On Thu 27 Jun 2019 at 17:20:16 (-0400), Gene Heskett wrote: > On Thursday 27 June 2019 14:13:22 David Wright wrote: > > On Thu 27 Jun 2019 at 18:44:59 (+0300), Reco wrote: > > > On Thu, Jun 27, 2019 at 10:24:51AM -0500, David Wright wrote: > > > > That has led to finding these lines in systemd's journal: > > > > > > ... > > > > > > > Jun 27 09:47:06 west systemd-backlight[615]: [0;1;31mFailed to > > > > write system 'brightness' attribute: Input/output error[0m > > > > > > ... > > > > > > > which suggests there's something wrong with the backlight. > > > > > > Hardly. More likely there's something wrong with the appropriate > > > kernel facility. > > > > I'm afraid that's unlikely, based on the evidence that you snipped: > > > On Fri 10 May 2019 at 13:20:39 -0500, David Wright wrote: > > > > My interest in this stems from a Laptop on which you are blind > > > > until the kernel loads (ie text pours down the screen). No > > > > boot selection menu, no CMOS screens, no Grub screens. > > > > ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ > > > > When the laptop is being powered up regularly, the display works for > > about as long as the progress bar on the DELL screen takes to cross > > from side to side: I would estimate it's about one second. The problem > > came on gradually in Jan 2017. During use, the screen would flicker > > a little, then die. > > > > So my strategy was (1) set the CMOS to boot USB/optical/hard drive in > > that order. I did that a year ago, after it had been powered off for > > a week. (2) Leave a stretch installation USB stick by it, ready for > > whenever I got a chance to use it. (3) Go on holiday. When I got > > back, I had a long enough period with a display showing to get to: > > […] > > at which point I'm home and dry. > > > > > Basically what this systemd unit tries to do is to write a saved > > > value to /sys/class/backlight/intel_backlight/brightness. > > > Kernel responds to this with EIO, which is unusual for the laptop > > > (to be expected for the desktop as there's no backlight there). > > > > > > It may be possible to workaround this with certain knobs of i915 > > > kernel module (enable_dpcd_backlight or invert_brightness), I'd try > > > the latter first. > > > I.e. try adding "i915.invert_brightness=1" or > > > "i915.enable_dpcd_backlight=1" to the kernel's commandline. > > > > Yes, I've also looked at the values from /sys/…/*backlight/… and they > > all behave sensibly. But the screen flickers a little, then goes out. > > That's why I think it might be something like a capacitor charging up. > > Over a period of weeks, it could discharge back to behaving normally. > > > > But I'm not looking for a fix to the problem, just workarounds to make > > it possible to do things like install, that require the early screens > > which the external monitor won't display. > > That sounds an awful lot like the filter caps have failed. If handy with > a small screwdriver, open that lappy and check all the aluminum cans > for bulging where the scratches are across the tops. And if possible > since the psu bricks are well sealed, try a fresh psu. If the cans have > bulged tops, that's a sure sign the electrical characteristic called ESR > has gone above and ohm or so. Unless you are handy with a workstation > type soldering kit, its probably less trouble to just replace the lappy > with a new one. There was a period a decade back where the capacitors > were legendarily bad. Your unit may have some of them in it.
I thought you might pop by! I agree, but I don't think I'll be opening it up. It went through a bad patch about 8 years ago when it would just turn itself off (as if you'd held the power button) at random times, but usually when adjusting the screen angle. Then I had a failing battery (the large one), during which it was the sole PC I had access to. Later, the spare smaller battery became worn out, so now it runs permanently connected to a monitor and the mains PSU. I only run it because it's fast (2 cores at 1.2GHz) though it does run hot. AFAICT the PSU is ok as I have a spare that makes no difference. But it's not worth spending any money on. Cheers, David.
