T21 - low level "inverter" whine/noise?

[g8tzl]

I have a low level "inverter" whine/noise on my T21 - I can hear it more or less all the time except when the processor is busy ( I think) - although it's at a low level.

I have recently replaced the HDD and installed XP SP2 (except IE7).

I speaker is disabled.

I originally thought it was coming from the modem. But I did some searching on Google and found a few mentions about inverter noise.

Basically , it was suggested that the inverter whine was a function of load and temperature. By changing the load , the inverter whine could be made to disappear. One suggestion was to play a song on Windows Media Player in the background with the speaker disabled.

So I tried using Windows Media Player and it WORKED - no more whine as long as a song was playing.

Anybody know of any proper fixes. Maybe I should update the BIOS? Maybe its something to do with the Thinkpad Power Management. When I installed XP SP2 , the Thinkpad PM Device driver was missing. Windows XP Update feature actually identified this driver was missing (together with a couple of other "optional" IBM/Lenovo updates). Would a missing Thinkpad PM Device cause inverter whine?

Any other thoughts?

Thanks

[rkawakami]

From your description of the whine changing with relation to the processor work load, then I'd say you are NOT looking at the whine originating from the inverter. Rather, there is probably an inductor on the motherboard that is "singing". I verified this with the T23 I'm using. It has a barely audible whine when running just Firefox. Turning the screen off via the Fn+F7 key does not eliminate the noise, neither does the Fn+F3 combination. Running Windows Media Player with all volume levels down and the speakers muted DOES quiet the noise. But so does running a program like PowerDVD from the hard drive. About any constantly running program would probably change the power being consumed by the processor and affect the inductor. On the T23 the inductor is located adjacent to the CPU. The T21 motherboard appears to have one on the opposite side of the board from the CPU socket. There's not much you can do to eliminate the noise beside replacing the inductor. It might be possible to keep the coil inside the inductor from vibrating by packing it with hot glue, but I've never actually tried it.

This is not to say that the inverter can't make any noise; it can. If the whine IS coming from the inverter, then you should be able to change the pitch/volume by changing the backlight intensity. Use the Fn-Home and Fn-End keystrokes and see if you can hear any difference. The inverter can sing because it has a similar component to an inductor (a transformer).

ref: http://forum.thinkpads.com/viewtopic.php?t=47660 (T21 motherboard; see bottom side C7/C8 )

[g8tzl]

Ray - Thanks for the excellent overview.

I tried changing the backlight intensity and it made no difference to the whine - so it looks like its the inductor "singing".

I don't think I've ever noticed it on my T30 , 570E and 600E.

Is a singing inductor common with the T20/T23's? Do they all sing?

I also noticed that my T21 also seems to have the modem speaker enabled by default - so I can hear the modem loudly "whining" when the speaker is enabled. Again I've not noticed this with the T30/570E/600E. However, I think I can easily disable the modem speaker in Modem Properties

Thanks

[rkawakami]

I wouldn't say that all T2x systems emit noise... I think that out of the collection of T21, T22 and T23s that have been in my possession, only two or three of them (~8%) have had any noticeable problem with inductor/inverter noise.