Dreamcolor Panel Noise

I've recently got my hands on an 8760W DC2, and comparing it with my DC2 8560W, there seems to be an annoying beeping sound from the top right side of the panel (around where the DC sticker is).

It's unnoticeable at normal office work conditions (70-100 cdm2) for the 8560W, but it's more prominent on the 8760W. It varies with brightness and color temperature, plugging into an external monitor or turning the laptop monitor off kills the noise, so it is the monitor. Don't know if it's an inverter, I thought these DC Panels didn't use inverters. Weird thing is, it seems my right ear is much more sensitive to this noise than my left ear.. as when I put either ear to the monitor, I can barely hear it with my left :S.

Anybody else noticed this?

 

We have tested a dozen of DC2 equipped 8760w's and never noticed any noise. When I get back to our lab next time, will check for noise at 100cdm2 and below. Stay tuned.

 

Cool! Thanks a lot. It's worth noting that it is only noticeable in a very quiet working environment.

 

Sure, I'll keep that in mind. Should have some info for you tomorrow.



-- sent from my I B M ThinkPad R40 --

 

no noise. not at work, not at (a VERY quiet) home.

 

No noise here. It's a bit noisy here in our lab though. I can hear a very mild noise coming from the CPU area on the mobo when my ear is 5cm away from the keyboard. But no noise from the lid whatsoever.

 

I have a 8760w with Dreamcolor and Quadro M4000. The display's backlight circuit sure is noisy. In a silent room, I can clearly hear a whine of about 8-10 kHz. Sometimes this can be quite frustrating.

I assumed that this is normal and all DC displays have it? It might be too high pitch for some (older) people to notice, and definetly not audible in normal office environment. Only later in the evening when the office gets quiet, it starts to bother me. The noise amplitude changes with backlight level and user's head orientation.

It would be nice to hear if someone really has a quiet Dreamcolor panel (which I doubt)!

The reason for the noise is probably the large ceramic capacitors in the display backlight leds' dc-dc converter, which is normal for such a design.

 

Hi slintone. Thanks for the reply!

I've noticed recently that the noise is mainly predominant when the laptop is on battery power, although it is still there on AC, it becomes really loud when you're on battery only. Have you noticed this as well?

As for it being normal for such a design, the DC2 screen on the 8740W I own is completely silent.

 

Yes, many things seem to affect the noise. I just tested and I got the same results: the noise went noticeably down when connecting to AC compared to battery operation.

About it being normal or not - I design similar "constant current" power supplies for LED driving all the time. Of course we try to avoid human hearable acoustic emissions from the switching systems. Usually it is a matter of tuning the switching frequency of the circuit above the human hearable range (> 20 kHz). But sometimes, even if this is done, we will get some audible lower harmonics from the ceramic capacitors or other mechanically noisy components.

Personally, I find it very unprofessional to find this amount of audible switching noise on a laptop computer that has cost me over €3k. If I was responsible for this design, I would have taken this back to the drawing board to remove the noise.