Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to sci.electronics.repair
Ben Ben is offline
external usenet poster
 
Posts: 2
Default Laptop LCD repair. INVERTER or BL ?

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...


  #2   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 38
Default Laptop LCD repair. INVERTER or BL ?

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...




  #3   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 634
Default Laptop LCD repair. INVERTER or BL ?

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
  #4   Report Post  
Posted to sci.electronics.repair
Ben Ben is offline
external usenet poster
 
Posts: 2
Default Laptop LCD repair. INVERTER or BL ?

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



  #5   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 634
Default Laptop LCD repair. INVERTER or BL ?

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
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
laptop lcd, inverter,backlight,mother brd, cable,slp switch all ok but bump, it goes dark davidlaska Electronics Repair 10 March 8th 07 12:49 AM
Laptop LCD problem inverter or backlight or video board ? kk Electronics Repair 13 February 11th 05 05:48 AM
Where to find INVERTER for LCD Laptop Max Electronics Repair 3 February 6th 05 11:39 PM
Laptop LCD inverter repair cmdrdata Electronics Repair 1 December 29th 04 03:12 AM
LCD inverter repair cmdrdata Electronics Repair 0 December 20th 04 03:51 PM


All times are GMT +1. The time now is 05:40 AM.

Powered by vBulletin® Copyright ©2000 - 2023, Jelsoft Enterprises Ltd.
Copyright 2004-2023 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"