TC1100 high pitched squeal near cpu

[elleses2030]

I've got a TC1100 with the 1.1GHz Pentium M. After a RAM and disk upgrade a year ago, it's been operating almost 24/7 as our home (Ubuntu) server. It's been quiet, reliable, and relatively efficient.

A few weeks ago, it started emitting a very high-pitched squeal. I can barely hear it, although younger people in the house tell me it's almost unbearable when they are in the same room with it. The squeal varies depending on what the processor is doing, but it still works just fine. It had just started to need a new battery, so I first suspected the power regulators on the back of the motherboard (near the DC input).

Since no one would let me keep it running, I decided to dive in. The disassembly isn't too bad, so long as you're patient and use the right tools. Once I had it apart, it was fairly obvious that the sound is coming from beneath the CPU, not the power regulators. I thought about pulling the motherboard to look at the back side, but the photos on the HP web site show only surface mount components on the side opposite the CPU.

Does anyone have any insight into a problem like this? In the old days, I might have suspected a failing crystal or cap, but manufacturers probably haven't repaired boards for a decade or more. Have you encountered this? Any idea how long it will continue to operate? Any cure, short of a new motherboard?

A replacement board (if I can find a distributor that has one in stock) is about $500 (per the authorized HP distributor list). I can get a low-power home server for less than that. So if that's my only option, my beloved TC may have served it's last bytes.

Thanks for any help/advice.

[docg]

ebay could get you a motherboard for a lot less. You are sure it isn't the fan? It sounds like you have more of an idea than I would. My only suggestion is for sources for a used tc1100 for parts- you can pick one up under $100 at ebay if you are patient, and currently there are some tc4200 and 4400 from bargain_chain in florida that are available-- this company did well when the unit they sent first had a problem, they shipped out an exchange! This just this week and upgraded me from a 4200 to a 4400! They are out of florida and my experience was a good one.

[elleses2030]

Yep, I'm unfortunately pretty sure it's not the fan (never say never, I always say :). I could get my ear right up to the CPU, and it's a very electronic noise (at least the frequencies that I can hear).

Thanks for the tip, I'll check ebay and bargain_chain out and try some patience.

I'm still hoping someone will chime in with "oh yeah, I know what to do about that; just tweak the frazzamajazz".

[TabletRon]

Sounds like your fan to me also. It would be the cheapest place to start. Remember if you change it to use new thermal past on the top of the CPU. This is what you would look for on ebay.

[elleses2030]

Thanks for responding.

But, to quote Paul Simon "I'll repeat myself, at the risk of being crude..." I don't think it's the fan.

I can put my ear up to the fan (the fan housing is quite obvious, and the photos at HP's web site are quite helpful) and I can put my ear up to areas further from the fan. The sound isn't coming from the fan, it's coming from either the CPU, something beneath the CPU on the board, or (most likely) something half-way to the hard disk connector (some part that resonates at very high frequency).

The sound is modulated by processing operations (imagine the sound of an old CRT warbling when you display something on the screen). I'll take a WAG and say the base sound is something above 10Khz, and it's modulated (during certain types of processing) by something like a 60Hz signal. It can be instantly started and stopped by changing what the processor is doing (for example, sort a large file / stop the sort).

I find it hard to believe that the fan would change at those rates. If you think it can, please explain why you think that (or have experienced it).

I found a source of new motherboards. They were $219, but jumped to $249. I may get one anyway... I can't really find a combination of price, performance, mobility, and power consumption that's like this, even 6 years after it was new. The newer low-power systems use Atom CPUs, and they seem a bit sluggish.

[TabletRon]

I did not mean to sound like it was definitely the fan, Just that that would be the most cost effective way to go for your first try. I can't see any other place where a noise could come from in that area. Have you had it running while the case was apart? If so just for the heck of it stop the fan with your finger for a second to see if it goes away. Also I know it is not in the area but what about the hard drive? Sound can travel in the weirdest ways. The only other way I can think of trying to pin point where it is coming from would be to use a type of auto stethoscope. I hope you find the culprit and when you do please let us know.

[elleses2030]

Yes, I've had it running with the case apart. I even ran it without the hard drive (it still brings up the power-on screen), and without the connection to the digitizer. It still squeals :(.

I haven't taken the board completely out of the case, so I haven't been able to stop the fan. That's next on my agenda, since I want to see if the noise is coming from a component on the other side (not that I can do anything about surface-mount stuff).

I actually have an auto stethoscope, and I've contemplated putting an insulator on the end (it's metal) and poking around. I don't know if the extremely high frequency will make it harder or easier to use a stethoscope in this case.

The sound is pretty directional, and is loudest at the arrow shown below:

[TabletRon]

I don't know if this will help you or not but I took a picture of an old board that I have. The North bridge chip that the arrow is pointing to is just to the bottom of where the tape is. The second pic is the two I guess resistors that are directly below the North bridge chip.

[Michelle Mastin]

FWIW mine squeals too. It would sometimes seem to get better when I got the pen in range, so I assumed it had something to do with the digitizer, but maybe not. Sometimes I could just hit it a bit and it would stop (I have an SSD in mine, and it's already pretty dinged, so I'm not particularly gentle all the time). But I would agree that it most definitely sounds electrical, not mechanical. Sorry I can't help make it go away, I would just put it to sleep if it got to be too much.

[TabletRon]

If you do try it while it is apart, I know this sounds weird but try also pushing down on the heat shield above the North bridge chip. It just might have something to do with the heat and the shield vibrating or something. I know it is a far cry but just trying to think of anything it might be.