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Motherboard caps

P

purtnoy

Jan 1, 1970
0
Just replaced all the 2700 micr 6.3 volts, with 3300 mic 16 volt caps
(the 3300 caps are twice as big around,(does that matter?) had to
solder longer legs to raise them up, so they can fit without shorting
them out. replaced a few other smaller caps also...........still the
same as before, when I hook the power supply to the motherboard, 2 red
lights glow on the motherboard, the CPU fan turns, power supply fan
turns. when I hookup the monitor to the video card,the screen will
not come on, green light just flashes, (monitor is good works with
other computer) video card is good, and the ram is good.
 
A

Antoine Deschênes

Jan 1, 1970
0
purtnoy a écrit :
Just replaced all the 2700 micr 6.3 volts, with 3300 mic 16 volt caps
(the 3300 caps are twice as big around,(does that matter?) had to
solder longer legs to raise them up, so they can fit without shorting
them out. replaced a few other smaller caps also...........still the
same as before, when I hook the power supply to the motherboard, 2 red
lights glow on the motherboard, the CPU fan turns, power supply fan
turns. when I hookup the monitor to the video card,the screen will
not come on, green light just flashes, (monitor is good works with
other computer) video card is good, and the ram is good.

Sometimes there's a poor connection between mainboard and ram or Video
card and ram. Try with an other card. Or, maybe because the bigger caps
take more time to charge, the video card can't take it. Try to power on,
wait and reset.
 
H

Harvey

Jan 1, 1970
0
purtnoy said:
Just replaced all the 2700 micr 6.3 volts, with 3300 mic 16 volt caps
(the 3300 caps are twice as big around,(does that matter?) had to
solder longer legs to raise them up, so they can fit without shorting
them out. replaced a few other smaller caps also...........still the
same as before, when I hook the power supply to the motherboard, 2 red
lights glow on the motherboard, the CPU fan turns, power supply fan
turns. when I hookup the monitor to the video card,the screen will
not come on, green light just flashes, (monitor is good works with
other computer) video card is good, and the ram is good.

Is the CPU getting warm?
 
J

James Sweet

Jan 1, 1970
0
purtnoy said:
Just replaced all the 2700 micr 6.3 volts, with 3300 mic 16 volt caps
(the 3300 caps are twice as big around,(does that matter?) had to
solder longer legs to raise them up, so they can fit without shorting
them out. replaced a few other smaller caps also...........still the
same as before, when I hook the power supply to the motherboard, 2 red
lights glow on the motherboard, the CPU fan turns, power supply fan
turns. when I hookup the monitor to the video card,the screen will
not come on, green light just flashes, (monitor is good works with
other computer) video card is good, and the ram is good.

It's possible something else fried on the board when the caps failed.
 
G

Gerard Bok

Jan 1, 1970
0
Just replaced all the 2700 micr 6.3 volts, with 3300 mic 16 volt caps
(the 3300 caps are twice as big around,(does that matter?)

Yes. In this case it does matter.
In lineair systems, 'bigger is always better'. On your
motherboard exceeding a capacity value by 50% could disrupt the
entire regulator circuit.
Basic operation in this case is based on energy stored in an
inductor, periodically transferred via a (schottkey)diode into a
low ESR capacitor.

You can only replace those capacitors with types of roughly the
same value, high temperature types and --at least as important--
low ESR values.
had to
solder longer legs to raise them up, so they can fit without shorting
them out.

That also is unacceptable. This will introduce an extra induction
('coil') in series with the capacitor. Take a look at the coils
surrounding those capacitors. And notice that they only have a
few turns, hence very low inductance :)

The circuit you are working on is likely to be the CPU stepdown
regulator. That is a circuit that transforms 12 volts into
something like 1.55 ... 2.55 volt. At several amperes.
 

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