Noisy laptop

Hi all.
I am brand new to this forum so please excuse me if I am dragging up an old/resolved problem
I recently decided to rescue an old Toshiba Satellite L45 laptop just to save it from going to landfill. I am actually using it to build some jukebox software. It did have Win. Vista installed. I have now installed Linux Mint (32 bit latest version) which is a great success.
I have however got one problem. The laptop produces a fairly high pitch whistle which I had put down to the inverter.
Now I am not sure. The whistle disappears for a short while if I reduce the screen brightness, then reappears. It is not there if I unplug the power supply and run on battery, even if I turn up the screen brightness to 100% When I get it to disappear for a while it will come back if I plug in an external USB drive, again only when using the mains adaptor, and not when on internal battery. It is still there if I connect an external monitor and switch off internal screen.
I just can't think it through.
Any ideas?

 

could it be a old style hard drive, reaching old age?
try removing it and running laptop bios


or a fan that is only on some of the time?
try them in bios

 

Hi and thanks for your reply.
Unfortunately none of the suggestion you made are the cause. The fan when it kicks in and out is quiet. The hard drive has recently been replaced.
Having spent a bit more time using the laptop, sometimes for a whole day at a time, I have established the following.
My previous comment about the noise being related to load is not in fact the case.
If I run on battery there is no noise
If I reconnect the adapter to recharge, no noise until battery reaches 100% charge
At 100% charge and adapter connected the noise is full time
If I disconnect the adapter when battery is 100% charged the noise stops.
I am using the adapter that was supplied with the laptop
I have checked the adapter output voltage - it is correct
I removed battery when 100% charged and measured voltages - correct

The problem seems to be related to perhaps charging regulator in the laptop but I do not know for sure. I have read a bit about coil buzz etc. Could that be relevant?

I could run on battery and continue to plug/unplug the adapter but this is not ideal as the battery does not have much of a run time when discharging. I am reluctant to spend out on a new battery on such an old laptop as I only ever use it at desk.

Thanks

 

I feel very silly.
My wife just came into the room and asked if my power adapter was supposed to make those loud whistling noises! she picked it up and then asked if it was supposed to get so hot that she could almost burn her fingers with it!
It would seem that I was looking completely in the wrong direction. Looks like I have got not one but two bad adapters. I have now ordered a new one on line.