Thinkpad noise when changing the brightness level

[atomba]

Hi all,
I have been using thinkpad t23 for almost one year. Im maximally satisfied with this "old" notebook and haven't had any problem so far. However, there is one thing that makes me little bit nerves: wink: If I decrease the brightness from the maximum level to any of the lower levels, very unpleasant noise occurs. It comes out of the right upper corner of the keyboard or right bottom side of the LCD.

Does anyone of you have the same experience? What do you think might be the root cause?

Thanks for your opinions!

[dsvochak]

In order to make a guess we may need more information. I assume you're using the Fn-Home Fn-End keys to adjust brightness.

What kind of noise are you getting? Is it static, a whine etc?

Does the noise occur only when you're holding down the keys? That is, can you adjust the brightness to the desired level, release the keys, and the noise stops?

Does it occur with both the Fn-End and Fn-Home combinations?

Have you recently taken anything apart (keyboard for example)?

What happens if you take the Ultrabay device out and adjust the brightness? Do you still get the noise?

What happens if you just hit the Fn key? or the Home, End, PgUp, PgDown keys?

Does Fn-PgUp turn the thinklight on and off? Do you get the noise with this combination?

[ambientscape]

I had the same problem with you, dude!! The problem comes from the LCD...... If you were to use it in normal environment...its ok. You will notice it in a very quiet environment.....If your thinkpad is still under warranty...bring it for repair. I'm not bother to bring mine to repair because i used it everyday.....and the problem is not that major.

[atomba]

Thanks guys for the reply!

To dsvochak:
Yes Im using Fn-Home,Fn-End keys to adjust the brightness. The noise is static and let me say sounds like a buzzing mosquito . The only quiet solution is with maximum brightness. The noise does not occur when holding or pressing the keys, but starts immediately after lowering the brightness and its not gonna disappear until I set the max brightness back. I havent changed,removed or checked any part so far and also ultrabay device is not causing this noise. Thinklight works fine and its neither causing nor fixing the problem Maybe just one more observation I can say, the buzzing frequency (i mean the tone) is little bit different on each brightness level. Not much but it is. Im just guessing...any capacitor/resistor damaged? I wonder what kind of electronic device could cause this sound (voltage regulator??) Maybe I could try to remove the LCD check the cabeling or whatever else to check the condition. What do you think?

To ambientscape:
Its good to hear Im not alone on this "Thinkworld" ) Did you man try to somehow fix it? Have you had a chance to check anything?

[pphilipko]

I know this may seem far fetched, but when I adjust my ceiling lamp, there's the "mosquito sound" unless you set it to max. brightness. My lamp's been doing this for three years, and it has yet to be broken. The problem with my lamp seems to correlate with your problem with the screen.

I'm sure the sound is nothing to worry about, but if you do get annoyed by the sound, then you might want to think about changing the backlight, which may be the root of the problem.

[atomba]

Yep, that makes sense. I agree with you its not much to worry about, but sometimes through the night its more comfortable to use lower brightness and that noise is a problem .
Anyway, I have a chance to try replace the backlight with one T23 not having this mosquito sound in my office.

Thanks a lot!

[dsvochak]

pphilipko's comment about his ceiling lamp reminded me that fluorescent lights will "buzz" if there's a problem with the ballast. They'll also "buzz" if there's a loose connection.

Maybe this problem is just a loose LCD connection. If we're lucky, one of the techs who frequent thinkpads.com like Len from AbsoluteRaleigh will read this thread and give us a diagnosis.

[AbsoluteRaleigh]

Did I hear my name?

I like pphilipko's thought. Backlight. Changing it is not as easy as it sounds though. If you are not extremely patient or do not enjoy working on tiny electronics just get a new LCD.

Worth mentioning, it could be the inverter, although it is highly unlikely on this model.

[Way]

My t23 had a buzzing depending on the brightness setting.Silent at maximum brightness.I had the inverter replaced under warranty and the buzzing was gone.

[beeblebrox]

What a lot of nonsense here in this thread!

The inverter has to generate up to 1200 Volt for the CCFL lamp to generate electron ionisation for emitting light.

To do this it has to "upgrade" the 10.8V from the battery or input up to the high voltage. This is done by frequency modulation and induction coils. Similar to the AC converters, just the other way round.

If you get to a certain required voltage your high frequency can be heard in the coils.

Ever wondered, why there is a humming of 50 or 60 Hz when you go close to large transformers? Now increase the frequency, you don't complain about the 15khz (horizontal beam shift, heard from the coils) of you old TV either, don't you?

Maybe a quick look into basics of physics on Wikipedia can help sometimes...

The only way to avoid the buzzing sound is to wait a few months until white LEDs start to appear in new notebooks. They need only 1.5V, not 1200V