change motherboard in emachine c2684

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I have an Emachine C2684 (AMD/NForce2) PC that now fails to post. All
evidence points to a bad motherboard since the AMD 2600+ tests OK on a Soyo
Dragon kT333. When the box is plugged in the CPU fan starts turning
immediately, but the system is dead when turned on with main button. Nothing
but the CPU fan powers up -- neither the hd, nor any system LED's turn on.

I have ordered a Biostar M7NCG MicroATX board.

Is the OEM power supply expected to be compatible?

Any caveats or advice would be greatly appreciated. I have a couple more
days before the board arrives.


Re: change motherboard in emachine c2684

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Although the Emachine PS should work Ok...
they tend to be you may want to upgrade that too.

Since the mobo is not identical to the may have to perform a
repair installtion.

NOTE: If you have a factory restore will not work...
as it would be tied to the original mobo

Re: change motherboard in emachine c2684

On Sun, 25 Jun 2006 20:21:18 GMT, "tlviewer"

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Have you ruled out the power supply?
That's one place eMachines have been known to cut corners
and are a common failure point- have been for years in
emachines.  That the system shows partial signs of power
doesn't necessarily rule out the PSU.

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presuming it is standard ATX, yes, BUT:

Does the original motherboard use the 12V, 4-pin connector
from the PSU?  If so, you may have an incompatibility
because that suggests the original board used 12V current
for the CPU (stepped down on the motherboard, but 12V is the
original source of this current).   M7NCG is a decent board
(for a 2nd tier brand) but uses 5V for CPU power, meaning
that if the original PSU were a modest rating and was
optimized to provide mostly 12V power, you would now be
asking it to provide mostly 5V power and it may not be able
to comply, or may not be able to do it long-term.

You "Might" be ok though as M7NCG is an integrated video
board, integrated sound and nic too so for an Athlon XP
system it's 5V power consumption will be lower than some,
providing you dont' have a lot of other power hungry things
plugged into the board, nor a lot of other (drives or USB)
devices... though these latter two don't use a "lot" of 5V
current but if you're near the max every amp might count.
It is conceivable that a good mATX PSU optimized for 12V
current wouldnt' even be able to turn on the system with the
M7NCG in it.

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I have one of those boards and for an all-integrated mATX
nForce2, it's a  pretty good value.  One thing I noted was
that it was most stable at a (bios) setting of CAS2.5 for
the memory.  That is, even with memory rated for CAS3, a
setting (or auto-detect/SPD by the board) would result in
errors at CAS3 but if it was manually set to CAS2.5 it runs
like a top.  I am suspecting that this is a cosmetic flaw in
the bios, that someone transposed the 2.5 and 3, values such
that when 2.5 is selected then 3 is actually used and
vice-versa, as otherwise it makes no sense that it would be
more stable at 2.5 than 3 with standard cas3 memory in it.
Unfortunately I never got around to benchmarking both
configs to see if this appeared correct but then again I
dont' even recall if it was stable enough at cas3 setting to
boot anything at all to run such a benchmark.

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