[elroc]

As the heading states we have an N8 in the office (one of about 5) which exhibits a very strange symptom.

After the first few days of having terrible battery life, even when doing very little with the phone, we tracked down the error to something which happens when keylock gets activated the first time after starting the phone.

Using Nokia Energy profiler, we've found out that as soon as keylock is activated the CPU usage goes to 100% and never comes down afterwards, except when turning phone off and on again.

Done factory resets (via phone meny, Restore and Delete data) and this problem shows up even when installing only the most basic apps - last time it appeared after installing swype, so now resetting and installing nothing.

Any ideas?

[romperompe]

Does the phone become hot?

[elroc]

Slightly warm yes, but not to a level which is a lot more than other N8's in the office. 

[psychomania]

Is the phone going to screensaver or just showing the homescreen under the dimmed backlight?

Does the phone have an active data connection, for example if you have push mail enabled or online homescreens?

[elroc]

Screensaver works fine, black screen/clock whatever. No active data connection.

Some further info - Had bubbles installed from Beta Labs, after noticing 100% usage issue after keylock removed the bubbles app (uninstalled). After no change tried a factory reset  (Reset and remove data from phone menu).

So with 'clean' phone it still does this now, but when loading TaskMan app, it seems that the 'qmlviewer' which installed with Bubbles app is still listed as installed. Could it be that the updated QT libraries are not removed when doing a 'reset and remove data' on the phone, and that this could be causing the problem?

[psychomania]

I've got bubbles installed and not noticed any warming or reduced battery life on mine though.

Do you have any other QT apps or recent beta's installed? The nokia big screen beta has been problematic in other ways so may be worth removing that if you have it.

[elroc]

We also have Bubbles installed on a few other N8's in the office here, also without problems. 

At the moment there is nothing additionally installed on the phone after a factory reset (except Nokia Energy Profiler to check cpu load), and it still gives the same problems. Really hoping it's some bizzarre software fault, and not hardware related.

Big screen was installed, but removed with the factory reset (We assume).

[psychomania]

This is definately an odd one!

Which reset method did you use? Dialling *#7370# or the four finger method?

[elroc]

Menu -> Settings -> Phone -> Phone Management -> Factory Reset -> Deleta data and restore

From what I read elsewhere it compares to *#7370# method. Been a bit scared to do the four finger method due to reports of it causing all kinds of other problems.

[psychomania]

Glad you used that, it is the same as the code. I don't recommend the four finger method as it leaves you without properly working qt or maps.

I personally at this stage would get the phone looked at by a nokia care point. They can do the hard reset without loss of qt and rule out if it's hardware or software.

[elroc]

Well to report back, it seems we found the problem, or at least fixed it.

After much fiddling and trying different things it was finally tracked down to transfer of an old video (or photo?) from the previous phone (E71).

When the phone was received initially, a full transfer was done from the previous Nokia E71. Subsequent file backups and restores were done from this N8 post transfer, so all the photo/video files wer pulled from there.

After a clean reset each bit of backup was restored seperately (Messages/notes/calendar/etc) until loading photos/videos, which would again trigger the 100% CPU load on keylock. Then removed restored videos/photos from phone manually and the CPU would drop back. When transferring the photos and video's via Ovi suite, problem doesn't occur (restoring from backup causes the problem)

So the final verdict seems to be fault was caused by a corrupt video (or photo) which maybe got corrupted in the initial transfer from the old phone. But phone is stable now, battery life is tons better, and all round better experience.

[DerScot · Accepted solution]

Some additional feedback on the SOLUTION to this issue (it's my phone that Elroc has been discussing on my behalf).

Between Elroc and myself we have managed to nail down the exact cause of the problem and it is 100% reproducible.  The issue was a corrupted jpg which was transferred to my N8 from my E71.  We have used other corrupted jpg's and another N8 in the office, and the results are the same.

To simulate, copy a corrupted jpg to the "Images" directory on the mass storage of the N8.  The moment the keylock/screensaver activates, cpu load shoots to 100% and does not come down. Power consumption of the device correspondingly increases.  The N8 seems to do some indexing tasks at this point and when it hits the corrupted file, it get's stuck. You cannot remove the file at this point. To return the phone to normal, you need to restart the phone and delete the corrupted file before the keylock kicks in.

I hope that this bit of info helps someone else to avoid hours of misery

P.S. Additional symptoms when the phone in in this overload state is that apps such as the Photo browser, Video browser and Music player appear to "hang up" on opening.

[pavlaras1]

Nokia batteries always is awfull even if there is any problem or not to the software.
I need to find 1 developer of Nokia battery team to start building higher capacity batteries up to 3.000mAh.
There is more than 10 years now that they build almost the same capacity batteries.
They must stop building only 1.200mAh or 1.300mAh batteries.
Start building 3.000mAh batteries.
We have trully problem when we charge 2 and 3 times dvdrw time our phones.
Start solving this years problem.