Asus Z71V Will not boot ; repaired . (Verbose)
The Fault :
The laptop powers down instantly , without saving settings or hibernating . This first occurs after a period of extended use , but gets progressively worse . Eventually the laptop will not boot at all . It tries to boot but is cut off . The blue power LED illuminates for a few seconds , then dies without the drive even spinning up .
The Reason ? :
Everbody thinks the fault is in the VGA card . Some have had the card replaced and the problem has been resolved . Sometimes the problem had later recurred .
It sounds like a power problem . Something is killing the power , and is doing it for a reason ; it's not just a loose connection . So it's essential to make sure the PSU and battery are good .
It also sounds like a temp problem . A power shutdown like that is a low level action , maybe below BIOS level . It's critical stuff , like a chip hitting it's max temp .
The Z71V has a fairly restricted air path , from bottom to rear . It can get badly clogged . The fan and heatsink duct get fluffy , but the grilles at the rear are a veritable dust trap . It's easy to think you've cleaned everything out . But if you remove the heatsink and get a strong light on the grille inside it can be totally blocked without being obvious from outside .
The VGA sub-system and bridge chip are both on the same heatsink . If you remove the heatsink you'll notice two small blue pads . These are the thermal pads that transfer heat from the chips to the heatsink . Clearly they could be a lot bigger and transfer a lot more heat . The pad on the VGA chip doesn't even cover the memory chips mounted on the same sub-board . This can't be right . Memory chips get hot .
The heatsink is designed for bigger pads , almost four times bigger , so up to four times more heat could be transferred away . The assembly doesn't agree with the design . Replacing the pads for larger pieces might cure some problems , and prevent others .
In addition to a better thermal connection , the even physical pressure of a larger pad might combat one of the failure modes of SMD chips ; badly soldered pins "lifting" due to thermal expansion and contraction .
What pad to use ?
There are a few types available . I chose Bergquist Gap Pad S3000S30 in a 1mm thickness . It has a very good combination of softness , insulation , and thermal conductivity . It's soft enough to mould around the chips , maximising contact area .
The Repair :
Simply put ; replace the existing thermal pads with bigger , better ones .
NOTE that if you remove the heatsink you really should replace the pads .
Be careful when removing the heatsink . The gap pad is slightly sticky , so wriggle it off while holding the VGA card .
It is worth removing and replacing the VGA card so as to "wipe" the contacts in case some have become oxidised or low pressure .
Clean the grilles at the rear of the chassis thoroughly , get a strong light on it .
Keep everything clean , dirty fingerprints on the chips , pads , or heatsink , aren't desireable .
Cuts pieces of pad from a sheet or use pre-cut pads at least an inch square .
When refitting the heatsink place it carefully so as not to "ruck" the pad .
Tighten the screws in sequence , just finger tight , do not torque it down . Let it settle for a ten minutes , then tighten again .
After warming up a few times the screws might need tightening again , but they never need be more than finger tight .
The Result :
The laptop runs like a dream , perfecly solid . It's amazing how much cooler the keyboard is .
