Confirm laptop CPU fault?

[sorcerer]

Got an HP DV7 (Win 7 HP; 320GB HDD and 3GB PC3-10600 RAM) in that won't boot. On pressing the power button the fan spins up and the hard drive spins up but that's it, nothing else happens - it doesn't POST and nothing ever appears on screen. The only other thing that happens is that the 'Caps Lock' LED flashes a fault code, which is on for one second, off for four seconds, and it just repeats that sequence for however long you provide power to the laptop.

According to HP's website that code signifies a CPU problem but, just in case, I've tried connecting an external monitor, substituting the RAM with known good sticks, a known good hard drive and a known good charger to no avail.

Googling shows that a new CPU has indeed fixed it for some people but others have bought a new CPU and it hasn't cured the problem - in their case it's been the GPU/mobo with some going on to find success with a reflow or reball.

I've just looked on Ebay and can get a brand-new AMD Phenom II HMP820SGR32GM (Socket 1) processor for £34 which isn't a lot of money, but when there's not a lot coming in I can't really afford to waste it either. Is there any other test or anything else I can do to help me confirm it's the CPU at fault?

 

[NYJimbo]

In my years of experience with the DV7 (1000-7000) almost every machine that showed a faulty CPU was really a faulty BGA chip.
If you can get the customer to pay a non-refundable new CPU and tear-down fee, then I would go for it. Otherwise I would NOT even bother. Just be sure you have checked everything else, we have seen false positives on CPU error light for bad ram or shorted cables.

This is a common problem for most of the pav line (especially dv4, dv5, dv7,dv6000,dv9000, hdx-16, hdx-18)

 

[AndyM]

In my years of experience with the DV7 (1000-7000) almost every machine that showed a faulty CPU was really a faulty BGA chip.
If you can get the customer to pay a non-refundable CPU and tear/down fee, the I would go for it. Otherwise I would NOT even bother. Just be sure you have checked everything else, we have seen false positives on CPU error light for bad ram or shorted cables.

^^^ This.

Had a HP in recently, exactly the same symptoms. Faulty BGA.

Andy

 

[sorcerer]

Thanks very much for your very quick replies guys. I love Technibble

 

[wavey]

Yep, almost certainly GPU failure (overheating, poor design) you could reflow but it will fail again.

 

[AndyM]

Yep, almost certainly GPU failure (overheating, poor design) you could reflow but it will fail again.

I tried a reflow. Worked for something like 4 hours. Only other option is a new motherboard, but seriously, why would anyone bother?

Andy

 

[sorcerer]

I tried a reflow. Worked for something like 4 hours. Only other option is a new motherboard, but seriously, why would anyone bother?

Andy

Even a new motherboard would only cure it for a limited amount of time. I once seriously considered throwing £2 - 3k into the equipment and setting up for reballing/reflowing work (thankfully didn't in the end) and during the research I found out that manufacturers don't do 'spare parts runs' as such. All spare parts are manufactured during the main production runs so any inherent fault or design problem is still present in any spares you buy later on.

 

[buzzcut]

reflow won't last, it's junk reminds me of an Acer Aspire 5520 it would power cycle.
Reflow GPU lasted 1 year, 2nd time lasted a month.

 

[AlaDes]

When I receive a fault code indicating a faulty CPU, I simply do the "power it on, wrap it up tight in something that will overheat it, and leave it setting for about two hours" trick. I then power the unit off, unplug it, and remove the battery. If it powers on after that, it's definitely the GPU and not worth repairing, although I have had a few customers bent on going against my recommendation.