Anne said:
I bought a "server" cooler from egay, one of those low and long
all-copper things, it was rated at 135 Watts.
I fitted it to my PC, and the fan whooshed like a typhoon for
about 5 seconds, then everything died. No bootee no more...
When I looked closely at the fan on this cooler, it said in
small print
12V 2.0A
I looked at some other coolers in my parts box, and they
had 0.25 to 0.6 A stamped on them...
I would have expected a rating like that, on some of the Dell
all-in-one coolers (cools case and CPU at the same time).
That sounds a bit high for a CPU cooler.
The 12V track on the motherboard, is *never* fuse protected and
the copper track in the motherboard, simply burns out when abused.
If the fan header is speed controlled, using the old method, then
there is also a danger a transistor next to the fan header can burn
out. You'd have to test all the fan headers, to get a better idea
how badly damaged the motherboard is.
Some motherboard manuals, state exactly what the fan power distribution
is rated for - if you can believe the ratings as stated.
In my opinion, you'd want to use a power adapter, once you get
to 350mA or higher. (I.e. If you cannot get specs, for what is
allowed, use an adapter to avoid the damage you've now suffered.)
*******
This is to illustrate a fan adapter. This one is good enough
for a case cooling fan, but because it doesn't handle the RPM
signal via a second connector, this cable assembly won't allow
the motherboard to monitor the fan speed. I'm not sure the
pins on the small fan connector, could even handle a 2 ampere
current flow. The small connector might be damaged. The Molex
connectors, on the other hand, are good for somewhere around
6 to 8 amperes or so (may depend on wire gauge used to make
the cable).
http://ecx.images-amazon.com/images/I/210U3tZg1nL._SL500_AA300_.jpg
Now, this cable has two small connectors on it, one male and one
female. The one with three wires, goes to the fan, while the
small connector with one wire, goes to the motherboard header
so the motherboard can measure fan pulses. This is closer to being
a useful purchase.
http://www.svc.com/pana4ptail-rpm.html
Since I can never buy just the right adapter, I sometimes make
my own. Good starting material, is a Molex "Y" cable, because
it comes with male and female connectors, wire, and can be chopped
up as you see fit. Finding crimp pins and the small plastic
shells for the fan connectors, is the hard part. I have one local
electronics store, that stocks them from time to time.
(You can get shorter ones than this. This is the Y cable, which saves
constructing the Molex end.)
http://www.newegg.com/Product/Product.aspx?Item=N82E16812706030
*******
It's hard to say why the computer won't boot. Normally, "Power Good"
from the power supply, would be handling recognition that all rails
are available. While any locally regulated lower voltages (like a 1.5V
supply on the motherboard) are monitored on the motherboard with a
power bug. So I can't say right off hand, why it won't start right
now. The 12V signal on the main power connector, powers the fans,
and may also be connected to the hardware monitor, so the voltage
can be measured. But any other usage of that 12V would be coincidental.
For example, some yoyo might build an op-amp circuit and decide
to grab +12 as a rail for the op-amp. So many theories are possible.
You'd really need a schematic for the motherboard, to make any
progress on repairing it. There is no guarantee for example, if you
soldered a wire from +12V on the main connector, to the 12V pin on
*some* of the fan connectors, that it would come alive again. If
you make a mistake in wiring, expect lots of smoke. Some of the
larger ATX supplies, can supply 12V @ 60A when given a chance - this
would be exactly the wrong time, to use a supply with a huge single
12V rail, as it'll have fun if you make a partial short on the rail.
Paul
