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Damaged Notebook board.

dark666

New Member
Hi.

I have a damaged Toshiba notebook that doesn't turn on.
Checked the board for burnned marks. Found nothing, measured resistors, diodes, capacitors arround the PSU area, all fine.

If i turn the board on without the CPU it works and gives a led error stating missing CPU, found the led codes somewhere on the internet.

The only marks I see are on the transistors around the bottom part of the CPU, it appears to be a discoloration on the transistors.

The same transistros brand new are black glossy, these are really black, some of then are half back and half glossy, some are grey.

This discoloration tells me overheating and maybe they are damaged.
They are Toshiba transistors made by Toshiba for Toshiba notebooks.
I have the Datasheet for them.
Also they are quite cheap but I would like more opinions before I replaced them, not for the money, but for the trouble and time i'l waste. :rolleyes:

Please look at the photos and give opinion. :)

Thanks
 

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fingaz

Member
Hi,

If the board 'works' without the processor, I would be more inclined to think that the processor may be faulty. The only way to tell for sure it to either try that chip in another board, or another chip in that board. Having said this, if the board is faulty, you risk damaging any other chip you try in it. if the chip is faulty, you risk damaging any other board you put it in.

Neil
 

dark666

New Member
Forgot to mention!

I did test the CPU on another notebook and it worked, also tried yet another CPU on this board and the result is the same.
Same goes for RAM and Cooler, and any other hardware.

Thats how I figured mobo electronics problem.

Anyone about the transistors? :p
 

fingaz

Member
Hiya,

At least you know it's somewhere on the board. I wouldn't even like to guess about the transistors. If they burned out, you have to ask why.

You have to weigh up whether it's worth the effort if it's not successful. soldering surface mount components can be difficult if you have no experience.
If you've got the patience, and the cost of components isn't a problem, then give it a go.

Neil
 

tunedwolf

Well-Known Member
The vast majority of failures I have seen on laptop boards are shorted or low resistance decoupling caps. This sometimes also pops an smd fuse or a track. I don't remember having seen a failed VRM semiconductor, discoloured or otherwise. I have seen a few electrolytic problems around the VRM though, but it's usually really obvious with leakage or splits in the safety vents.

When semiconductors fail on mainboards, it's effects are felt throughout the system, there is hardly a module that escapes damage. If I found anything other than a piddly transistor or diode faulty, I would replace the mainboard.

Most laptop mainboards have zero ohm links or solder blob pads that allow isolation of power by section, you might want to check for shorts and then split sections off until you narrow your search down a bit.

Also, be very careful about popping and replacing components on these boards, tracks are fine and tear up easily with the slightest over temp.

rgds
 

dark666

New Member
I have a special precision soldering station just for smd components.

I was thinking, the discoloration on the transistors may have been due to overheating. But if that area overheated the CPU should be burned/damaged.
Althou CPU is more resistant to heat and has a cooler, the mobo may have shutdown before more hardware is damaged.
 

btcg

New Member
Unless it's something like a battery (used to hold hold the bios settings), always replace the motherboard - or the laptop. A computer that isn't 100% is useless.
 

dark666

New Member
The CMOS battery is fine.
Replace a notebook motherboard? It's cheaper to buy a new notebook.

Besides I'm not gonna buy a mobo for this piece of junk. Thats why I'm trying to repair.

I've repaired many, many, motherboards and VGA cards. All of them are working 100%.

If I manage to repair it, fine otherwise I'l dismantle the notebook for parts.
 

btcg

New Member
dark666,

I'm a little skeptical as to your claims.

First you say:

The same transistros brand new are black glossy, these are really black, some of then are half back and half glossy, some are grey.

This discoloration tells me overheating and maybe they are damaged.

Then, when Neil points to the possibility of a CPU problem, you say:

I did test the CPU on another notebook and it worked, also tried yet another CPU on this board and the result is the same.
Same goes for RAM and Cooler, and any other hardware.


So, taken as truth, you have a another Toshiba laptop of the same model.

Putting aside the unlikelyhood that anyone would risk damaging a working laptop by swaping parts from a damaged one, why would you rely on your eyes to diagnose a transistor/transistor block, when you can perform resistance tests on the working board and then compare your results on the non-working board?

As to:

Replace a notebook motherboard? It's cheaper to buy a new notebook.

If you've really swapped out everything you've claimed to, you've already spent more in wasted time than it's worth.

Sorry guy, but I'm from Missouri as to these claims.
 

dark666

New Member
I tested parts on another notebook, yes!
Its a risk, I know! I was willing to take it.

I've swapped out everything and yet I didn't spend any money on it because I have many, many working parts lying arround, and many working computers and notebooks for testing.

And I suspect the transistors because its the only part of the mobo that apears damaged, also I have no idea on how to test these particular transistors because according to their datasheet they are packs, inside each transistors there is a transistor, a resistor and a Zenner Diode.

Thanks
 

btcg

New Member
I tested parts on another notebook, yes!
Its a risk, I know! I was willing to take it.

I've swapped out everything and yet I didn't spend any money on it because I have many, many working parts lying arround, and many working computers and notebooks for testing.

And I suspect the transistors because its the only part of the mobo that apears damaged, also I have no idea on how to test these particular transistors because according to their datasheet they are packs, inside each transistors there is a transistor, a resistor and a Zenner Diode.

Thanks

Make a rough drawing of the transistors/transistor blocks.

Start with the working mobo:

Take your DVM in the measure resistance mode(do NOT use a Simpson 360, although I love that meter) and find a good ground. I assume you know how to use a DVM.

Measure the resistance of each lead of the transistor/transistor block. Write them down as you go.

When you're done, repeat with the dead mobo.

Any component that has a different resistance is suspect.

You can also make resistance tests across each device.

This, at least, gives you something to try.
 
Last edited:

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