sdlomi2 said:
I've got a Norcent 17-inch lcd monitor. It's been working well for over
a year(on Win XP Pro) since I bought it new. Now, when booting, it shows
none of the black-and-white stuff(iirc), but shows a pic of desktop just for
a moment and then all goes black again. Does the same on 2 other computers.
My computer works well on a new ViewSonic lcd and also on 2 crt's I have. I
have made no changes, soft- or hardware, other than I did uninstall it &
let XP Pro re-install it.
Does anyone have an idea what's wrong and a guestimate of cost of
repair? Do you need more information?
Thank you for any and all ideas. s
The "weak link" in LCD monitors, are two components in the back.
They are the CCFL (cold cathode fluorescent lamp) and the inverter.
The inverter converts a low voltage, like +12VDC, to around 1000 VAC.
The lamp uses around 3 milliamps, for a total power draw of 3 watts
per lamp. If the lamp decides to draw more than its characteristic
current, the output voltage of the inverter drops, and perhaps if it
drops to 700 VAC, the lamp may cease to glow (extinction voltage).
The larger the monitor, the more lamps are used. There could be
from 1 to maybe 6 lamps. Sometimes one inverter drives two lamps.
It all depends on the size of the monitor, as to how many you will
find.
Inverters and connectors are failure-prone. Based on reports in the
news groups, inverter problems far outnumber CCFL failures. A CCFL
should be good for 20,000 hours or more. But some of the inverters
seem to be packing it in, well before that period of time. A CCFL
failure might show as a discoloration, or a gradual loss of intensity,
whereas other problem types go from working one day, to dead the next.
Since the inverter output is a high voltage, sometimes the problem
can be dust causing the HV to arc over. Or, the connectors may begin
to make poor contact, in which case disconnecting the connector, and
reconnecting it, may restore operation for a short period of time.
(Note - if you find any foil around the assemblies, be careful to
put it back the way you found it - the foil may be part of the
circuit, or affect how much voltage is needed to make the CCFL work.)
Another hack you can do, is turn down the intensity of the screen.
When you do that, less average current is pushed through the CCFL,
and sometimes that reduction in current, allows the inverter to
keep running when otherwise it would switch off.
The hardest part of the repair, will be finding good replacement parts.
There are web retailers who sell inverters and CCFL lamps, but it is
pretty hard to determine if their "substitute" parts are really
the correct ones or not. Since the inverter and the CCFL work as
a pair, sometimes mixing and matching original CCFL with substitute
inverter, yields a marginal repair. So your best hope, is that when
you disassemble the back of the panel, physical handling of the parts
will be enough to get it going again.
It would be so nice, if you could buy exact replacement parts from the
manufacturer, but I doubt that is going to happen any time soon.
And in terms of finding someone to repair an LCD monitor, I don't know
who I would trust to do the work. If I thought a certain service
organization, had access to exact replacement parts, then they may
be the people to do the work. If it is just some guy on the web, there
is no way of knowing how long the repair will last.
I'm currently using an LCD, and I'm not looking forward to the day when
the inverter goes on it. I don't expect the life of my LCD to be anywhere
near as long as the CRT I used to use. Maybe when the ones with LED
backlighting become more popular, tales of broken inverters will be
a thing of the past.
Paul
