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Notebook Vaio: How can I be sure it's the motherboard and not the cpu?

Hello everybody from Italy,

I've this old Sony Vaio VGN-NR21ZS (April, 2008) which apparently seems dead.

The screen stays black, there is no post and no beeps, the power led stays on, the hdd led turns on for a few seconds as I attempt to turn the notebook on or whenever I press the power button - which I can still use to power off the notebook by holding it for some seconds.

Moreover the cpu fan is not spinning but the cpu, gfx and northbridge heatsinks do warm up a little.

I've tried to remove ram, hdd, dvd, wifi and modem card but still no beeps and the cpu fan stay still, not spinning. No signs from the screen at all.

I was used to use this notebook with the charger but without battery because it was broken and it wouldn't let the notebook turn on with it. Recently my father tried to turn it on with battery and charger together so it seems that made the mess.

To "repair" it at Sony Assistance I've been asked 500€: 300€ for the motherboard, 100€ for the service, optional 100€ for the battery.

I've been told by them that they don't repair parts but only replace them - this kinda made me furious.

I anyway had to pay 45€ for the poor diagnosis.

So, I would like to ask you all, how can I be sure it's the motherboard and not the cpu?

Eventually I'm willing to buy a refurbished motherboard (A1509920A) for about 90€.

Moreover, I've seen online some mini pci debug card at very cheap prices, can it be of any help?



Blank screen also on an external monitor. No Vaio logo.

I've also got the schematic of the mother board but it's still uncertain for me how to do some tests in order to replace the single fried components although I don't have any hot air soldering system or know yet any repair shop who can do it.

Answer this question I have this problem too

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4 Answers

It literally takes ALOT to kill a CPU, they dont just go bad. Have you tested your DC Jack instead of the power supply? I work at a repair shop and frequently experience a bad DC jack or the I/O chip of the motherboard going bad. It could even be you tack switch that powers on your MOBO, If you have a multimeter you can test various parts of the MOBO after watching a few youtube videos to be sure the MOBO is in fact dead.

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Thank you for your reply Jon.

Sadly the DC jack is fine, I've a multimeter and I'm looking forward into checking the singular components but despite the guides I still miss a deeper know-how for each of them (chip).

So far I've only found a decent replacement for the whole board from China, I could use the motherboard of a similar Vaio (NR38Z) but at the moment of writing I'm still uncertain about the cpu compatibility.

On the other hand, both models NR21Z and NR38Z do share the same motherboard schematic:

NR21Z: 1P-0079G00-8010 (TRIPOD)

NR38Z: 1P-0079500-8010 (HANSTAR)

Anyway, despite the fact I will probably not be able to replace the components of my motherboard, I would still like to check them.

Maybe once identified the faulty one (chip, resistor, capacitor etc) I could find somebody who can replace it.

I know it's not easy but I like more the idea of fixing the motherboard than replacing it.


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I know this seems pretty basic but have you properly discharged the MOBO without it hooked up to a power source? (Pressing and holding power tact switch for 45 seconds then letting the board sit for 20 minutes) Its a basic thing but I've actually had success with 2 or 3 systems that appeared to be dead with a simple procedure like this.

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Since the HDD led is working I think your south bridge chipset is fine, and your cpu fan is not working mean there is no power supply for cpu, It is possible for some failed components near the cpu. Start checking the voltage at Coil, Mosfet, and IC near the cpu socket.

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I have the same computer (Sony Vaio VGN-NR21ZS) with exactly the same problem.

If you have repaired yours, Luca, then I would like to know what you did.

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Luca will be eternally grateful.
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