Asus P4B533-VM keeps blowing up caps :(

[Scenic]

Hey guys!
i'm new here. i already recapped a lot of boards, but for now i'm running out of options with the Asus P4B533-VM motherboard out of my girlfriends PC

The problems:
1. i couldnt get enough matching caps because the electronics store didnt have enough of them, so i had to mix them up with some other caps
2. it seems that someone already recapped it, but he only put 3 new (?) caps in there.

the caps near the PS2 and USB ports were 5 black nichicon 6.3V 3300µ.
but near the 12V 4pin P4 plug there were the 3 already recapped ones. 3 green KZE 16V 1200µ.
weird thing: the cap direct next to the plug wasnt a KZE, but a black nichi 6.3V 3300µ.

So i guess there were originally 3 black (blown?) nichis instead of the green KZEs.

the mainboard worked fine, but the CPUs VCore voltage jumped around from 1.85 to 1.95V (should be 1.75V for Willamette P4)
So thats the reason for the unnormal high CPU Temp...

while the board was running in BIOS (looking at the voltage and temps) i noticed that all caps near the power converters (?) get extremely hot..
i even toasted one of my fingers

so i decided to recap all of the caps near the power converters (?) and the P4 plug and replaced them with new OST 6.3V 3300µ (the only caps that the electronics store near me had in stock ) and LXZ 16V 2200µ (because the store didnt even have enough matching OSTs)

I tested the board with the new OSTs and LXZs and it still worked like before. and the CPUs VCore voltage was still jumping between 1.85 and 1.95V

i left the board running in the BIOS' Hardware monitor thingy...
after 10minutes it started smelling bad...
oops.. one of the caps (OST) got so damn hot that it popped
i replaced it with another OST... same thing after 9 minutes -.-
then i replaced it with one of the old nichis...
still got extremely hot... but at least it lasted longer until it popped (about 30minutes).

i noticed that one of the voltage converters (?) gets extremely hot within the 1st minute after powering the sys up. problem is: the cap that keeps blowing up is on the same large GND thingy as the voltage converter, so i assume the voltage conv. heats up the cap until it pops...

all of the LXZ caps get warm, but not really hot. and they dont blow up.

So what to do (except getting some higher quality caps ) ?
put some wires in there where the caps should be and place them somewhere else on the board so the voltage converters cant heat them up...

like i said before... i'm running out of options
and my girlfriend isnt really happy to wait for her pc that long...

if i had another Socket 478 board i would just replace the Asus... but i only have a dead ASRock P4i45GV which doesnt power up anymore (dunno why.. but its not because of the caps )

help :/

BTW: i'll edit the post to put some pictures in there later... battery of my cam is empty

PS: sry for my bad english...lol ^^

[Scenic]

Re: Asus P4B533-VM keeps blowing up caps

umm.. why the hell can't i edit my post?! wtf?

anyways... pics:

http://bambooz.pytalhost.net/badcaps/caps1.jpg

http://bambooz.pytalhost.net/badcaps/caps2.jpg

[starfury1]

Re: Asus P4B533-VM keeps blowing up caps

well I'll leave this to the other to explain more on but sounds like you got a shorted mosfet or short in that part of the circuit to start with and you shouldn't mix and match caps in the VRM circuit...caps have to be low ESR in the VRM

its late here.... but at this point you sound like you got more then a cap issue with it
I would not keep powering this thing up, it will result in possibly more damage
you will need to do some testing first

[Scenic]

Re: Asus P4B533-VM keeps blowing up caps

hmm... i searched for the [whatever this thing is] that gets too hot to touch.... all i found was this

http://www.alldatasheet.com/datashee...PD09N03L.html?

and after a close look at it (the thing on the PCB) i noticed that it isnt soldered on properly... i guess the guy who did the half-recap replaced it too...

hmm... i guess its easier buying a new old mobo instead of fixing this mess

[kc8adu]

Re: Asus P4B533-VM keeps blowing up caps

the shaded half circle on asus boards is positive.
reverse of most boards.
just order good caps from big pope and do it one more time...the right way!

[Scenic]

Re: Asus P4B533-VM keeps blowing up caps

i know that circle thingy. as u can see in the 2nd pic...

[kc8adu]

Re: Asus P4B533-VM keeps blowing up caps

i would do an ohmmeter test to check continuity from the + of the cap to + of the 12v 4pin
i bet that cap needs to be 16v as its on the vrm input.

[linuxguru]

Re: Asus P4B533-VM keeps blowing up caps

Yup, all the caps near the 4-pin 12v connector are probably on the +12v downstream of the inrush current limiting inductor. You'll need 16v caps there. The VRM FET could have blown, and in the process cooked the toroidal inductor LPT1, altering its saturating characteristics. The toroid looks blackish in the picture shown - they're usually encapsulated in white or yellow insulator. Compare its appearance with other nearby toroids or similar toroids on known-good boards.

[gg1978]

Re: Asus P4B533-VM keeps blowing up caps

Yup, i'd agree with the others that whoever did the board probably didn't realize they needed 16V or better caps at the VRM input.. I learned this the hard way when i did an Abit KT7A, that happens to use +12V for Vdimm input.. LOL.. Needless to say the caps there didn't last long before they domed and died..

[hardwareguy]

Re: Asus P4B533-VM keeps blowing up caps

The inductor looks fine, the wire will change color way before the toroid will. An overheated inductor will have it's winding turn reddish or brown.

The polarity can be ID'd for certain by checking for continuity with the cap terminal and the ground plane. Or you could just look at another cap that hsnt been touched....


Caps for the VRM section need to be 16V or 25V and LOW ESR or they will pop and die.

To check the MOSFET: desolder the two leads (heat them and lift them off the board, be sure it is disconnected!) while leaving the main tab on the board and test like a loose MOSFET.

[davmax]

Re: Asus P4B533-VM keeps blowing up caps

Reading thread the it would seem the correct voltage caps were installed ie 16V on VRM input and 6.3V on output. The symptoms look very like the caps are reverse connected, remembering the measured CPU voltage is less than 2 volts. Certainly this would not only blow caps but stress or fail MOSFETs.

Make sure the +12volt supply is in spec and PSU does not have a problem with caps.

[davmax]

Re: Asus P4B533-VM keeps blowing up caps

Well I have checked cap polarity against an original board photo. It is correct. With one cap always blowing so quickly it is one of several possibilities.

1. Voltage on cap is excessive.
2. Ripple current is excessive. Either all caps are not sharing the current, broken connection or one MOSFET phase has failed doubling ripple (only two phases exist).
3. Poor quality or wrong type of cap

[davmax]

Re: Asus P4B533-VM keeps blowing up caps

What I would do.
1. Make sure there is no problem with caps in the PSU.

Since one MOSFET is apparently very hot it indicates that it is working (dead ones do not get hot). Why is it hot? Either it is an incorrect replacement or it is carrying excessive load. Excessive load will be caused by either the other phase not functioning and therefore this phase takes the entire CPU load or this MOSFET is working into the other MOSFET in the same phase that has failed, causing heat and an ineffective phase.
2. Check all MOSFETs (two in each phase one large and one small) for identity and shorts. Suspect any MOSFET that is running cool.
3. Check that all the output caps are connected to together to share the ripple ie an ohmmeter must read 000 from any postive connection to any other and the same for the negative connections.
4. If the MOSFETs and caps check out OK then the VRM drive circuit may be the problem.(gets difficult).

[kc8adu]

Re: Asus P4B533-VM keeps blowing up caps

i looked at the pic and it looks like you have the vrm in/out caps switched.
that cluster of 16v caps is out of place along the cpu.
seems the one that blows up and the 2 to its right in the pic should be 16v.
follow the lead of the +12 input choke(the one with a round bar core)to the plane the 3 caps sit on.
the reason the one pops is due to it sees a double whammy.
over voltage and heat.

[davmax]

Re: Asus P4B533-VM keeps blowing up caps

KC8adu could be right.

A simple test is to put one lead of an ohmeter on the +12V pin of the 4 pin connector and with the other lead check for a circuit on the +ve terminals of the caps. Those that show up connected to +12V clearly must be the 16V caps. A similar test can be made to identify where the 6.3V caps should be. Place one lead on one side of one of the two chokes (thick wire ones) and check for connection to +ve of caps.

[PCBONEZ]

Re: Asus P4B533-VM keeps blowing up caps

If the previous re-capper got the voltages wrong the other values may be wrong as well.
-
Best thing to do is find an unaltered board for a reference as to what should be there.
-
Maybe email someone from a forum that has one.
Find some pics somewhere (eBay or a review article).
Maybe someone on bad caps has access to one to look at.

.

[davmax]

Re: Asus P4B533-VM keeps blowing up caps

Scenic. We would really appreciate what has finally been achieved. Looks like an incorrect recap. I missed an obvious clue. That odd 6.3V cap sitting with the 16V caps and it did not blow.