Alec wrote:
> Paul,
>
> Quite right, I believe. I realized that the person who originally
> built this system (not me) had bought a power adaptor for the fans and
> even had some variable resistors to control their speeds for quietness
> and reduced power consumption. So last night, I came to that
> realization, plugged them all into the disk power and voila, the fans
> worked. With that behind me, I booted the computer, which made it to
> the windows startup screen but never successfully started up past that.
> I assumed that my hard drive had become corrupted somehow and that I
> would have to reformat it, so I downloaded a linux install disc that I
> planned to use today. Fast forward to ten minutes ago, at which point
> I tried to start the computer again to boot from CD, only to find that
> now the computer will not even POST, even with only the (assumedly)
> working CPU and new RAM on the board (it should give me a beep code to
> tell me the video card is missing). I'm assuming that the
> possibilities here are: that the CPU overheated sometime last night but
> the BIOS did not shut the computer down; that the BIOS is corrupted
> somehow; or that the motherboard is just indiscriminately broken.
>
> If you have any ideas or tests that I could run (aside from bringing
> the mobo to a repair shop, which would probably cost nearly as much as
> just buying a new one), I'm all ears. FYI, I believe the BIOS is an
> Award 1.06 or something close to that. Like I said, I was able to
> POST, edit and save the BIOS configuration options, and get to the
> initial Windows startup screen last night with no problems, but this
> morning, after no changes since last night besides assumedly the
> temperature of the board, the system will not even POST.
>
> Alec
If the CPU fan was not running, and the machine was left running
in that state, it is possible the CPU is fried. You can try disassembling
it, and check the CPU silicon die for discoloration. Sometimes a
fried processor, will also leave a mark on the heatsink.
You could try clearing the CMOS on the board, but in this
case, if cooling was missing, the CMOS is not going to
magically revive it. In the event of a cooling mishap, my
first impulse would be to remove the heatsink, clean up
the silicon die with some rubbing alcohol, wait for it to
dry, then apply fresh thermal paste. Then, *carefully* fit
the heatsink back on it. If there are signs of physical
damage, that may be enough to stop you in your tracks
right there (i.e. if the die is cracked, you won't have
a good reason to put it back together).
For processors with a bare silicon die, one thing to watch
for, is that the heatsink is not tilted while assembling it.
The silicon is brittle, and you can crack the edges of the
silicon die, while trying to get the heatsink back in
place. That is one reason I use a Zalman 7000 cooler on
my AthlonXP, because it is fastened with screws, and it is
easier to put back together than a heatsink that uses
a clip.
One aid that can protect the silicon die, is a rubber gasket
that is the same thickness as the silicon die, and forms a
ring (with hole in the center) around the silicon die. With
a gasket in place, it is harder to tilt the heatsink and
damage the silicon die. But if the gasket is slightly too
thick, it takes extra assembly pressure to compress the
gasket.
If it turns out you fried it, you may be able to find
another processor on Ebay. The supported CPU list is
here:
http://support.asus.com/cpusupport/c...=en-us&cache=1
Modern processors have two levels of thermal protection.
The first thermal point, causes throttling (CPU slows
down). If the temperature continues to climb, THERMTRIP
causes the power to be switched off on the computer. But
on some of the older Athlon motherboards, there was little
in the way of effective protection.
My A7N8X-E Deluxe actually has a small 8 pin chip near
the processor, and its job is to check the CPU thermal
diode voltage. That chip will turn off my computer,
in the event that the heatsink falls off my AthlonXP.
The thermal diode is a good way to monitor processor
temperature, as the diode reacts instantly in the
event of a temperature change. On Athlon64 products,
chips like that aren't necessary any more, as the
function of that 8 pin chip is now inside the processor.
Paul
>
> Paul wrote:
>> Alec wrote:
>>> via the title: "a7m266 w/ 1.4ghz athlon will post, but fans do not
>>> spin"
>>>
>>> That is, the computer will boot, and I can get into the bios, and the
>>> fan for the power supply will spin, but neither the "power fan",
>>> "chassis fan", nor "cpu fan" will spin at all, not even momentarily.
>>> The system was previously non-functional (non-POSTing), but after
>>> leaving it overnight and then removing all the PCI cards and unplugging
>>> all the hard drives it seems to boot now, but still no fans spinning.
>>>
>>> Any ideas of things to try to get the fans working? I've reset the
>>> CMOS, loaded factory setup defaults in the BIOS, etc. Tried each of
>>> the fans individually. Any help would be appreciated.
>>>
>>> Thanks,
>>> Alec
>>>
>> I don't think the +12V that feeds the fans, is fuse protected. You
>> may have burned the 12V copper track feeding the fans.
>>
>> http://www.amdmb.com/images/a7m266/a7m266-a7m266.jpg
>>
>> For testing, I would start with an ohmmeter. Unplug the fans, switch
>> the meter to ohms, and measure from the +12V pin on the main power
>> connector, to each fan header. As I don't see a switching transistor
>> near the CPU fan header, most likely the power is supposed to be
>> a direct connection. So the ohmmeter should read zero ohms if the
>> +12V track is intact. You can also check the ground pin on the fan
>> headers as well, but I would expect the ground to be a much better
>> connected pin than the +12V. The +12V is probably carried by a fairly
>> thin track on the surface of the motherboard. If something is going
>> to fail, it would be the +12V track.
>>
>> You can buy "disk drive to fan header" adapter. Plugging each fan
>> into its own adapter, will give you working fans again. That is what
>> you do, when something in the fan header gets burned out. (That
>> basically bypasses the burned copper track.)
>>
>> Paul
>
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