Folks,

Sorry for posting again so soon after joining, but my newly found
Pismo is giving me problems again.

It was working more or less fine a couple of days ago.  I had Mac OS
9.2.2 running on it without issue.

Now, all of a sudden, the backlight is acting strangely.  When I boot
the machine I get the normal chime.  The display comes on (with the
backlight).  But then as soon as it boots into the OS the backlight
just stops.  Using a flashlight I can see everything is loading
properly and that the display is perfectly normal, except there's no
backlight.  I've tried fiddling with the brightness settings and it
makes no difference.

At one point I put it to sleep and when it woke, the backlight came
on.  Now the backlight won't come on at all after waking the machine
from sleep.

I tried installing OS X (10.1) on it and it, oddly, had the backlight
come on during the install.  Once it was installed it did something
odd.  The backlight didn't come on.  So I used the brightness controls
to turn it all the way off.  Then increased the brightness and the
backlight came on.

However, if I pushed the brightness settings more than halfway, the
backlight dies.  If I turn it all the way down and then back up a bit,
the backlight (albeit it not very bright) comes on.

So I tried 10.2.  The backlight worked during the install process.
But when I booted it back up, the backlight was off.  Fiddling with
the brightness controls under 10.2 did nothing.

I noticed that when using 10.1 if I turned the brightness controls all
the way down the display itself would shut off completely.  Couldn't
see anything even with a flashlight.  Then when I turned the
brightness back on the display came to life.

Doing the same thing under OS 9 and 10.2 didn't blank the display and
therefore did not turn the backlight back on.

I've checked the connections between the display, the inverter board,
and the logic board.  All of them seem tight and I see no cable
breakage.

Also, I have tried zapping the pram and resetting the PMU many, many
times.

One other thing:  If I boot the machine into system picker, the
backlight comes on and stays on.  Same thing if I boot it into Open
Firmware.  The problems seem to occur the second the OS boots up,
regardless of which OS version it is.

The machine has become unusable at this point.  I thought at first it
was a software problem but I'm not so sure now.

If anyone has any ideas, I'd be grateful.  I don't have extra parts
for this machine so swapping parts out simply isn't an option.  With
the possible exception of a (very) few Lombard parts I fished out of a
broken Lombard a few months ago.

Thank you.

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