Hi, I have a Thinkpad T520, i5 with integrated graphics. Some days ago I decided to try upgrading my laptops screen to a FHD one, when I first installed the new screen it all went nice and smooth and worked perfectly. Unfortunately I decided to swap back the old screen except this time I didnt take out the battery, now neither the old or new screen backlight will light up. So ive been reading the possible causes and I was hopeful it was something simple like a blown fuse, because the computer works perfectly on external monitors and I can even do normal stuff if I point a flashlight at it, that means the only problem is theres no backlight, the led board (where the wifi and bluetooth leds are) works ok too.
I couldnt find the specific diagram for the T520, but I found the one of the W520, these machines are very similar and its my understanding all screen options are compatible between them, so I believe at least regarding the lcd circuitry they are the same, both are led backlight btw.
Attached to my post is the pdf schematic , on page 30 there is the motherboard 40 pin lcd connector and its components. What I understand is the fuse F6 carries a 3vcc power and is the one in charge of switching backlight on or off, F2 is for the lcd itself and the one marked as F1 carries the main 20vcc power for the backlight led. After testing continuity with a multimeter F1 is open, and it also seems to have a slightly different voltage when tested between its sides and sides with motherboard ground, also I may be doing something wrong because I cant read its ohms, it just marks 1 on all scales. F6 and F2 have continuity and zero volts across them. That means F1 is bad right? I read voltage should be zero across them.
Now, Ive been looking for someone that sells smd components and fuses, and failed because I cant find someone who provides these without importing and consequently waiting up to a month and I have no credit card anyway, I havent had luck with local repairshops either because they want to charge me what a new computer would cost and the so called motherboard component level repairshops would just put a solder blob over it, something that may work but in that case why pay if I can do that too
My questions are: am I correct in assuming its simply the fuse whats wrong? Do you guys think I should test further to for example see if the 20V are actually provided right before the fuse? Or maybe check the whole lvds cable and make sure it has continuity and no shorts. Im a little afraid of breaking something else if I have to do tests with power on and battery. And, considering I cant find an exact smd replacement, can I use instead one of those little car fuses? I'd solder two little wires to it and then solder it on top of the old fuse, I can find them with the same specification of 3A 32V, is this a good idea? Are glass fuses acceptable too? And does anyone know if those are fast or slow acting and if that matters? I know this sounds like a really cheap and dirty fix, but money's short and thats better than simply bridging. Unless I can trick Lenovo into fixing it for free because the computer still has almost 2 years left of warranty.
I also attached the screen im upgrading to product spec. pdf sheet and a pic of the backside of the connector, there's nothing of help on top. Thanks in advance.
I couldnt find the specific diagram for the T520, but I found the one of the W520, these machines are very similar and its my understanding all screen options are compatible between them, so I believe at least regarding the lcd circuitry they are the same, both are led backlight btw.
Attached to my post is the pdf schematic , on page 30 there is the motherboard 40 pin lcd connector and its components. What I understand is the fuse F6 carries a 3vcc power and is the one in charge of switching backlight on or off, F2 is for the lcd itself and the one marked as F1 carries the main 20vcc power for the backlight led. After testing continuity with a multimeter F1 is open, and it also seems to have a slightly different voltage when tested between its sides and sides with motherboard ground, also I may be doing something wrong because I cant read its ohms, it just marks 1 on all scales. F6 and F2 have continuity and zero volts across them. That means F1 is bad right? I read voltage should be zero across them.
Now, Ive been looking for someone that sells smd components and fuses, and failed because I cant find someone who provides these without importing and consequently waiting up to a month and I have no credit card anyway, I havent had luck with local repairshops either because they want to charge me what a new computer would cost and the so called motherboard component level repairshops would just put a solder blob over it, something that may work but in that case why pay if I can do that too
My questions are: am I correct in assuming its simply the fuse whats wrong? Do you guys think I should test further to for example see if the 20V are actually provided right before the fuse? Or maybe check the whole lvds cable and make sure it has continuity and no shorts. Im a little afraid of breaking something else if I have to do tests with power on and battery. And, considering I cant find an exact smd replacement, can I use instead one of those little car fuses? I'd solder two little wires to it and then solder it on top of the old fuse, I can find them with the same specification of 3A 32V, is this a good idea? Are glass fuses acceptable too? And does anyone know if those are fast or slow acting and if that matters? I know this sounds like a really cheap and dirty fix, but money's short and thats better than simply bridging. Unless I can trick Lenovo into fixing it for free because the computer still has almost 2 years left of warranty.
I also attached the screen im upgrading to product spec. pdf sheet and a pic of the backside of the connector, there's nothing of help on top. Thanks in advance.
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