, I use my microphone setup and my DSOX3024 to display the noise. Here are my results.
    
    The first image is my DSOX3024 with the micropohone pointing into the air vents just above the power cord
    The second image is a customers 200 watt power supply with the microphone 6" away. The power supply case was removed the load was about 24 watts.
    
    Edited by: Willco788 on Dec 19, 2012 10:08 PM
    Attachments
    switcher_noise1.bmp1.2 MB
    switcher_noise2.bmp1.2 MB
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    - paulstoffregen @ Willco788 on Jan 2, 2013 5:52 PM
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      Correct Answer
      Just a quick followup... the rental place replaced the scope. The new one is much quieter, but still the noisest thing in the room. The electrical noise/spikes protblems are gone.
      Like • Show 0 Likes0
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      - Coris @ paulstoffregen on Jan 3, 2013 1:34 AM
        Mark Correct
        Correct Answer
        I can recommend that you buy an low noise fan and replace that original (noisy) one. The enclosure of the scope may not be sealed by Agilent (bat it may be by the rental company...). This changing is quite easy to be done. Before returning the device to the rental company, you can put in back the old fan... So, you can have the quiet you need in the lab while you will use that rented scope...
        Like • Show 0 Likes0
        Actions
        paulstoffregen @ Coris on Jan 3, 2013 6:05 AM
        Mark Correct
        Correct Answer
        They already throught of that! This scope has numerous stickers from the rental company identifying it a rented equipment. Several are located at seams or other places requiring removal to open the unit.
        Like • Show 0 Likes0
        Actions

3000X & 4000X acoustic noise?

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