Ed said:
I have a Sceptre X9 LCD monitor that needs to be powered on and
off about 8-10 times before it stays on. Do I just throw the whole thing
out or can I get some kinda circuit board to repair it? Thanks.
One item that causes a black screen, is a failing "inverter board".
http://www.powercome.com.tw/INVERTER/2LAMPS.JPG
http://www.powercome.com.tw/INVERTER/4LAMPS.JPG
The backlight on older monitors, is almost exclusively done by
CCFL (cold cathode fluorescent tube) and inverter board. The
inverter produces 600-1000 VAC at a low current, to cause the
tube to light up. Depending on the size of the monitor, there
may be multiple tubes and multiple inverters. Some inverter
boards, may even drive up to four tubes. On a small monitor,
perhaps a single inverter failure, results in the whole
screen going dark.
(A bundle of replacement CCFL tubes.)
http://tvparts4less.com/images/BACKLIGHT LAMPS.jpg
it doesn't take much to overload the inverter, and cause it to turn
off. The inverter may light for the first couple seconds, but
then slips back to a slightly lower voltage, and at that time,
the CCFL may go off again. So when the thing is marginal, you
get light for two seconds, and then it goes off again. The
screen is still being updated, but with no source of backlight,
you can't see anything.
New inverter boards are available. There are outfits on the
Internet, charging $70 for an inverter board. You know they
don't cost that much to make. It's as profitable a business
as selling automotive tires.
To work well, an inverter should be "matched" to the tube(s)
it powers. Generic substitutes may not be that good of a match.
Sometimes the result is, the repair doesn't last as long as
you'd like.
It is less common, for a monitor to last long enough, for
the CCFL tube to wear out. On cheap monitors, you're more likely
to blow an inverter, than have the tube wear out.
So yes, in theory, you can replace an inverter. The manufacturer
of the monitor, doesn't generally advertise replacement parts.
So you'd be dealing with the skills of people on the Internet,
offering you "equivalent" solutions.
Another test you can try, is temporarily turn down the intensity
of the screen. That may allow you to get several more weeks
from the monitor, before it starts winking off again. Turning
down the intensity, takes a small bit of loading off the
inverter, and may help keep it running.
Another problem with recent monitors, is problems with
sensing, between the monitor and video card. Sometimes
the black screen, is because the video card can't detect
the presence of the monitor and the video card turns off
its output. And that is harder to diagnose and find a
solution for. In some cases, the simplest solution to
that (on monitors with multiple input types), is to
switch to using VGA.
Paul
