Hi ,

Having a laptop with a suspected bad backlight or Inverter.

I had changed the BL but still no display. Can see the image on the screen
with a flashlight but the BL doesn't lit.

How can I confirm if the Inverter is OK ?

What is the voltage that I should read at the BL input ?

I have a scope if required.

Tks...

Usually 5V, but it may vary and you provide no make and model number. Good
luck.

Bob


"Ben" wrote in message ...
Hi ,

Having a laptop with a suspected bad backlight or Inverter.

I had changed the BL but still no display. Can see the image on the screen
with a flashlight but the BL doesn't lit.

How can I confirm if the Inverter is OK ?

What is the voltage that I should read at the BL input ?

I have a scope if required.

Tks...

Ben wrote:
Hi ,

Having a laptop with a suspected bad backlight or Inverter.

I had changed the BL but still no display. Can see the image on the screen
with a flashlight but the BL doesn't lit.

How can I confirm if the Inverter is OK ?

What is the voltage that I should read at the BL input ?

I have a scope if required.

Tks...


If you changed the backlight, what's left besides the inverter?
I'm gonna guess that the liklihood of an inverter failure is
MUCH greater than the liklihood of failed logic driving it.
Unless you have access to a high voltage probe, the backlight
voltage will be well in excess of the rating on most normal scope
probes. And if the new backlight is not lit, you can suspect that
the voltage ain't present. You can wave your scope probe around
over the backlight inverter transformer and tell if it's running.
There's often a cap in series with the backlight that can go open.
There's sometimes a fuse on the inverter board. Sometimes, they
go open for no reason.
mike

--
Return address is VALID!
Bunch-O-Stuff Forsale He
http://mike.liveline.de/sale.html

I have a high voltage probe. What should be the voltage ~ ?

Is a meter in AC mode (1kV) can see something or is too high ?

I also suspect that the BL taht I changed was maybe bad. Near the contact
pin on one side , I saw a very small piece of glass remove. That is why I
want to confirm the Inverter before sending the BL for replacement.

Tks for your help....


"mike" wrote in message
news:LZobi.5056$3Q4.1247@trnddc05...
Ben wrote:
Hi ,

Having a laptop with a suspected bad backlight or Inverter.

I had changed the BL but still no display. Can see the image on the
screen with a flashlight but the BL doesn't lit.

How can I confirm if the Inverter is OK ?

What is the voltage that I should read at the BL input ?

I have a scope if required.

Tks...


If you changed the backlight, what's left besides the inverter?
I'm gonna guess that the liklihood of an inverter failure is
MUCH greater than the liklihood of failed logic driving it.
Unless you have access to a high voltage probe, the backlight
voltage will be well in excess of the rating on most normal scope probes.
And if the new backlight is not lit, you can suspect that
the voltage ain't present. You can wave your scope probe around
over the backlight inverter transformer and tell if it's running.
There's often a cap in series with the backlight that can go open.
There's sometimes a fuse on the inverter board. Sometimes, they
go open for no reason.
mike

--
Return address is VALID!
Bunch-O-Stuff Forsale He
http://mike.liveline.de/sale.html

Ben wrote:
I have a high voltage probe. What should be the voltage ~ ?

Is a meter in AC mode (1kV) can see something or is too high ?

I also suspect that the BL taht I changed was maybe bad. Near the contact
pin on one side , I saw a very small piece of glass remove. That is why I
want to confirm the Inverter before sending the BL for replacement.

Tks for your help....


"mike" wrote in message
news:LZobi.5056$3Q4.1247@trnddc05...
Ben wrote:
Hi ,

Having a laptop with a suspected bad backlight or Inverter.

I had changed the BL but still no display. Can see the image on the
screen with a flashlight but the BL doesn't lit.

How can I confirm if the Inverter is OK ?

What is the voltage that I should read at the BL input ?

I have a scope if required.

Tks...


If you changed the backlight, what's left besides the inverter?
I'm gonna guess that the liklihood of an inverter failure is
MUCH greater than the liklihood of failed logic driving it.
Unless you have access to a high voltage probe, the backlight
voltage will be well in excess of the rating on most normal scope probes.
And if the new backlight is not lit, you can suspect that
the voltage ain't present. You can wave your scope probe around
over the backlight inverter transformer and tell if it's running.
There's often a cap in series with the backlight that can go open.
There's sometimes a fuse on the inverter board. Sometimes, they
go open for no reason.
mike

--
Return address is VALID!
Bunch-O-Stuff Forsale He
http://mike.liveline.de/sale.html


Short answer is that I don't know.
I expect the striking voltage is gonna be in the range of 1500V.
But that's not what you're gonna see on a meter. You're gonna need a
scope high voltage probe with enough bandwidth to see the transient.
And depending on the probe, it's gonna load the circuit. And if the
secondary is not isolated, you run the risk of blowing up the inverter
or the scope with the ground loop.
Just too many unknowns to predict.
First thing to do is see if the inverter is even running.
You can probe the primary side with the scope.
Or just wave the probe in the air near the transformer.

--
Return address is VALID!
Bunch-O-Stuff Forsale He
http://mike.liveline.de/sale.html