Re: Bad Motherboard? No Power
- From: "larry moe 'n curly" <larrymoencurly@xxxxxxxxxxx>
- Date: 4 May 2006 14:42:01 -0700
gtslabs wrote:
When I jumper the MB Green wire pin 14 to Pin 13 black wire then the
PSU works and all the fans turn.
I have continuity across the switch when depressed. I pulled the switch
pins and shorted but still no power up.
I see no burnt out capacitors.
I tried to power up by removing all power leads to HD,FD,CD, DVD. No .luck
CPU fan turns freely.
I determined I have a MSI 845 Ultra-C MS-6566 Motherboard.
I removed the CPU fan and heatsink and noticed that the gray coating
from the P4 Chip has worn off and transfered
to the aluminum contact surface of the heat sink. Is that typical?
All P4s I've seen had a silvery coating, not a grey one, and any grey
stuff was thermal grease, but it's normal for that grease to come off
when the heatsink is removed.
Could the CPU fried from too much heat and that be the reason the MB
wont energize?
P4 chips have built-in protection against any overheating not caused by
a blowtorch.
I found a replacement MB for $36 refurbished but wanted to check out
the CPU problem first.
If this combination is not cooling the CPU enough then maybe I should
consider something else.
The problem started a few months after I installed a "NEW ATI RADEON
9600 SE 128MB DVI VGA AGP 10588" video card for my son
to run some game.
Is it possible that your PSU's +5.0V or +3.3V rail has gone bad because
of bad output capacitors or diodes? When you short the green and black
wires together, do you get any voltage when you connect a meter between
any black wire and red wire (+5.0V) or between a black wire and an
orange wire (+3.3V)? Don't be too concerned if those voltages are off
by 10-20% because that can be normal without a load. Diodes usually
short when they fail (so do transistors, and sometimes you find them on
the outputs, especially the +3.3V) and will cause AC to come out the
rails. I don't know if this will damage the PSU's output filter
capacitors or the mobo, but I'd first try another PSU, initially
without a CPU in the mobo but with the green PSU wire shorted to
ground. Then I'd measure the voltages on the mobo's MOSFETs and
Schottkys because on some of their pins you should find +12V from the
PSU, and on some other pins the CPU core voltage. Stick pieces of
cardboard between the MOSFET and Schottky pins to avoid shorting them
with the meter lead. What PSU do you have? Internally does it look
more like this, heft-wise:
http://static.flickr.com/43/73954319_bc8f9de6d0_o.jpg
or this:
http://static.flickr.com/37/82654518_a55fb37001.jpg
.
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- Bad Motherboard? No Power
- From: gtslabs
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- From: gtslabs
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