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U1620A Fan Noise Issue

Question asked by glowitz on May 8, 2014
Latest reply on Jun 23, 2014 by jeff002

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I just received a new U1620A scope from Agilent. After power up, the fan sounds noisy and erratic...like it is not balanced or scraping against some plastic. if I simply rotate the scope slightly, the noise gets worse or slightly better. It sounds like a faulty fan out of the box. Does anyone else hear a warbling pitch. I'm not talking about fan noise with consistent whirring but more like a rattling or grinding sound that doesn't exude Agilent quality. Just trying to figure out if this is normal or faulty before I send it back. I'd love to hear from other owners what they hear with their fan. I do have a call into the reseller and Agilent but no clear answers just yet. Thanks.

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totog Jun 11, 2014 7:21 AM
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Hello,

i bought U2702 scope and i heard this horrible sound ;)
I open the back cover of scope and put 2-sided scotch-tape between top of fan and framework.
Now it sounds much quiter. This little fan works well, but it's noisy.
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- glowitz @ totog on Jun 11, 2014 11:03 AM
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  Of course, these are two different products and I'm not sure if they use the same fan or not. But you raise an interesting possibility that the fan could be vibrating against the case due to a slight tolerance variation somewhere. Since it was a new unit, I didn't want to open it and possibly void the warranty.
  
  That said, I sent my unit back to Agilent after their service personnel agreed this wasn't right. It's been over a month waiting for a fix, and apparently they had to order a new unit which should arrive this week. Apparently I'm not the only one with this issue, so hopefully it's something that Agilent will address in production.
  
  Hopefully the new one sounds better :-).
  
  In summary -- if anyone owns an Agilent U1620A (or similar scope model) -- and you hear a noisy fan, you'll now know this is not normal. It seems that the standard repair method for this unit (and possibly other handheld products) is a product swap, as there are very few internally repairable assemblies other than possibly the display, battery, etc.
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  - jeff002 @ glowitz on Jun 20, 2014 11:22 PM
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    Did you get it back? Is the noise gone?
    
    I have the same problem with my scope. I got an authorization to return it so I bought a second scope. This one has slightly louder noise that changes as the unit is rotated, exactly as you had described.
    
    I wonder if all scopes are like this? I called Agilent Tech support and was told this is not normal. What's going on with Agilent quality? Is there anyone out there without this problem?
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    - glowitz @ jeff002 on Jun 21, 2014 12:16 AM
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      Hi Jeff,
      
      Interesting to hear that you're having the same issue. Yes, I just received the unit back a few days ago and have some updates that may be helpful.
      
      1) The new unit is definitely improved over the first one when using the tilt-out stand. It's still a bit noisy for my taste for a handheld type device, but I accept it for what it is.
      
      2) That said, when I do lift it up and rotate it in the air, the fan noise gets louder and softer depending on the orientation. You might think it could be gravity pulling on the fan in different ways -- but even just a very slight tilt can cause a step function increase in the noise. To me, this seems unusual (at least in my experience).
      
      3) Since my new unit arrived and had Aglient calibration stickers on it, I didn't want to void the warranty to open it up. So Agilent graciously provided an image of the inside so we can better understand potential sources of vibration.
      
      4) If you refer to the photo, the fan does not rest against the upper or lower case. It's recessed into the bottom portion and secured to the PCB. So this probably rules out a scenario where the fan is touching the case.
      
      5) However, notice there is what appears to be a black grounding cable connecting the top and bottom clam shells. The bend of the black cable has to go somewhere when you close it up. Where do you think it goes? Although I can't see inside the box when it's all buttoned up, it appears from this photo that the bend of the cable would be positioned just above the fan blades. I can't tell for sure how much vertical gap there is, but it is certainly "feasible" that the cable could be touching the top of the fan housing and/or interfering slightly with the airflow around the fan. If you think about it, tilting the unit could change how the cable and fan interfere and might explain the variable noise depending on the tilt of the scope.
      
      6) There is also another set of power cables (the black and red cables) that are likely the power for the fan -- and I suppose it's possible that those cables are vibrating between the side of the fan and the paper or metal shielding that I see to the right. The cables just seem to be floating in place and could easily move around a bit.
      
      7) In an email exchange with the Malaysia facility, they stated that they do check the fan noise as part of the inspection process -- at least a quick check. There may not be any "spec" for this -- and it could be that in the position they test it, they don't hear any noise. But I can image that it's probably a noisy environment with other test equipment around so it may be difficult to hear the fan noise independent of other ambient noise in the facility.
      
      In summary, my new unit is better, but still not what I would expect for a several thousand dollar Agilent scope. I'm hoping that with enough good ideas here we can get to the bottom of this. But right now, the most logical culprit could be the cables interfering with the fan somehow -- and this is affected by tilt angle. It would be a very easy test to try by rerouting the cable out of the way and/or securing it so it could not ever touch the fan blades or case (or even be in the way of the airflow, which could cause it to vibrate like a reed). I just don't want to open mine up at this point and risk breaking something. But certainly Agilent could try this and see if it makes any difference, particularly on a returned unit that's noisy.
      
      I will say that the Agilent service team has been very responsive and I appreciate that. Sometimes it's difficult to get a real person to communicate with you who is actually familiar with the product. In this case, I requested to speak directly to the repair technician in the US and she was extremely helpful. Through our communication, she was able to get more information from the factory about the fan (as well as another vertical noise floor question I had). That said, given that you also have an issue with a noisy fan, then it's clearly not an isolated situation....either that, or most people don't care to report it or just use it on the bench and don't notice as much.
      
      I hope that the Malaysia factory will read this thread -- and consider the possibility that the cables could be the cause -- or at least rule those out as possibilities. It may be that these fans have mediocre mechanics and are optimized for cost rather than noise.
      
      It's expensive for Agilent to be swapping units due to noisy fans -- so I hope that they will get to the bottom of this and report back on their findings. It might be fixable with a very minor improvement to the cable dressing and positioning. But that's purely speculation until an engineer can definitively prove it one way or the other.
      
      If anyone out there has the same issue -- please chime in -- and if you're willing to open up your unit, maybe you can try repositioning the black cable shown and rule out any interference with the fan blades or air flow.
      
      See attached photo
      
      Good luck!
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      U1620A-fan.jpg261.4 KB
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      - jeff002 @ glowitz on Jun 23, 2014 12:47 AM
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        Hi Glowits,
        Thank you very much for the picture and your detailed response. Initially, I thought the fan blade might be touching the fan case but that's just another speculation. The fan noise on the first unit definitely gets lower after about 5 minutes once it warms up, almost to what I would consider an acceptable/reasonable level (just fan noise that doesn't sound like blade is touching something).
        
        Just like you, I wish I could open this up but for the same reason you have stated, I don't want to do that.
        
        The second unit is slightly worse than the first one so I will be returning the second one for sure, and think about what to do about the first unit. I will call Agilent today and discuss again. The person I spoke to at Agilent was also outstanding. He called someone on the business side, who in-turn, called Newark to authorize my return, while I was still on the call.
        
        I was not pleased with Newark's return policy. As I found out, you can return an equipment for full refund if there is nothing wrong with it. But if there is a defect, it has to go to warranty repair and they will not normally give your money back. The guys at Agilent arranged for full refund so I purchased another one, which unfortunately has the same problem.
        
        So what are you going to do? Keep the scope?
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        glowitz @ jeff002 on Jun 23, 2014 9:16 AM
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        Jeff,
        
        A few points...
        
        1) You are fortunate that you got an authorization to return one of the units to the reseller. In my case, I checked with our reseller and they had no inventory and was told I would have to process it through Agilent's Warranty. In my case, what originally was supposed to take about two weeks took about one month, not to mention about $50 out-of-pocket in postage and insurance to return it, even though it was DOA. I later learned that typically these units are swapped, not repaired -- and so Agilent had to order a new one from the factory in Malaysia -- and basically I waited again in the queue. I was then told (after about one month) that there would be another delay (maybe up to 2-4 weeks). Needless to say, I wasn't happy about the prospect of being without the unit for 1-2 months, particularly after I waited 5 weeks for delivery of the first unit, which was on back-order. At that point, I escalated my repair ticket and Agilent was able to allocate a unit to me, which shipped within a few days of my escalation.
        
        Given the excessive repair delay, I requested that the warranty clock be reset, which they also did. Again, an example of a good company making good on a quality issue, so I'm appreciative.
        
        2) As to whether I'll keep this one or not, at this point, I do need the scope and I plan to keep it. That said, I'm still less than satisfied with the fan issue. I was using the scope over the weekend and the fan noise was really variable. Sometimes just sitting perched using the integrated stand -- the fan would get noisier then less noisy. Even just moving the position slightly or a few degree change in tilt would cause it to vibrate/rattle more. In my case, I never just hear what I would call a "soft whirring" of the fan. It always sounds a bit "vibratory" as if something is touching the fan blade (or vibrating nearby). I'm still suspicious of the black grounding cable or the adjacent fan power cable and whether there could be a condition there that causes this noise due to some proximity of the fan with those cables. Although this doesn't appear to affect the operation of the unit, it just doesn't exude the kind of Agilent quality that you'd expect from a product that costs several thousand dollars. I still hope that the Agilent engineering team looks into this to get to the bottom of it.
        
        If it turns out that nothing is vibrating inside the case (e.g. cables, etc) and it is just the way the fan itself is built, I would invest another dollar or two to find a better fan that doesn't have this issue. In the long run, customers will be happier, with fewer returned units (which is otherwise very expensive for all parties), and the impression of the quality of the unit will go up. There is also an interesting psychological effect. If the unit "sounds" broken or marginal, then you tend to distrust the measurements too. I realize it's not logical -- but quality (good or bad) creates an aura around the product that transcends any one issue and you begin to question other things about it with a more critical eye.
        
        It's also possible that there is a bad batch of fans or that there are multiple suppliers for this part. And since these are being tested in a production environment with lots of other test equipment, the production people may not even realize (or hear) the fan noise as it would be masked by the surrounding test equipment. But when used on a workbench or while standing at an electrical panel with low ambient noise, then the fan noise is much more obvious.
        
        If you also point your Agilent support person to this thread, perhaps we can get someone at the factory to take a more serious look at this and not dismiss it as a non-issue. If some customers (like us) are noticing this issue with multiple units, then it's certainly worthy of further exploration. It may not be their top issue, but its one that should be resolvable I would think. At some point, I may just open mine up and try to dress the cables differently to see if that helps. It's not what I want to do, but I don't want to keep swapping units with Agilent to find a "good one" until it's understood definitively what's causing the variable fan noise.
        
        Please keep us posted on your situation so we can all learn and share the latest. If I can figure out a way to make a quality audio recording, I might try that. I tried it once using my iPhone, but it didn't come out too well. I'll have to come up with something else...
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        ksmith @ glowitz on Jun 23, 2014 3:29 PM
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        All,
        
        It seems there are at least a handful suffering the fan noise problem.
        
        The ones we have “here” are whisper quiet. I cannot hear anything form them unless I put my ear right up to the rear panel.
        
        These should be returned to the authorized Agilent Distribution partner from whom you purchased the oscilloscope as an “Out of Box Defect” (OBD) IF the unit has been delivered in less than 60 days. You can find a list of authorized distributors here: www.agilent.com/find/distributor Have them open the unit up and power it on to see if it is noisy or not before sending out a new unit. If there is no stock, then the distributor is supposed to re-order one, but often that is longer than the time to repair. The turnaround time on a repair is typically 2 weeks. If it is past 60 days since it was delivered (or re-ordering will take longer), they can be repaired under warranty (these, and everything else from Agilent’s electronic measurements group that has an SN now has a 3 year warranty standard). You can check your warranty here: www.agilent.com/find/warranty You will need to call your local Agilent business center. You can find this info on the @ www.agilent.com/find/contactus, being sure to set your location correctly. The turnaround time on a repair is typically 2 weeks.
        
        Agilent will be looking into this problem. Please do not expect any updates via the forums, though.
        
        Disclaimer: For more reliable response, you should consider calling your local Agilent Technical Call Center. The Agilent Forums are monitored on an "as available" basis, and aren't necessarily the fastest way to get technical questions answered.
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        glowitz @ ksmith on Jun 23, 2014 10:43 PM
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        Thanks @ksmith.
        
        I've followed all your suggestions (working with the Agilent support team) but am reluctant to return it again until a definite engineering assessment is made and implemented (assuming something is found to be defective). For reference, I'm posting a 30-second audio clip so we can all hear the same thing. This will help to reduce subjective descriptions of what it "should" sound like. My new unit, which is better than the first one, sounds like this: https://buildera.box.com/s/zxt37bn4mb00n405k2b2
        
        I recorded this with my iPhone, so the audio isn't very loud. Please adjust your speaker volume for this clip. For reference, the SN is MY54220029.
        
        During this 30-second clip, I am holding the unit in my hands (both hands) with the iPhone microphone nearby -- so it's not vibrating on any surface. This is in the air. I rotate the unit at different angles and speeds and then hold it steady....then rotate, etc. Maybe this helps a little so we all hear the same thing.
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        jeff002 @ glowitz on Jun 23, 2014 10:21 PM
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        That's what my scope's fan sounds like.
        
        Kevin, I spoke to you on the phone last week. Thank you for your assistance. Everyone at Agilent has been just fantastic but this product has been a disappointment.
        
        I had always marveled at how well HP/Agilent test equipments work over the years, always performed much better than specified accuracy. For example, my Agilent spectrum analyzer's is so accurate that I could almost use it as a frequency standard. If the spec was 1ppm, it performs at 0.01ppm. My HP8656B signal generator is still perfect and it's almost as old as I am.
        
        U1620A is the first Agilent product that I regret purchasing. Beside the fan issue, it picks up a lot of ambient noise. For example, if I set the vertical scale at 20mV/div and bring the scope close to any electronic devices such as printer, computer LCD monitor, it picks up 120Hz spikes (~50mVpp) even without any probes attached.
        
        I hope this is not indicative of what's to come with Keysight Technologies. I did not want to do it but now, I am considering buying Tek THS3000.
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        jeff002 @ glowitz on Jun 25, 2014 11:58 PM
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        Duplicate response deleted.
        
        Edited by: Jeff002 on Jun 26, 2014 12:57 AM
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        jeff002 @ glowitz on Jun 25, 2014 11:59 PM
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        Duplicate response deleted.
        
        Edited by: Jeff002 on Jun 26, 2014 12:58 AM
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        jeff002 @ glowitz on Jun 25, 2014 11:59 PM
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        Duplicate response deleted.
        
        Edited by: Jeff002 on Jun 26, 2014 12:59 AM
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ksmith Jun 23, 2014 3:17 PM
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(duplicate post)
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U1620A Fan Noise Issue

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