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Old 06-30-2018, 10:46 PM   #1
tibimakai
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Default Asus Q502L does not boot up properly

I have picked up this laptop, without hard drive and only with the motherboard soldered memory.
It starts up, LED is on and fan spins slow/fast/slow/fast a couple of times, that settles, on the fast spin. Nothing shows on the screen, not even backlight. I have tried with external monitor, still nothing.
I have to admit a mistake that I have made, but did not change a thing.
While it was on, I have pulled the display plug and blew up a capacitor, that goes to the battery(16.3V).
If I plug in the charger, the battery LED is on.
I don't have experience, with laptop repairs. I have repair equipment.
I would appreciate any help, that I could get.

Asus Q502LA-BBI5T12

Last edited by tibimakai; 06-30-2018 at 11:00 PM..
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Old 07-01-2018, 04:18 AM   #2
SMDFlea
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Default Re: Asus Q502L does not boot up properly

I think on this model the soldered memory is VRAM. Install some memory and see, and replace the blown cap. There`s no motherboard schematic available, but there is a boardview file, i can`t find a free one anywhere. https://************/threads/asus-q502la.20646/ .EDIT: if you need the boardview ask on this forum if anyone has it .

Last edited by SMDFlea; 07-01-2018 at 04:27 AM..
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Old 07-01-2018, 05:02 PM   #3
tibimakai
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Default Re: Asus Q502L does not boot up properly

OK, I have soldered in another capacitor. No change.
There are two pins at the display connector, that it seems like a previous person "played" with it, because they are not nice and straight. To me, it seems like they should still make contact, though.
I have removed a FET above it, because it seemed like it is shorted, but after I have removed it, it wasn't.
I'm kind of confused about these FETs, how they should show with the meter.
There are two at the bottom, that at least one shows like it is shorted.
Definitely, the 1.8V coil gets pretty warm. With Ohm meter, shows 27 Ohms, which is not good.
CPU is cold.
I have also installed a memory card, but did not change anything.
Attached Images
File Type: jpg 20180701_153006.jpg (975.1 KB, 84 views)
File Type: jpg 20180701_153014.jpg (995.1 KB, 72 views)
File Type: jpg 20180701_153030.jpg (945.0 KB, 58 views)
File Type: jpg 20180701_153116.jpg (1.04 MB, 68 views)
File Type: jpg 20180701_153138.jpg (1.06 MB, 63 views)

Last edited by tibimakai; 07-01-2018 at 05:03 PM..
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Old 07-01-2018, 09:28 PM   #4
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Default Re: Asus Q502L does not boot up properly

The part that blew by the display connector was a ferrite bead. Not a capacitor.

That 1.8V rail is CPU core power (which can range anywhere from 1.5V to 1.84V for that CPU). It's supposed to have a low resistance. That goes along with low voltage and high current. Reading double digits for resistance is not alarming.

The other places labeled as a short to ground are really just... ground. Those pairs of FETs are buck converters. They have a supply voltage on one side of the pair, ground on the other, and the output voltage in the middle.
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Old 07-01-2018, 11:00 PM   #5
tibimakai
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Default Re: Asus Q502L does not boot up properly

So, if the "capacitor" is gray, than it is ferrite bead?
What are these boardviews? I have never heard about them before.
If the 1.8V is there, why the cpu is not getting warm?
What should I look for?
Thanks kotnatan, but I don't know what to do there. I have past the test and I'm stuck there.
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Old 07-02-2018, 02:25 PM   #6
tibimakai
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Default Re: Asus Q502L does not boot up properly

I have forgot to mention, that if I plug in the power adapter, it constantly reboots, I can't stop this process. On battery, the fan just keeps spinning, at high RPM and can be stopped, with a long press of the power button.
Why initially, the fan RPM keeps changing, before it settles on high constant RPM?
It could be, a bad BIOS chip as well?

Last edited by tibimakai; 07-02-2018 at 03:17 PM..
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Old 07-02-2018, 03:18 PM   #7
kokono
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Default Re: Asus Q502L does not boot up properly

At this time, i have exactly this problem in Asus X555LD

"It starts up, LED is on and fan spins slow/fast/slow/fast a couple of times, that settles, on the fast spin. Nothing shows on the screen, not even backlight. I have tried with external monitor, still nothing."

"that if I plug in the power adapter, it constantly reboots, I can't stop this process. On battery, the fan just keeps spinning, at high RPM and can be stopped, with a long press of the power button."

any person have idea ?
my cpu and chip graphic ist warm
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Old 07-02-2018, 08:51 PM   #8
tibimakai
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Default Re: Asus Q502L does not boot up properly

I have just read your thread today and I thought the same thing, that sounds the same issue.
I'm new to laptop repair.
I'm wondering, can't be a corrupt BIOS chip?
It seems, like I have the right voltages as well.
Do you know the history of yours? What happened to it?
I have purchased it like this, so I don't know.

Last edited by tibimakai; 07-02-2018 at 08:55 PM..
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Old 07-03-2018, 12:07 AM   #9
kokono
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Default Re: Asus Q502L does not boot up properly

your motherboard have onboard RAM ?
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Old 07-03-2018, 08:46 AM   #10
tibimakai
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Default Re: Asus Q502L does not boot up properly

Yes, and the seller has mentioned, that bad RAM may be the case.
Can we cut the trace, that powers it?
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Old 07-03-2018, 09:29 AM   #11
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Default Re: Asus Q502L does not boot up properly

Quote:
Originally Posted by tibimakai View Post
Yes, and the seller has mentioned, that bad RAM may be the case.
Can we cut the trace, that powers it?
No. Your motherboard is different to @kokono .In his case the memory MAY be bad,there are some guides on how how to disable his RAM which involves moving caps and resistors to different places., if you do a google search "x555l disable ram" theres some guides on youtube,various forums, and bios/schematic sellers such as vinafix also sell guides. @BlueMidnight is giving you advice, it would help though if you had the schematic, if you can`t get one for free buy one,they don`t cost much.

Last edited by SMDFlea; 07-03-2018 at 09:30 AM..
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Old 07-03-2018, 12:01 PM   #12
tibimakai
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Default Re: Asus Q502L does not boot up properly

I don't have a problem buying the schematic, but from where?
On the Russian site, I'm lost.
I will find a ferrite bead and I will replace that capacitor, but I don't have any other lead, that I can follow.

Last edited by tibimakai; 07-03-2018 at 12:04 PM..
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Old 07-05-2018, 10:23 AM   #13
tibimakai
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Default Re: Asus Q502L does not boot up properly

Anybody has a BIOS dump?
I'm trying one, posted on this forum, but it makes the laptop even worse.
Power LEDs, just keeps blinking under AC adapter.
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Old 07-05-2018, 10:36 AM   #14
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Default Re: Asus Q502L does not boot up properly

Upload your original bios if you saved a backup .
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Old 07-05-2018, 10:43 AM   #15
tibimakai
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Default Re: Asus Q502L does not boot up properly

I will when I get home.
I'm new to flashing. I have a TL866A programmer.
When I did a Verify, I had a bunch of red FFFFFs. I don't remember, what was the error in red.
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Old 07-05-2018, 08:06 PM   #16
tibimakai
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Default Re: Asus Q502L does not boot up properly

I hope, that is OK how I did it.
I have re-flashed the original chip, with this file, without any errors.
Later I will solder it back, to see what happens.
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File Type: rar Asus Q502LA Rev 2.0.rar (4.2 KB, 46 views)
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Old 07-05-2018, 09:41 PM   #17
tibimakai
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Default Re: Asus Q502L does not boot up properly

I'm looking at the original dump and to me, it seems like it is empty. I did something wrong, when I have read it?
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Old 07-06-2018, 01:40 AM   #18
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Default Re: Asus Q502L does not boot up properly

In asus system there is 2 models i will need the sn to find the right one but still i will upload the 2 files
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File Type: zip Q502LAF1206.zip (3.27 MB, 49 views)
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Old 07-06-2018, 08:35 AM   #19
tibimakai
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Default Re: Asus Q502L does not boot up properly

I'm at work right now, so I don't have that. I will check that when I get home.
The model number is this: Asus Q502LA-BBI5T12. 4th gen i5 CPU.
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Old 07-06-2018, 08:40 AM   #20
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Default Re: Asus Q502L does not boot up properly

Quote:
Originally Posted by tibimakai View Post
I'm looking at the original dump and to me, it seems like it is empty. I did something wrong, when I have read it?
Are you using a clip to read the bios,or have you desoldered it. Is your tl866 software up to date, and what part number is the bios .
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