Henrik Enslev <no@spam.nix> wrote:
> > du har prøvet at skrue op for lysstyrken på skærmen? Det kan gøres fra
> > såvel knapper på tastaturet (F1), som fra skærm kontrolpanelet.
> >
> Ja, det hjælper ikke
>
> > hjælper det ikke lyder det som om baggrundsbelysningen er gået.
>
> Trist men nok sandt
så denne post ved et tilfælde:
Display brightness mechanisms failing (#3)
We continue coverage a problem where the brightening mechanism
(fluorescent tube) fails on various Macs, particularly iBooks.
When the problem manifests, the screen suddenly becomes extremely dark,
but normal system functions continue. Users find that they are still
able to view display content if a bright light source is held near the
darkened screen.
Note that this appears to be a separate issue from the iBook display
issues caused by faulty logic boards, for which Apple offers a
replacement program. That issue was typified by distorted video or
completely non-functional displays.
The issue may be related, however, to a problem with the iBook's
inverter board that is caused by excessive pressure inside the screen
hinge -- an issue we noted with Dual USB iBooks in January 2004. The
part being replaced by Apple in that situation was the Inverter
Assembly.
Since the symptoms in this case appear strikingly similar, it seems a
similar component in newer iBooks may be causing the problem.
MacFixIt reader Brendan Taylor writes:
"I currently have a client's iBook G4 on my bench with these exact
symptoms. The backlight ceased to operate mid-session, when she adjusted
the screen angle to near its far-open position while it was sitting on
her desk. She did not feel anything creak or pop unusually, and the
hinge works smoothly and without unusual resistance. Video is still
visible on the screen if it is lit from the side or above at a sharp
angle, and the external VGA port mirrors the video correctly. I am
backing her data up in preparation for sending it to Apple -- she does
not have AppleCare, but it is still under warranty. I will update you as
this process progresses."
Richard Dupont adds:
"I lost my display completely after a few weeks of flashing problems and
temporary screen loss. Took it to a dealer (didn't have Apple Care) who
replaced the screen. Three weeks later the screen disappeared, although
I noticed the images were very faint. Using a flashlight allowed me to
see the display. I hooked the unit up to another monitor, and everything
works great with the system, just no illuminated display. If this is a
software problem, does anyone know of an update that has been created to
fix this problem? I love my G4 but can't continue to pay for new
screens."
Meanwhile, Terry Morris offers a technical explanation of what happens
when an inverter board fails:
"While I cannot confirm this condition on iBooks I can tell you I have
seen this condition a lot. I worked for 4 years in the casino industry
fixing slot machines and many use an LCD display. The CCFL (cold cathode
fluorescent) tube is powered by an inverter board.
"The inverter boards can get hot and if the wave soldering machine used
to solder them was improperly set up then a cold solder joint is formed.
These cold solder joints may function perfectly until they reach a
certain temperature, when this happens they create an open circuit due
to expansion of the solder that literally disconnects the component
leads. When allowed to cool back down the solder shrinks and the
connection is re-established.
"I use to solve the problem by re-soldering all of the component leads
on these boards. Most times the problem would never return on that
board."
Oddly -- if this is indeed a hardware issue -- many readers report that
putting the computer to sleep by closing the lid then re-opening it
results in restoration of the black light. We're not sure if this occurs
because of a pressure change in the display hinge or is
software-triggered.
MacFixIt reader Lucas Moore writes: "I am also experiencing a similar
issue. Just purchased an iBook a couple of months ago and the same
situation has happened about 3-4 times already. It has not happened in
the past couple of weeks though. No updates were applied during that
time. Sometimes if you close the iBook lid to put it to sleep, then wake
it up about 10 seconds later the display will be back to normal. I also
have experienced the display cycle through different colors (pink,
green, grey, white, etc.) and had to manually shut down the computer via
the power button to resolve that issue. That has only happened once.
Also odd if this is strictly a hardware issue is that users with other
Macs -- including t
--
Morten Reippuert Knudsen
<
http://blog.reippuert.dk>
PowerMac G5: 1.6GHz, 1.25GB RAM, 300+80GB Disk, 8xDVD+/-RW, Bluetooth
mus+tastatur, R9600Pro, iSight, eyeTV200 & LaCie Photon18Vision TFT