Date: 22 Oct 00 19:16:10 EDT
From: Tom Manson <[EMAIL PROTECTED]>
Subject: Re: Blank Screen
Hi folks,
Those of you who are interested, I have some minor news to report and some
questions (for those of more experience with the Libretto than myself).
To recap and provide some background for the following, my Libretto (50ct) has
had a screen failure such that the screen flashes at me when it is first
turned on, and does not show any signs of displaying anything until the next
time it is turned on. I can put the Lib on the docking station and plug a
monitor into it and the monitor works fine, so it is the LCD-related circuitry
that is at fault. Now here's what's cookin' lately:
I disassembled the screen enclosure (some of you probably saw the graphics I
uploaded to the list), and measured the voltage of the "backlight" power
supply." [I put that in quotes, because what I found doesn't realy indicate a
backlight as much as it does an electro-luminescence circuit or charge-related
device.]
Some one told me to expect 50 - 150 volts (I didn't recall if they specified
ac or dc), so not knowing the expected polarity, I set the meter I had for
600vdc. At first the meter dipped below 0 regardless of the way I applied the
probes, thus indicating an ac voltage (no wonder the wires were colored white
and blue instead of red and black). So I switch the meter to 600vac and got a
more accurate reading, at least it showed the true significance of the
circuit. It pegged the meter! I would assume that the actualy output voltage
fo that circuit is around 1000vac! I can't measure anything above 600v without
rigging up some kind of a voltage divider circuit.
So, unless the output is supposed to be dc and I have a failed rectifier or
two, that power output looks good to me.
The next step in the process then is determining what is actually bad and in
need of replacement. It appears to me that the little circuit card identified
as "FL INBERTER" [sic] on the left edge of the screen (I don't have the part
number handy, but it is on the drawing and parts list that I got somewhere
online - and from whence came the name I quoted above) is the faulty part
since it appears to house both the "backlight" and other signal decoding
electronics.
The next question (assuming that is the faulty part), is where can I get one
of these little guys and how much will it cost. I guess another question I
would ask is is it somehow matched to the LCD screen such that the screen
needs to be replaced along with the circuit card. I can't believe that the
latter is true, but there might be some trimming required once the two are
mated.
If it isn't the little FL INBERTER, (in other words if the fault is in some
other LCD circuitry located out of range of what I could see) I'm not going to
know that. If you guys happen to now if and where other LCD circuitry is
housed, please let me know.
Any assistance along these lines would be apprecited, whether it be opinion
or knowledge.
Thanks,
Tom
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