Burned out LCD Inverter

[samf48]

I was wondering if anyone knew what could cause an LCD inverter for a
HP Pavilion ze4805 to burn out. The screen used to work and then one
day went out. My first thought was the ccfl backlight, so I replaced
it. It worked for a few minutes when I turned the unit on then it went
out again. Now when I turn it on initially it lights up for a second
then goes out. You can see the LCD is working if you view it at an
angle. The second thing I did was replace the inverter. That worked a
little better I was able to boot to windows then all of a sudden it
went out. Now it does the same thing as before. Could there be
something causing the inverter to short out? Also would the backlight
even flicker if the inverter was damaged. Any suggestions? Thanks

 

[kony]

I was wondering if anyone knew what could cause an LCD inverter for a
HP Pavilion ze4805 to burn out. The screen used to work and then one
day went out. My first thought was the ccfl backlight, so I replaced
it. It worked for a few minutes when I turned the unit on then it went
out again. Now when I turn it on initially it lights up for a second
then goes out. You can see the LCD is working if you view it at an
angle. The second thing I did was replace the inverter. That worked a
little better I was able to boot to windows then all of a sudden it
went out. Now it does the same thing as before. Could there be
something causing the inverter to short out?

It'd short out of there was some problem with the wiring
to/fro it, i mean a degraded state now that didn't exist
originally... do you see anything like that? It shouldn't
really be hidden. Otherwise I'd suspect the power supply
before it is going bad.

Do the two inverters look identical, or is it possible the
first was a *valid* failure and the 2nd just wasn't suitable
for the lamp? Same with lamp, did it look the same?

Also would the backlight
even flicker if the inverter was damaged.

Sure, depending on the shades of grey you use to define
damage... it's possible.

Don't know what you're comfortable doing but i'd probably
hook a different power supply up to (the invertor and lamp
alone) see if the two in isolation worked ok, and measure
the monitor power supply with a multimeter, make take a
closer look at it if the alternate power source runs the
inverter and lamp ok.

 

[samf48]

Thanks for the prompt response. Sorry I'm still kinda amateur when it
comes to details. When you say the power supply are you referring to
the external power supply plugged into the laptop, or is there a
component on the inverter board itself that supplies the power. At
first I thought it might be a short of some type, so I moved the wires
slightly while it was on and it made no difference. The new inverter
is slightly different looking than the older one. Here is an important
detail; I dismantled the backlight assembly and the inverter board and
set it next to the laptop (still connected, and grounded of course)
then I powered it on and let it sit for over an hour and it stayed on
just fine. When I reassembled it, it would turn on for about 2 seconds
then kick off again. The external power supply is brand new.

 

[kony]

Thanks for the prompt response. Sorry I'm still kinda amateur when it
comes to details. When you say the power supply are you referring to
the external power supply plugged into the laptop, or is there a
component on the inverter board itself that supplies the power.

yes, one of those two but I don't know which... in theory it
would be possible to use either to power the invertor board.
If you can trace back the wiring you may have some idea
where it derives power... but of course using a multimeter
to measure would do well too. However, below you seem to
indicate that the same power source is sufficient when the
inverter and lamp are external to the system so it would
seem the power supply isn't the problem.

At
first I thought it might be a short of some type, so I moved the wires
slightly while it was on and it made no difference. The new inverter
is slightly different looking than the older one. Here is an important
detail; I dismantled the backlight assembly and the inverter board and
set it next to the laptop (still connected, and grounded of course)
then I powered it on and let it sit for over an hour and it stayed on
just fine. When I reassembled it, it would turn on for about 2 seconds
then kick off again. The external power supply is brand new.

"External" just means the whole laptop supply or is this a
second supply that is only being used to test the inverter?

If it's same whole-laptop supply then i would start to
suspect a short or just a discontinuous wiring problem, a
break in the cords or bad connector contact. With power off
you could probe around for continuity with a multimeter.

 

[samf48]

yes, one of those two but I don't know which... in theory it
would be possible to use either to power the invertor board.
If you can trace back the wiring you may have some idea
where it derives power... but of course using a multimeter
to measure would do well too. However, below you seem to
indicate that the same power source is sufficient when the
inverter and lamp are external to the system so it would
seem the power supply isn't the problem.


"External" just means the whole laptop supply or is this a
second supply that is only being used to test the inverter?

If it's same whole-laptop supply then i would start to
suspect a short or just a discontinuous wiring problem, a
break in the cords or bad connector contact. With power off
you could probe around for continuity with a multimeter.

Thanks for your help. It looks like it was a short with the ends of
the CCFL and the wires connected to the inverter.