ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

[unmei220]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

Thanks for all the suggestions.

First I went and washed the board, since it had some thick layers of dust here and there. No luck, the board still hung at the same place.
Since now it was clean, I looked very carefully for broken traces, but couldn't find any. Really, the board is in very good condition, not a single scratch anywhere.
Then I recapped all the OST RLS 1000uf 6.3v ones with NEW KZG, same values. I tried again, still no luck, the board hangs.
Then I recapped all the OST RLZ 1500uf 6.3v ones with NES Panasonic FJ, same values. Again, no luck...
I didn't mess with the KZE or the small Ltec ones...

So, seems like another problem that isn't worth tracking down, probably related to the southbridge, as it really gets very hot when the mobo powers up. Any other ideas are welcome, but I think it simply can't be repaired, or I simply lack the knowledge to do so.

[momaka]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

What brand and model of power supply are you using?
(reason I'm asking is because I didn't see anything about this in the previous pages of the thread, and sometimes a bad power supply may cause what you're experiencing).

[PCBONEZ]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

Good question.
.

[unmei220]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

PSU used for testing right NOW is a CoolerMaster Silent Pro M 600w (RS-600-AMBA-D3) that I purchased new to replace the existing one that currently sits inside my main PC (PowerCooler PS-500SS, close to be 5 years old now). Prior to that I was testing with a recapped (with Panasonic FC) Tagan 380w (TG380-U01) that worked OK with any other things I throwed at it.
Components I used for testing this mobo works OK in another ASUS P4P800-X (Intel chipset) and MSI 661FM-L (Sis chipset) mobos I have here right now, and the new PSU works ok with all the other mobos I tested it with so far.

EDIT: do you guys think replacing the small Ltec 100uf 16v ones and the KZE 1200uf 16v will make a difference ? Also, could the remaining mosfets be the ones to blame ? I'm pretty sure the problem lies in why the SB gets so hot, problem is, I don't know what and why is causing it (for example, if something is shorted, I didn't spotted anything, if too much voltage is beign supplied to the SB, I don't know the source of it, or how to read SB voltage).

[momaka]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

Hope I'm not replying too late.

EDIT: do you guys think replacing the small Ltec 100uf 16v ones and the KZE 1200uf 16v will make a difference ?

The Ltec - maybe. The KZE are probably fine, though.

Also, could the remaining mosfets be the ones to blame ? I'm pretty sure the problem lies in why the SB gets so hot, problem is, I don't know what and why is causing it (for example, if something is shorted, I didn't spotted anything, if too much voltage is beign supplied to the SB, I don't know the source of it, or how to read SB voltage).

In those cases, check all of the MOSFETs around the SB if possible. You don't have to remove them from the board, just check for shorts between Source and Drain. Watch out for false alarms.

By the way, the power supplies you're using for testing should be fine, except maybe the PowerCooler PS-500SS since I haven't heard of that brand. Do you know who made it?

[unmei220]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

I first tried checking between drain and source on a working mobo, just to see and test what happened, and I ended up getting a lot of beep noises from my DMM, which I think means there's a short there ? But the mobo works OK, so I'm probably doing something wrong. I don't know how to test mosfets. I tried doing it in the dead mobo, and I came across 2 mosfets which didn't gave any reading at all between drain and source. I'm doing it right ? I put the DMM into the beep mode (don't know how to call it in english) to do the tests.

The PowerCooler PSU UL Registration Number is E239028, which I think means it was made by Andyson International (?). Hope that info helps.

[momaka]

Re: ASUS P4S800D-X - Won't POST, gives beep codes - Help needed

I first tried checking between drain and source on a working mobo, just to see and test what happened, and I ended up getting a lot of beep noises from my DMM, which I think means there's a short there ? But the mobo works OK, so I'm probably doing something wrong. I don't know how to test mosfets. I tried doing it in the dead mobo, and I came across 2 mosfets which didn't gave any reading at all between drain and source. I'm doing it right ? I put the DMM into the beep mode (don't know how to call it in english) to do the tests.

No, you're doing it right.

It's just that some voltage regulating modules use a set of 2 or more MOSFETs to regulate a voltage, where one MOSFET is connected between input (say, the 12v rail for example) and output and the other MOSFET is connected between output and ground. (this design allows for very precise voltages).
If the output of such a design is powering a low impedance part (a CPU for example), the resistance between that part and ground will appear almost shorted. Therefore, for the MOSFET that is connected between output and ground, Source and Drain will appear to have the same low resistance as the CPU. This may make you believe that the MOSFET is shorted when it's not, so watch out for that.

The beep mode on your multimeter is usually referred to as Continuity Check or Diode Test (most multimeters combine these two functions into one).
Continuity check/diode test is not always the best way to test if something is shorted. Reason for that being is that the beeping threshold may vary between one multimeter and another. For example, multimeter A may beep when it sees a resistance under 50 Ohms, whereas multimeter B may only beep if it sees under 10 Ohms.

For this reason, it is also a good idea to check the resistance between Source and Drain. Use lowest resistance setting for that (usually 200 Ohms on manual-ranging multimeters).

Also, post a picture of the motherboard near the SB area if possible.

By the way, the PowerCooler PSU should be good as well.