Jornada 720 annoying whistling noise

I recently bought a J720. It's gorgeous and in great shape, and has only one small flaw which might not bother some but is in fact extremely annoying to me. The unit constantly makes a high-pitched whistling noise -- similar to what I believe is called "coil noise", which is heard most clearly when placing your ear directly over the speaker grate on the back. I at first assumed this was caused by the CCFL inverter circuit for the backlight. However, this does not appear to be the case, as the noise continues even when the device is OFF (i.e., in standby, although it does get a LOT quieter then and you have to actually hold it to your ear to hear it). To make it completely shut up, I have to entirely pull the battery and unplug it from power.

The noise appears to be related to system load, i.e. power consumption. For example, when not in standby and the monitor off, the noise can be observed to slightly change pitch for the duration each time the green LED on the front blinks. Also when booting JLime or NetBSD, the noise gets louder and more annoying--although mind you at this point I only have a 64mb CF card and no reader to partition it with, so I only get as far as booting the kernel and then it panics unable to mount root fs; I don't know if the noise would return to WinCE levels upon reaching the prompt.

This reminds me of a less annoying similar phonemenon I've seen on many other computers especially laptops. For example, I have a diskless Dell latitude laptop being used as a server. Every time it accesses the network, it makes very soft high pitched little blippy tones from the sound card in time with the transmit light blinking on the NIC. I don't know exactly why that is, but they seem like they might have similar causes.

Since this seems to be coming from the speaker grill, do you think it's possible the coil in the speaker could be picking up ambient EMI in the unit and replaying it as sound? In terms of likely to generate coil noise an unshielded coil with an amplifier cone in front of it seems a prime suspect? I tried muting the speaker in software, and plugging into the headphone jack. Neither had an effect. But then, in my hypothesis, the internal speaker could be directly picking up signals through electromagnetic induction.

I'm considering opening the unit and trying to remove the internal speaker entirely, which I'm seriously hoping is a seperate unit with a plug and not just wires that would have to be cut, or even worse, some surface mount thing soldered directly to the board. OTOH, I'm not sure if maybe the noise is just louder around the speaker grill because that's a hole in the case for sound to escape easier.

Has anyone else noticed this? Any suggestions? If you've ever opened one, do you know if the internal speaker would be easily removable so I don't risk breaking something if not? I totally love this unit, but for me, I'm afraid the noise will make me want to stay away from it. Mind you, this is a fairly quiet, scuttle, and pretty high-pitched sound - some people might not even notice it, or it might be too high-frequency for them to hear. So when I talk about how annoying it is, I mean how annoying it is TO ME.

Plug in an earphone jack to disable the speaker and see if the sound quits. Or if you don't have a blank jack, plug in a set of headphones and see if the noise relocates to them and not the device...

That will at least pinpoint the sound as coming from the speaker not something being induced within the circuitry. I've had capacitors squeal like that before however, but normally more powerful electrolytic ones, not like the type found in these little handhelds....

Based on your discription, I would surmise that you're hearing the processor chatter due to RF interference from a bad IC. It's very common on them.

Rich: I tried that, the system sounds redirected as you would expect, but the chatter noise did not appear in the headphones, and was still present at the speaker grille. However I'm not entirely convinced that proves it's NOT the speaker, as like I said I'm hypothesizing there may be electromagnetic induction going on.

C:Amie: Glad to hear you've heard of this! Yes, processor chatter does seem to fit. Is that fixable, and does it mean the sound is coming out of the speaker? This is primarily a hack-around-in-Linux deal I got this for, and if it would get rid of or significantly reduce the noise I would be more than willing to simply disconnect the speaker and make do with headphone-sound only.

Edited by rogueeve 2010-09-16 6:14 PM

Yeah, can you shield the ic that is causing the interferrance?

Unfortunately it's probably more replace the IC than shield it.You'd have to identify it first though. Something that isn't easy on its own.

So does everybody's Jornada do this, or just mine? I don't have a Torx 6 yet to open the unit so I'll have to wait until then to obtain further information.

Mine is absolutely silent....whew, lucky me.

Yes, one of my J720s used to make noises because of a bad screen connection.

This seems to plague some equipment as they age.

I swear, some of my machines used to hum and tap. Then it all miraculously stopped when I got divorced.



Edited by technogeist2k9 2010-09-17 9:01 PM

So, sounds like it's not totally rare, but technically, mine is "broken"? I'm trying to decide what to do if it's not an obvious fix once I get it open--if there's something that could be replaced I could consider buying another one for parts, or possibly just selling it and going with the MobilePro 900 instead. Does anyone know if the MP900 will run Linux, or is that only working on the 900c at the moment?

No, technically not broken. I've seen NIB 700 series do this and never have any other issues at all.

Sinclair/Timex ZX series were notoriously noisy, mostly just a side-effect of the cost-saving mentality at Sinclair computers. Perhaps the first example of sub-$100 machines, and way before the current 'Race to the bottom' netbook craze.

Edited by technogeist2k9 2010-09-18 12:41 PM

mine also does the same. It's not normal for you. For me it;s normal. A PC roars but a laptop even if is small and light brings also noise. So no bother for me. It's electric it's a gadget it is normal. I have to make yoga to hea it ) or to put my ear on the back of the unit wich is not how i use this toy.