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Author Topic: Pep5 on Acer AO751h freezing with screen corruption  (Read 885 times)

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Offline noakeswalker

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Pep5 on Acer AO751h freezing with screen corruption
« on: June 14, 2015, 07:01:59 am »
Hi folks,
Not sure where to post this problem, hope this is ok. Sorry description below is a bit long, but I wanted to include all of the facts....

I have inherited an Acer Aspire One AO751h netbook which had W7 os, which I never really saw working properly, and I don't know if this problem existed with W7, and that info is going to be hard to get now.
I installed Peppermint 5 on it, as per Mr. Mark Greaves' tutorial.. I've had to do some mods to get any video to play via any means, also to get the card reader to work. Works just fine otherwise. This problem (below) was present before and  after I did these small mods.
(I have these mods documented if any one is interested - they were all taken from trusted sources on the web)
Problem is:-
Intermittent screen corruption (horizontal lines- like the horizontal hold has gone out!), and immediate locking-up of nearly everything.
Only keyboard function that seems to still operate in fail mode is the Fn + F6 to turn backlight off/on. Brightness up/down not working. Touchpad not working- in fact, the faint sizzling noise of what I think is the touchpad oscillator also stops during fail mode.

It can run for hours without failing, or it can fail during the black screen of bootup (feint white lines+stopping of boot).
It often fails as I 'do' something- eg, start up an application, or even hover over the battery symbol to get tooltip in one case.
Only way out of the lockup seems to be 'last resort' type power off.
I still have a live usb stick from which I installed Pep5, and running from this as a test, I managed to see it lock up in exactly the same way one time- not during bootup, but whilst in actual use.
The one BIG symptom is that, I realised rather late, that it seems to only fail like this whilst running on battery- on AC it hasn't failed in the 3 weeks I've been aware of this symptom. Battery seems to be good, in that it has plenty of capacity, and voltage barely changes when AC is connected- using cat /proc/acpi/battery/BAT1/state to read this- assumes there's nothing wrong with I2C comms in the battery of course ....? Could faulty I2C crash the graphics chip ?
On AC, this machine runs the fan on/off temps lower than when on batt. - 42/46C compared with about 55/60C on batt.
(I got these temps using cat /sys/class/thermal/thermal_zone0/temp, I don't know which chip this is actually measuring?)
However, since this fault can appear from cold at bootup, it seems unlikely something is overheating ...? Unless there are two faults...
Apart from some user timeout settings, I'm not sure what else could be different between AC and batt running.

This Acer has the Intel GMA500 graphics in it I believe, which I though Ubuntu now had a proper driver for ? I understand that this graphics chip has been the cause of a pile of 'freezing' faults for this Acer model early on- but the screen corruption and only seeming to fail in battery mode seem to be unique to my case. I had a feeling that a Bios update fixed much of this anyway, and mine has the later Bios.
Bios is v3206.
Any ideas what cause could be, or what to try next ?
I'm a novice at all of this, but am happy doing command line stuff in a term., but be patient with me !

Machine has quite good battery life, and so I don't want to be tied to using it only on AC. And it runs so much better with Peppermint
than it did with Windows 7 !

Thanks,
Dave