Toshiba L55-B5276 turns on, but screen is dead

[tibimakai]

A coworker gave me his laptop to look at it, if I can fix it.
Power button, power LED and charging LED turns on. Fan spins up an off(as it should), CPU warm, all the voltages are there, 1.08V, 1.7V, 1.35V, 3.3V, 5V and 19V(at LCD).
External monitor not showing anything(tried VGA and HDMI).
There is not even backlight on.
There is no BIOS battery on this board(a first for me), to reset.
I ran out of ideas? It could be a bad BIOS?
Coworker said that when he turned it off, it was working. After 1 1/2 years he turned it on, and nothing happened. Course the battery was drained. I have charged it and now it turns on and does, what I have mentioned earlier.
I'm a newby, don't be to hard on me. I don't repair laptops as a hobby.
Any help would be appreciated.

[piernov]

Re: Toshiba L55-B5276 turns on, but screen is dead

Try without the main battery pack.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have done that, no change.

[mcplslg123]

Re: Toshiba L55-B5276 turns on, but screen is dead

MB code?? Is it discrete graphics model??

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

DA0BLIMB6F0 REV: F
No graphics GPU, just the i5 CPU.
I have tried with a CD-R flashing the BIOS, but nothing has happened. Started reading and then just stopped.
If I swap the two memories between them, the laptop enters in a reboot loop.

[SMDFlea]

Re: Toshiba L55-B5276 turns on, but screen is dead

Schematic for reference,post #7 https://www.badcaps.net/forum/showthread.php?t=66866

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

That seems like, it is for other models, no?

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have ended up replacing the mobo and the laptop is working great, returned to the owner.
I'm left with the mobo and I don't feel like giving up, just yet.
I have got a new BIOS IC and I have reflashed it, with the dumps that circulates on this forum Version 2.0. No change, still starts, power LED turns on, fan turns on, CPU starts warming up(gets pretty warm, by the way). Consumes around 250-300mA.
This obo, does not have a Bios battery and, I can't find a Bios reset point either.
At the moment, I only have the fan/heatsink and the power button board. I don't even have a proper memory either. It is an i5-4210 CPU.
I'm a beginner, so please take it easy with me.
I'm looking at the mobo, with a thermal camera and I don't really see any hot spots, other then the CPU and the 1.7V Mosfet.
At each coil, there is a voltage, 1.05V, 1.35V, 1.7V, 3.3V, 5V. 19V rail is there. On coil has power at the startup, but very fast starts to drop. I'm guessing, it's that the battery charging power source and since I don't have a battery, it stops charging.
Any input would be appreciated.
The owner said, that one day it was working and the next, it would not turn on. No image, no backlight, no post.
Any help would be appreciated.

[piernov]

Re: Toshiba L55-B5276 turns on, but screen is dead

You need good compatible RAM (DDR3L) for the laptop to work.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have popped in one from my own laptop, but I'm not 100% sure that it is compatible. I will have to do some research and see, if it is or not.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have took some pictures, hopefully will help to visualize better on what is going on.
When the fan runs, the current goes up to 300mA.
Fan turns on and off, as it should.
Both CPU dies heat up equally.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

Anybody?

[lapfix]

Re: Toshiba L55-B5276 turns on, but screen is dead

Can you upload the original bios or give us a link for the dump that you download

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have used this one:
https://www.badcaps.net/forum/showth...ht=toshiba+L55
It is a different model number laptop, but if I understand correctly, multiple laptops used the same motherboard.
When I get home, I can read the original BIOS as well and post it here, if it's needed.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

Do you think, that is the right one, that I should use?

[SMDFlea]

Re: Toshiba L55-B5276 turns on, but screen is dead

Both models have the same bios

https://support.dynabook.com/support...3&osId=3333728
https://support.dynabook.com/support...0&osId=3333728

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

Thanks for that. That is what I thought myself as well.
By changing the IC with the new 2.0 BIOS nothing has changed.
What do you think that I should do next?
This mobo, does not have a BIOS battery. I think that the laptop battery acts as a BIOS battery, right?
Since I don't have the rest of the laptop(battery mainly), that could cause issues?
The voltage on the coil, that is closest to the battery terminal, jumps up as I boot it, but right after that, starts lowering the voltage. Which I would assume that is normal, since it senses, that there is no battery to charge.

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

There is no fix for these Toshiba boards, since there is no schematic for them?

[tibimakai]

Re: Toshiba L55-B5276 turns on, but screen is dead

I have purchased a battery, just in case the it may be needed to boot.
It charges alright(15.2V), power led is on, fan cycles on and off as it should, I have tried two other memories and it still won't boot.
It consumes 1.2A, with battery charging and fan spinning.
What else should I check?

[emestee]

Re: Toshiba L55-B5276 turns on, but screen is dead

You wanna go component level? You gotta go component level! :-)

Do you have a POST card and an oscilloscope?

Your first destination would be the BIOS chip and the embedded controller. Test whether the power is present, and whether the EC is exchanging the SPI data with the BIOS. Assuming that's okay, your next step would be examination of EC's reset and sleep signals.