HP Elitebook - video issue

[blazzelia]

Hello everyone,

My laptop, an HP Elitebook 8460w with Radeon HD 6490M video chip, has died. One day it went black after doing some weird multicolor lines on the screen and it came back after a restart, the next day died for good (similar weird lines).

Following the schematic of the laptop and the board view I was able to narrow the issue to the video chip. I noticed that the chip power, +VDD_CORE is zero so I separate the chip power from the rest of the motherboard (there is a pad on the motherboard which allows this) and inject 0.85V in it. I start with a small current but eventually I reach 1.9A and voltage went to 0.35V. At that point it didn't take more current.
I was hoping to find anything - the chip or the remaining discrete components - that would heat but the temperature is kind of uniform and low on the whole area. I couldn't find any spot there that would jump above 27 degrees Celsius.

Is this something that anyone has seen before? Should I blame the chip?
Any idea is most welcomed.

Thanks,

B

[Smith]

1. Have you tried reseating the memory, or use just one bank?  Had simmilar issues with a same generation HP once.
2. Have you tried disconnecting the lcd cable from the mainboard, and try an external monitor? The cablebor display may have a short (happened to me once, the LVDS cable had a short)
3. If all else fails a new BIOS flash could help. Had a similar generation HP laptop with a bad eeprom. It had a lot oftypes of failures. You should find a ROM file eeprom, the HP eeprom programs only flash a part of te eeprom. Watch out with different types of EEPROMS for the same type oflaptops with different types of graphics cards.

[blazzelia]

Hi,

Yes, I already tried pct. 1 and 2.

At this point the video chip power is separated from the rest of the motherboard and the multimeter indicates a short circuit of the chip power pins to the ground. So it's one of the followings:
- video chip internally shorted
- one or more of the very small capacitors from the top of the chip shorted - really small and very hard to work with without a microscope
- the short is under the chip between the BGA balls but I'm not sure that's a real physical possibility being the size of the BGA balls, the distance between the chip pads and the distance between the motherboard and the chip. Someone with experience could tell more about it.

I'm not sure how a BIOS flash could help in any of the above situations.

Thanks,

B

[Smith]

Like i said, one elitebook had weird issues, and a new BIOS flash solved these, as strange as it was.

I would try capacitors first, they are more likely to fail.

If it is your graphics chip there might be another solution. If you can remove the grahics chip and your cpu had built in graphics and there is an similar elitebook without the radeon chip you might be able to flash that EEPROM and make it work that way.