Agilent oscilloscope MSO-X 2012A audible high pitched sound and hiss

[mark41]

Hi folks!

I've got a problem with my scope which is really pissing me off! I only found one comment about that problem at keysight's forum but that was solved by giving a new unit to the costumer. I have no waranty with my scope. So...

The high pitched sound is audible since the start of the unit - to be precise - it's connected with display LED backlight (when I disconnect the backlight, it's volume is almost impossible to hear). The sound is increasing in volume and reaches stable maximum after about 5min. Unfortunatelly it's not audible on the video I took. I also found something strange. When I touch the caps above the coils with a probe (that isn't connected anywhere) it starts doing funny hissy noises like tuning a radio (adding capacitance?) and also when I touch hard with my finger the top enge of the pcb and the middle coil with my thumb (showed in the video) the high pitched sound stops completely! Any suggestions/help? It really drives me crazy. Thank you!

Video - in first 5sec you can how camera's focusing sound is like, unfortunatelly the high pitched sound that I talk about is not hearable...which is there from the beginning of the video

[trevwhite]

I would contact Keysight as their customer support is really good. Even if it is out of warranty you never know, they might sort something out.

[Pinkus]

I do not know if your hissing is caused by the same problem. But you may give it a try:
Read this: http://cp.literature.agilent.com/litweb/pdf/DSOX3014A-03.pdf

[mark41]

Thank you!!  I will look into it deeply tommorow.

[mark41]

Unfortunatelly, the pcb layout really differs, so there's no use. However I was digging in the internet the whole morning and tried putting my model and SN to Keysight webpages and voilà service note for my scope! And it suits to my video as well.  I am going to order that inductor and hopefully I'll be lucky next week.

[fanOfeeDIY]

Typically the hissy high pitch noise from inductors are caused when the current flow the inductors and vibration frequency becomes in the hearing range.

It is not recommended solution, but often time, it could be solved by gunk the inductors with hot glue gun or some elastic material.
Then the vibration frequency goes out of the hearing range.

[Keysight DanielBogdanoff]

I fully expect that replacing the inductor will fix it.

[HighVoltage]

Thanks for the link to the Service Note...

I did not know that the service guide is available for these 2000X and 3000X scopes
http://cp.literature.agilent.com/litweb/pdf/75019-97039.pdf
Just too bad there is no schematics inside.

[Pinkus]

it is also available as a Keysight branded version:
http://www.keysight.com/main/redirector.jspx?action=ref&cname=EDITORIAL&ckey=2032052&lc=ger&cc=DE&nfr=-32542.1150190.00
I am just mention it, as it is a newer version. But beware: as the Keysight version has less pages, the Agilent branded version might show additional information (I did not check for any difference; I am keeping both versions on my hard drive in case I ever need it).

[Hydrawerk]

I fully expect that replacing the inductor will fix it.

I have the same problem with my scope, but the hiss sound is rather quiet. Can this develop into a major failure of the inductor? Is it necessary to replace it when I do not care about the weak hiss sound?

BTW I mentioned this little problem in March 2015. https://www.eevblog.com/forum/reviews/my-new-toy-)-agilent-dsox2002a-sex-on-a-stick!/msg619692/#msg619692

[mark41]

Sorry that I havent replied for a long time. I ve been busy with university studies. YES, when I changed the inductors and removed the resistors the hiss is now completely gone... 

[Keysight DanielBogdanoff]

Sorry that I havent replied for a long time. I ve been busy with university studies. YES, when I changed the inductors and removed the resistors the hiss is now completely gone... 

Awesome! Thanks for following up!

[kawal]

Can anyone provide the specs for the  68uH inductors (9140-6151 (68 uH)) ?  What footprint / frequency / amperage is  needed.  Thank you
Maybe someone has a non HP part number.

I was thinking  one of these would be OK

SRR1050A-680Y    which is a 10mmX10mmx5mm part rated for 1.6A
710-784771680     which is a 12mmx12mmx6mm part rated for 1.8A

Thanks

[rernexy]

8 years after the service note was released, I've done the change to my MSOX3054A. It certainly solves the hiss

I did a terrible job removing the 1R0 resistors, as the photo shows. After removing as much of the solder as I could, I used side cutters to violenty cut-crush them off. I'd had enough at that point 

The inductors I used were these by Coilcraft:
MSS1038T-683MLB https://www.coilcraft.com/en-us/products/power/shielded-inductors/ferrite-drum/mss-mos/mss1038t/mss1038t-683/