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Jim Yanik

wrote in
:

On Thu, 25 Aug 2011 08:14:54 +0100, "N_Cook"
wrote:

wrote in message
. ..
On Wed, 24 Aug 2011 08:26:30 +0100, "N_Cook"
wrote:

wrote in message
.. .
On Mon, 22 Aug 2011 14:19:37 -0700 (PDT), benitos
wrote:

On 22 août, 15:28, wrote:
On Mon, 22 Aug 2011 08:37:16 -0700 (PDT), benitos

wrote:
Hi ,

Have a Toshiba Satellite laptop with a "no display" symptom.

After checking it, i can notice a very dim picture , the CCFL
doesn't
lit.

After opening it , I found that the inverter had a fuse open
.

Replace the fuse but after , the computer did not power up.

There was a short on the inverter boards so I replaced it
with the same model.

Now , the computer boots up , CCFL lit for a few seconds but
shuts down after.

Is is possible the the CCFL is bad also ?

Thanks for your help...

It's possible. When the image first appears, is there a
pinkish hue? Also, inspect the wires from the inverter to the
CCFL carefully.

PlainBill- Masquer le texte des messages précédents -

- Afficher le texte des messages précédents -

Model is P200-MB1

Only half of the CCFL lit (kind of pink) and shuts down.
That indicates the tube is old, and dying. It gets a pinkish
tint and the current rises. Replace the tube and you will have a
good display.

PlainBill

Does one inverter supply two tubes? And if disconnecting the
problematic tube , as a proving exercise, do you have to mitigate
for overdrive to
the
single tube, even for say 5 seconds of proving use?

It varies with the design. I'm more familiar with the full fledged
inverters found in monitors, but it is very common to see one
inverter system driving 4 or even more tubes. The 'system' consists
of a single controller, drivers driving 1 to 6 (or more)
transformers, and each transformer driving one, two or four tubes.
The system contains circuitry which monitors the current through and
the voltage across each tube. The largest single part of the
circuit is the transformer, and even those can be less than 12mm
(1/2") on a side.

PlainBill

I was wondering , with a shared inverter, how they avoided possibility
of one tube striking and the other one not .

Matched tubes? Good design? Shared transformer designs also have
small capacitors between the hot side of the transformer and each
CCFL.

If you google the part number of many inverter controllers you can
find extensive information on how to design an inverter.

PlainBill

I've read that that cap acts as a short(low-
Z load) until the tube fires,then the tube is lower resistance.

--
Jim Yanik
jyanik
at
localnet
dot com