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can I use a bigger capacitor than needed?

post #1 of 14
3/29/10 at 8:41pm
Thread Starter 
right..I have a RROD Xbox 360. My error code is 0020 which means a GPU fault. I have applied the X clamp, no joy. Looking at the motherboard, there appears to be 3 capacitors that are bulging, not by much, but enough to make me suspect they are gone.
So I googles the cap numbers and comes across this:
Diagrama xbox360

page 49, all three capacitors, C5C4, C6C1 and C6C2 are in the GPU output filter..perhaps a coincidence but GPU causing RROD, 3 caps in a GPU related circuit look damaged...

but, they are a bit of odd values and I can source them but only from farnells which require a £20 minimum spend, maplins don't do them.

So, could I use higher values?
C5C4 and C6C1 are 820uf 4v, I would look to replace these with 1000uf 16v
and
C6C2 is 2700uf 6.3v, I would replace with 4700uf 6.3v

thanks in advance
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post #2 of 14
3/29/10 at 8:49pm
I wouldn't change the capacitance values, but a higher voltage wouldn't hurt.

I did the same thing with an old motherboard. Slightly higher voltage rating but kept the capacitance the same.
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post #3 of 14
3/29/10 at 8:53pm
Thread Starter 
ok ta..just found what I need on ebay and it comes to £4.08..will probably go for that. Cheers
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post #4 of 14
3/30/10 at 1:04pm
Technically though, a higher capacitance shouldn't harm anything, it's just like having a bigger buffer, or a large "reservoir" of electricity to draw from during surges.
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post #5 of 14
3/30/10 at 4:12pm
Thread Starter 
ah ok thanks but yea I went ahead and ordered exactly what I needed anyway
And then I ahem..bought another Xbox 360 today too fully working, unopened, with controller, HD component leads and power brick..and..firmware version 6683..JTAG'able and only cost me £57! the guy messed up the spelling of JTAG and put it as a one day auction..JTAG'able working boxes fetch at least £100
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post #6 of 14
3/30/10 at 10:13pm
Quote:
Originally Posted by revolink24 View Post
Technically though, a higher capacitance shouldn't harm anything, it's just like having a bigger buffer, or a large "reservoir" of electricity to draw from during surges.
Then why don't they just use 10,000 micro fared caps in everything?
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post #7 of 14
3/30/10 at 10:31pm
Quote:
Originally Posted by tjohnusa View Post
Then why don't they just use 10,000 micro fared caps in everything?
More capacitance is usually more expensive in terms of cost and space given the same technology. Also, equivalent series resistance is a concern in in some cases.

And when you move away from bulk capacitance, bigger isn't always better.
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post #8 of 14
3/30/10 at 11:27pm
Black Gates
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post #9 of 14
3/31/10 at 12:38am
Actually, in a switching power supply - which is what you're dealing with on a motherboard - the resonance of the capacitor does matter, and the circuit as a whole will perform worse if the capacitor is too big.

Basically you've got a transistor switching on and off very quickly. That transistor is feeding into a coil which, because it's a coil, has a standing electromagnetic field which discharges into a capacitor.

The circuit works best when all the components work in concert together, and a too-large or too-small capacitor can cause things to get out of sync.
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post #10 of 14
3/31/10 at 1:43am
Yeah, but shouldn't be an issue in this case as he's only replacing the bulk electrolytic caps and not the ceramic caps that would be handling that high frequency switching noise.

Long as the amount of capacitance is sufficient, I'd be more worried about ESR. More ESR means more heat, more heat means earlier thermal death, and if it's already happened once...
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post #11 of 14
3/31/10 at 2:52pm
It's not just that, but yeah, when replacing motherboard caps, replace them with the same capacitance rating, same (or slightly above) voltage rating, and the lowest ESR you can find.
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post #12 of 14
3/31/10 at 5:51pm
Thread Starter 
the correct caps didn't fix the problem anyway lol. I will get my working JTAG'able box tomorrow
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post #13 of 14
3/31/10 at 6:28pm
I have a better solution.. buy a PS3
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post #14 of 14
3/31/10 at 6:40pm
Thread Starter 
Quote:
Originally Posted by koven View Post
I have a better solution.. buy a PS3
there's always one
I've had a PS3 (only sold for monetary reasons), I bought the original Xbox 360 coz it was so cheap, unfortunately couldn't fix, so bought this one for JTAGging
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