Compaq V6500 Laptop Repaired By A Bright Idea
A customer bought in a Compaq Presario V6500 Laptop for repair. After switching on the computer, nothing could be seen on the screen. I shone my bright LED light onto the screen and could make out a faint picture of the windows start up screen.
From my research the problem appeared to be either the inverter or the backlight to be the most likely culprit.
According to some more research, a CCFL inverter is an electrical inverter that supplies alternating current power to a cold cathode fluorescent lamp (CCFL). CCFL’s are an older technology and for the moment are the most widely used backlights in laptops LCDs, but LED backlights are becoming more common. They consist of a fluorescent tube connected to a voltage inverter board which provides power to the backlight. Sometimes the backlight contains 2 tubes along with 2 pairs of inverters. The next generation’s inverter technology for the CCFL Lighting is the current resonance type inverter circuit. The resonance current which causes at the secondary side of the transformer is directly switching the primary side of the transformer through the switching transistor. It simplifies the circuit and improves efficiency.
THE DIAGNOSTIC PROCESS
The customer wasn’t in a rush to get the laptop back as it was mainly used by their daughter to play games. This gave me an opportunity to do some experiments and test different methods.
I was able to purchase a cheap generic inverter from Ebay http://www.ebay.com.au/itm/12-24V-CCFL-Inverter-Tester-LCD-TV-Laptop-Screen-6-32inch-Backlight-Lamp-Test-/400894850329?pt=LH_DefaultDomain_15&hash=item5d5731f519 for about $7 Australian with free postage.
I connected the Ebay inverter and still nothing appeared on the screen.
How could I be sure that the CCFL had blown and I didn’t have a faulty generic inverter? I didn’t want to buy another one to find that I had a different fault.
SAFETY WARNINGS!
Please be aware! Inverters may put out up to 1.5Kv AC on start-up and 500 – 700 Volts during running, which I discovered the hard way. Now I also have a multimeter to repair as well…………Ah well, just another repair, another article to write! Please be careful when dealing with an inverter. I was able to also check the frequency input with my oscilloscope. So I knew the laptop was providing the correct voltage and frequency.
By putting my multimeter on the frequency range and keeping the leads close together, but not touching, even on the outside of the laptop, a frequency reading could be obtained and the inverter can be tested for operation. This method also worked. You may check out the link below for more information:
http://www.fonerbooks.com/test.htm
I searched the net for some direction. I found a bright idea – by cutting a compact energy saving house fluro light in two, I could separate the globe section from the inverter.
After cleaning up the wires, these could be connected to the inverter of the laptop, and hey presto! – it worked. This showed that the laptop inverter was fine and only the CCFL backlight had blown.
It was quite a task to remove the screen. Screws, tape, frames and more tape held it in place.
I carefully remove the tape as I believe it is used to stop bleed out of the lighting from the sides. As I pulled it down, I could see that the end of the fluro tube had broken off, possibly from the laptop being dropped.
After changing the new CCFL and reassembling all the tape, screws and frame, I was able to start up the laptop and the screen shone with the correct brightness. The customer also mentioned that they had some virus issues, so I attended to these. So when I asked for their password, they told me –password. Will people never learn?!
This article was prepared for you by Mark Rabone from Australia.
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Anthony
May 16, 2015 at 3:24 pm
Nice work Mark and a great idea to use the energy saving globe to prove the fault ! I'm glad they are useful
for something besides just being an expensive globe. Thanks for sharing !
Anthony
May 18, 2015 at 1:24 pm
I have a question,tell me,would it be harder to repair a tablet than the laptop today?
Martin
May 18, 2015 at 4:35 pm
Much harder. Most (Not all) tablets innards are accessible via removal of the screen which tends to be bonded to the case. There is a good chance of breaking the screen and/or the digitizer whilst attempting to access the innards of the device.
Anthony
May 18, 2015 at 5:20 pm
I'm a different Anthony from the one below....To avoid any confusion.
Allan
May 16, 2015 at 4:00 pm
Thanks so much Mark for sharing. This is a real bright idea. I always say I will never stop learning. Keep it up Mark!!!
Albert Hoekman
May 16, 2015 at 4:56 pm
Good job Mark. And a very clear explanation.
Chris
May 16, 2015 at 5:13 pm
Nice job Mark.
dicksy
May 16, 2015 at 5:51 pm
nice work mark
thank you
mahmoud_tajpour
May 16, 2015 at 6:03 pm
thanks a lot mark this article was very useful for me.
thomas shelton
May 16, 2015 at 6:52 pm
Excellent job Mark. Really bright...
Paris Azis
May 16, 2015 at 7:46 pm
Hi Mark,
Brilliant idea indeed! I enjoyed it.
Regards
Bernie Scott
May 16, 2015 at 8:57 pm
That is a cool idea.....I would have never thought of that...excellent....
Waleed rishmawi
May 16, 2015 at 10:52 pm
That is why it is a good idea to have backlight testers. It save you time and effort. Thanks for sharing
Robert Calk
May 17, 2015 at 8:04 pm
That's true, Waleed: My tester works great. I also kept a good backlight from a bad display of a laptop that got junked.
But the idea Mark found can be very handy in a pinch.
Humberto
May 19, 2015 at 1:14 am
Do you know any website where anyone can buy a CCFL/LED tester for laptops?
Robert Calk
May 19, 2015 at 2:13 pm
I bought mine on ebay.
Mark
May 20, 2015 at 5:24 am
Hey Humberto,
I listed the link in the article, but here it is again.
http://www.ebay.com.au/itm/12-24V-CCFL-Inverter-Tester-LCD-TV-Laptop-Screen-6-32inch-Backlight-Lamp-Test-/400894850329?pt=LH_DefaultDomain_15&hash=item5d5731f519
Danel
May 16, 2015 at 11:12 pm
Never tought to use an energy saving bulb!! I always keep a display lamp for testing purposes... Thanks mate!
Merlin Marquardt
May 17, 2015 at 1:55 am
Very nice.
Andre Gopee
May 17, 2015 at 2:19 am
Hey Mark, Thanks for the Bright Idea. I will try that some time. Keep up the good work.
Robert Calk
May 17, 2015 at 7:00 am
Nice job Mark. It would be nice to see a photo of the laptop working though.
Edward
May 17, 2015 at 10:59 am
Thanks Mark, excellent job; every brand of laptop screen assembly seems to be very tricky,so thanks again for the tutorial. Edward from Trinidad.
Yogesh Panchal
May 17, 2015 at 3:08 pm
Excellent experiment!! good keep sharing your ideas.
Ifeatu Ikedi
May 17, 2015 at 4:47 pm
Nice tutorials. I will go and get my dumped laptop with similar issues fixed, because this tutorial seems to be a guide. Thanks once again Mark!
Lee
May 17, 2015 at 5:49 pm
Thanks Mark, very nice!
Where did you source the new lamps?
Mark
May 17, 2015 at 8:58 pm
Hey Lee,
Mainly Ebay. Here is an example - fairly priced.
http://www.ebay.com.au/itm/15-4-LCD-CCFL-Backlight-Lamp-Compaq-Presario-V6200-V6300-V6400-V6500-V6600-V6700-/220886918016?pt=LH_DefaultDomain_0&hash=item336de2e380
Gopal Sharma
May 18, 2015 at 2:57 pm
Thanks Mr. Mark Rabone for sharing your expert tips. I have a query, how inverter knows to generates 1.5kv starting and 700v running voltage. Is there any starting and running sensor. I know about the feedback for brightness control but not about starting and running sensor.
Humberto
May 19, 2015 at 1:23 am
Another laptop saved from the dump. Congratulations.
reza
May 21, 2015 at 2:28 pm
hi dear Mark Rabone
thank u for sharing this article.
m.reza from iran
Albert
May 21, 2015 at 3:46 pm
Hi Mark,
Better use a little Neon light on some kind of isolator to test if there's High Voltage in TV's and stuff. The Neon Gas will spontaneous light up from 80 Volts up. The input Impedance (10MOhm) of your Digital Multimeter likely isn't made for 1000 Volts or more. Or just use another small TL (8 Watt) to proof if the inverter works. And sometimes it's just the small soldered fuse on the inverter board that needs repairing. (In our Computer Service repair we have managed to get the Backlight inverter working again this way several times without finding any cause for it's fuse blowing up. If I'm remembering it correctly they were 1 or 2 A types).
And the cases in which the inverter needed real repairing it was mostly the (Dual) mosfets or even the HV transformer on the inverter board itself. But sometimes there was also a little fuse on the laptop mainboard just in front of the LCD flatcable (3.3 Volt) connector. Fixing that fuse mostly fixed a not working LCD screen.
Thanks for the Bright Energy Saving Light Bulb idea, Mark! (Personally I think because of the envirement issues they never should have made them as badly vulnerable they are. Knowing how quickly they end in the wastebins nowadays. An old trusted lightbulb had much more lifetime and was much cheaper too).
Albert.
sahid
May 27, 2015 at 11:34 pm
well done
Bulent
June 30, 2015 at 12:01 am
Great job, I thinking.
What is pass, password! 😀
Edouard Saint-clair
July 3, 2015 at 8:46 pm
Works every time!!!
Lamb
August 17, 2015 at 1:08 am
Really a bright idea. Now I've also mine from you.
Thank you for sharing your bright idea.
Mendall
February 13, 2016 at 8:53 pm
Thank you for sharing you information unreserved. We are grateful for all the emails send to us. It is valuable contributions to the repairing service persons everywhere. Thanks.