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Old 06-04-2019, 03:31 PM   #1
eic_2019
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Default What do these motherboard caps do?

Hey guys, I'm trying to learn more about circuits and am wondering what the 3 circled capacitors are responsible for on my computer motherboard. They are all 6.3V 3300uF Rubycon MCZ. The computer wasn't able to start-up until I got these 3 replaced. Thanks in advance!
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Old 06-04-2019, 05:23 PM   #2
stj
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Default Re: What do these motherboard caps do?

power smoothing - probably for the cpu.

i see there are some similar ones - keep an eye on them incase the rest fail.
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Old 06-04-2019, 05:26 PM   #3
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Default Re: What do these motherboard caps do?

Your MB has DC-DC converters on it to regulate the proper voltage for your processor and memory. Those are probably the output filter capacitors for that DC-DC converters. They need to be ultra-low impedance types. They also do do well with heat, so be sure your cooling is good and vents in the case are not obstructed by being against a wall or next to tall stuff.
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Old 06-04-2019, 05:45 PM   #4
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Default Re: What do these motherboard caps do?

This might help explain the vrm circuit on the motherboard https://www.maketecheasier.com/what-is-vrm/
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Old 06-05-2019, 08:36 AM   #5
eic_2019
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Default Re: What do these motherboard caps do?

Thanks for the replies guys! I appreciate it a lot!
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Old 06-05-2019, 07:01 PM   #6
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Default Re: What do these motherboard caps do?

They're part of the DC-DC converter which takes 12v (from the 4pin cpu power cable) and converts it to ~ 0.6v..1.4v, as the processor demands.

Because the power supply can react slowly to variations in power consumption (for example imagine alt-tabbing from a game into Windows and back, the processor's power consumption may go from 10 watts to 60-100 watts in a second because modern processors dynamically adjust the core frequencies or even turn off cores when not needed), those input capacitors act like buffers, they store a bunch of energy and help the dc-dc converter function without hiccups until the power supply reacts and recovers, pumping energy into the capacitors refilling them.

It's more complicated in reality, like the wires between power supply and motherboard acting like inductors, they also have some resistance so there's some power loss in the wires themselves... and other things.

But basically, think of them like a big fuel tank where fuel trucks constantly come to dump their fuel inside the tank and the processor's dc-dc converter can vary how much fuel takes, as needed, because there's always gonna be some reserve in the big fuel tank.


The capacitors on the left side in the pictures, the shiny ones which have 560 written on them, have the same purpose but on the output side, where there's a lower voltage, usually less than 1.5v
They smooth out the voltage going to cpu, when the cpu's power consumption can fluctuate hundreds of time a second.
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