Acer Aspire 5734Z Back light problem repaired
Hi folks! Here is another simple backlight repair guide of the Acer Aspire 5734Z laptop. The customer brought to me this equipment with a problem, randomly no screen if the LCD was lift up. Hmmm I supposed there could be contact problem or have a broken cable wire.
In most of the time the LCD worked well but in some condition the backlight was gone. I opened the front cover of the LCD and searched for the inverter because from there I can follow the wirings from the motherboard to the CCFL tube. The CCFL stand for Cold Cathode Fluorescent Lamp.
After I powered on the laptop I had no luck because there was no display on the LCD. First I powered on my DSO ( Digital Storage Oscilloscope ) and put the probe over the HV transformer, I didn’t touched the transformer, just moved the scope probe in the air over the item. This is how I quickly check if the HV transformer does have some activity. If oscilloscope screen did not appear a sine wave with relative high amplitude then something is wrong.
I saw nothing on the scope. So I decide to stir the cables on the ccfl connector with a tweezers.
Be careful to work on the secondary side of the inverter board. That is the part where the CCFL got the power. On the picture above that is the side where you can see a red and white wire on right side! There could bee 1000 or more voltage !!!
Nothing happened with the moving of the wires. There was still no screen. Then I go to the left side of the inverter, where the power came from the motherboard to the inverter that is the power supply connector on the picture above.
Then I got a flickering backlight on and off situation. I pulled out the connector and inspected if there was a crack maybe or dirty or whatever. I found only a very weak connection in the socket. Maybe that could be the reason for a connection loose. I took a strong duck tape and glued it over the connector after I pulled back the connector into the socket. You can see the black tape on the left side connector on the inverter. Therefore, the connector cannot loose connection.
After a day or so testing the laptop in several mechanical conditions like powering on and off, lifting half the screen, then full, than back to half, closed, and fully opened and so on, the backlight still worked. It was already several days with the owner and he gave me a call saying the laptop was working fine.
This was another easy and cheap repair. You also need to know that there are also some hard to fix cases. I hope you enjoy my article and will be educative for someone.
This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.
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Note: You can check his previous post in the below link:
https://www.jestineyong.com/dell-1708fpt-lcd-monitor-repair/
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James
August 21, 2015 at 2:25 pm
Hi, I can Not see clearly what you did there. Just letting you know, thanks.
Chris
August 21, 2015 at 8:56 pm
I missed one picture from the post where I put a strong black duck tape on the connector which powers the inverter board.
You can watch on the picture where I explained the major components.
On the left side of the picture are the connector which comes from the mobo.
There was the problem. The connector has a bad connection. It slipped out time to time. I decide to put on a black thermal resistant duck tape, so I prevent the connector from slipping out and the back light works fine.
Sorry for that one photo what I forgot to put in my article where you could see that black tape.
Yogesh Panchal
August 21, 2015 at 3:15 pm
Congratulations! for quick fix.
Suranga Electronics
August 21, 2015 at 3:19 pm
Hi.. I like to Learn Lap Top Repair.
Robert Calk
August 21, 2015 at 3:48 pm
Good job finding the culprit, Chris. You saved the customer some money also.
Corriete
August 21, 2015 at 6:57 pm
thanks and continue to supply your findings .
Dave
August 21, 2015 at 8:41 pm
Thanks for latest CCFL problem fix.
When you get a broken plug it's really all you can do to make it work again, without any specific details.
I don't understand the logic of poking about at the HV end of the Inverter Board when there wasn't any signal picked up on the scope from the transformer.!
The lack of signal points to the LV end of the inverter.
Also I think you should have mentioned to use PLASTIC objects for the HV end and not as suggested 'tweezers' which infers metal.
Dave
Chris
August 21, 2015 at 9:35 pm
Dave you are absolutely right what the tweezers stuff mean , of course nobody should poking around with a metal object on a HV output or any other electrical output.
I use only high quality esd safe and insulated tweezers all the time.
Here is my tweezers set and from where I got it:
http://www.oficina-digital.com/catalog/product_info.php?manufacturers_id=42&products_id=1254&osCsid=kp60r65vj21167pr8q9kcst851
"I don't understand the logic of poking about at the HV end of the Inverter Board when there wasn't any signal picked up on the scope from the transformer.!"
The logic is, if the HV side have no load because of a worse contact to the light tube ( it could be a bad soldering joint, bad connector, broken wire ... ) than you have no HV output but the problem must not be in the inverter board.
In some case I got in situation does the tube was burned out and emited some small light what I didn't see on the LCD, but if I put over the HVT the scope probe I saw a nice signal from the HVT because there was a small but enough load to wake up the HVT output.
Therefore, if I see a signal on the scope but no back light then I have a bad ccfl.
If I see no signal on the scope then I start to move the wiring and see if a light come up or a signal on the scope.
If signal comes up and no light then I have a bad ccfl and a contact problem on the HV side.And this contact problem maybe killed the ccfl and will kill the new ccfl.
Try out whit your laptop. You even don't need to dissemble the monitor, just flip the probe from the scope from left to right where the inverter board is.
You are well come.
Thank you for supporting my article.
Anwar Shiekh
August 21, 2015 at 9:57 pm
I have lost count of the number of connectors that were brought back to life with a tiny amount of silicone oil, which also helps keep oxidation at bay.
Humberto
August 21, 2015 at 11:06 pm
Hi Christian, good repair and nice explanations. Keep up
aziz
August 22, 2015 at 4:18 am
Thank you very much for your help.
Gerald Millward
August 22, 2015 at 4:36 am
I don't want to be a moaning Minnie, but although the fault-finding is good, in my opinion the repair is not. In this perpetually warm enviroment, the duct tape will dry out and before long the fault will re-appear. The proper way to repair this is first to replace the inverter (very cheap on eBay) since the connector on the inverter may be the culprit. If this doesn't fix it, you should replace the (presumably) faulty LCD backlight connector. If you don't have the tools to do this, it can be achieved by replacing the connector/cable assembly by one cut from a faulty LCD panel. Make a butt soldered joint of the two cable ends and cover with heat shrink-wrapped tubing. You will then have a safe and permanent repair.
Chris
August 22, 2015 at 4:13 pm
Gerald you alright, the best repair would be to replace the connector or the inverter but at the moment I don't had one by my side to replace.
But I have a high thermal resistance duck tape. It can be used in situation for gluing together some elements where are 260C. I newer used it on so strange situation but I used it much time under the engine hood to to get together some wiring's and that tape are never got sticky because of the heat like a classic electric insulation tape.
I dont know what could be the name of that sticky tape in English but in my language we call that duck tape or so.
If somebody know the right name I would be thankful for sharing with me.
BUT! I think a better think to stick together these two parts would be as you told a heat shrink-wrapped tube.
That tube are heat resistant and will bond together stronger and stronger as the temperature rise.
You are well come and thank you for tour time and supporting my article.
musa
December 29, 2015 at 9:54 pm
thankyou
Anthony
August 26, 2015 at 6:03 am
Agree with you Gerald, it is ok to use the duct tape to prove the fault but not for permanent repair. But it is still an interesting article for education purposes that has been kindly supplied for all of us to learn from by Chris.
Ken Hart
August 22, 2015 at 6:42 am
In the USA, "Duck" tape is a brand name for duct tape, used for sealing flexible heating duct pipes. The gray or silver colored variety is electrically conductive and should not be used as an insulating tape. I found this out the hard way when I once had to do an emergency repair away from the work bench!
Terrence Yeong
August 22, 2015 at 9:52 am
Very clear description, high resolution pictures.
Even emphazised on high tension portion which is important to those new in laptop screen repair.
Rigorious testing after repair.
Full marks.
Chris
August 22, 2015 at 4:16 pm
Thanks to support my article.
No one repaired stuff can leave my bench until it is hardcore tested for minimum of 24h of working...
Biruk Aweke
August 22, 2015 at 3:47 pm
Thanks & continuto supply your findings.
Albert
August 22, 2015 at 3:54 pm
Hi Chris, good job! The Owner will be pleased. I had fixed some Backlight Inverters myself too in the past. And the connectors come in several pinsizes (4,5,6,7 and maybe even higher pincount). And some Inverter boards stop working because of the bad SMD fuses on the board power input. Mostly they are working again after bridging the fuse with the thinnest wire I could find to keep some safety against overcurrents. (because SMD Fuses with same ampèrage are mostly hard to find). The Inverters with different pincounts aren't interchangeable but all use one or more pins of the inputs as PWM controlling wires. In some cases the Board gets defect because of a bad HV Transformer or a bad contact on the Transformer itself. Or because of defect (Dual) primary Mosfets that drive the Transformer.
Albert Hoekman, Holland
August 22, 2015 at 8:28 pm
Hi Chris, thanks for sharing your repair. Maybe I have the answer on your question: "I dont know what could be the name of that sticky tape in English but in my language we call that duck tape or so.
If somebody know the right name I would be thankful for sharing with me."
I use in laptops and other heatproducing devices always Kapton Tape:
Kapton Tapes are made from Kapton polyimide film with silicone adhesive. They are compatible with a wide temperature range as low as -269°C and as high as 260°C. (www.kaptontape.com)
This tape longs for many years (>10) in laptops.
For repairing connectors in laptops as you mentioned above I use only the worldfamous WD40 fluid, dripped from a small screwdriver or small brush on the connector.
Albert van Bemmelen
August 23, 2015 at 11:10 pm
Hi dear name sharer, and fellow countryman. I always wonder why the flexible tubes/hoses that transport our natural gas (Dutch : Aardgas) to our kitchens for cooking and heating are only guaranteed for about 10 years. Because every hose has an expiring date that lasts for 10 years. But no one checks these hoses or installations. It's a wonder that nothing bad happens after this expiring date is due. And I hope these hoses aren't ever fixed by people repairing these with whatever tape or fluid they find. I even knew some people that used illegally LPG gas for cooking by using a LPG gas tank with inverted ins en outs in their Garage. (Very dangerous !!)
Just something I wondered about in our Country were everything is regulated by rules and politics.
Chris
August 24, 2015 at 4:01 am
Thank you Albert for helping to identify the tape, I think this is my tape what I use on this link:
http://www.kaptontape.com/5_Mil_Kapton_Tapes.php
I use this tape lot of time under the hood of car engine and other place where are hot comes on...
K S Goh
August 24, 2015 at 10:59 am
CCFL and associated inverter are potential electrical hazards.
A safer alternative is to retrofit with LED backlighting (e.g. http://www.aliexpress.com/item/Free-shipping-290mm-Adjustable-brightness-led-backlight-strip-kit-Update-your-14inch-laptop-ccfl-lcd-to/2055621187.html).
The toughest part of this retrofit is removing the CCFL (you may have to take apart the LCD panel just to access the CCFL) and locating the 12V supply points on the motherboard.
I have no vested interested in the product nor the company.
Brad
August 26, 2015 at 5:13 am
Just tried the link and got page not found.
Dave
August 29, 2015 at 5:13 pm
I think you included the last ")"
It works without it..
Dave
Chris
August 27, 2015 at 6:42 pm
Hmmm... very good stuff! thanks for sharing.
Ganthan
August 24, 2015 at 2:25 pm
It's really a useful tip. keep it up
Brad
August 26, 2015 at 5:09 am
I like the quick tape fix. I have an alternative solution. I have similar connectors on a CCTV system I maintain and when they start slipping I use 2 mini zip ties around connector ends and zip tie them together.
Chris
August 27, 2015 at 6:43 pm
Good solution, in my case I had no place for zip tie. 🙁
Sami Shomali
August 29, 2015 at 2:51 pm
Hi ,, I like to fix Laptop