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Old 06-06-2015, 06:57 AM   #1
lbwlow
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Default Asrock P4i945GC

I am attempting to fix this Asrock P4i945GC mobo, I found a bad caps near the CPU. I have tested the mobo with the bad caps still on it, without RAM, it will give beep code of no RAM. With RAM on the mobo it won't beep, but there is no display. After a few minute with the system turned on, the choke slowly heating up till the point where it is untouchable, the bad cap is the one which is the hottest. The underside of the PCB has been discolored due to the heat i guess.



After replacing the caps, the mobo still the same as before the caps were replaced. The replaced cap was still very hot to touch, now i am guessing it was the choke/vrm's fault, is there any way to test them? Is super hot choke a symptom of failure ?





Thanks, any help is appreciated
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Old 06-06-2015, 07:42 AM   #2
stj
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Default Re: Asrock P4i945GC

what caps did you use?
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Old 06-06-2015, 08:00 AM   #3
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Default Re: Asrock P4i945GC

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Originally Posted by stj View Post
what caps did you use?
ChemiCon KZJ 1800uf 6.3V
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Old 06-06-2015, 08:25 AM   #4
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Default Re: Asrock P4i945GC

looking at the last foto, the coils probably need resoldering.
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Old 06-06-2015, 11:27 PM   #5
lbwlow
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Default Re: Asrock P4i945GC

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Originally Posted by stj View Post
looking at the last foto, the coils probably need resoldering.
Those circled in red are capacitors and yellow are coil. I have checked, i am pretty sure the solder are just fine, they appear to be black due to bad lighting.


UPDATE: The next morning I turn on the motherboard and it appears to be fine, I left it untouch since last night.
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Old 06-08-2015, 11:48 PM   #6
momaka
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Default Re: Asrock P4i945GC

Quote:
Originally Posted by lbwlow View Post
ChemiCon KZJ 1800uf 6.3V
That's like replacing a flat tire with a slightly less flat tire. Chemicon KZJ and KZG are known to have *many* problems on motherboards. Avoid!

Also, there may be other Ost caps on the board that are bad. You need to do a full recap on the motherboard. Post more pictures of the entire board so we can see what you are seeing.

As for the hot VRM - it might be because it is designed badly or because those brown Chemicon caps on the input are bad too. If they are KZG, replace them. If they are KZE, you can leave them alone.

Since the VRM coils are rated for fairly low inductance, you can probably do a polymer mod (i.e. poly mod) here. 820 uF 2.5V/4V/6.3V polymer caps should work great here.
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