Gigabyte 8S661FXM-RZ

[davmax]

This came in with badcaps in PS and VRM input. No boot.

Replaced caps still no boot. Problem is in VRM\CPU area. VRM output 0.57V with no CPU present but fan connected. 0.06V with CPU present. Have checked for shorted caps, none. Have checked for shorted or melted MOSFETs , none.

I suspect CPU is burned fan and heatsink clogged with dirt (now clean) there appear to be some hot spot colours on the top of the CPU, green at centre flairing out to black then brown, like a spark burn.

I expected the VRM output to be higher with no CPU load. Is VRM output stable with no load??? What voltage should be expected??

CPU is 478 Celeron 2.4Ghz. Vcore spec 1.25-1.4

Comment please

[davmax]

Re: Gigabyte 8S661FXM-RZ

Forgot to state that 12Volt supply to VRM is OK

[davmax]

Re: Gigabyte 8S661FXM-RZ

I suspect that removing the CPU is not a good test of VRM in that I believe the CPU is involved in setting the core voltage. Is this right? I do not want to rush out and get another CPU without some confirmation that VRM is OK as components suggest.

[kc8adu]

Re: Gigabyte 8S661FXM-RZ

measure cpu core across the mlcc on the underside.
best way to detect shorted core.
vrm output is set by vid pins.
different steppings need different vcore so intel sets up vid pins to suit.

[davmax]

Re: Gigabyte 8S661FXM-RZ

kc8adu thanks.
I have been measuring core at VRM output caps. I guess this is close. It has been effective with working systems. Certainly pulled low by CPU in this case.
I think I read you correctly that CPU sets voltage via VID pins.

It therefore appears CPU is toast. Do you agree?

[starfury1]

Re: Gigabyte 8S661FXM-RZ

if I understand about VRM from what I read in a zillion page pdf on it
yep the cpu tells it via vid what voltage it requires

Anyway a quick search found a wiki

The correct supply voltage is communicated by the microprocessor to the VRM at startup via a number of bits called VID (voltage identificator). In particular, the VRM initially provides a standard supply voltage to the VID logic, which is the part of the processor whose only aim is to then send the VID to the VRM. When the VRM has received the VID identifying the required supply voltage, it starts acting as a voltage regulator, providing the required constant voltage supply to the processor.

Wikihere

not much else of any real use there...intel link maybe

HTH and yeah I'll leave it to KC8 if its stuffed or not
(not the guru here, my guess probably)

Cheers Davmax..and were you been hiding? all

[shadow]

Re: Gigabyte 8S661FXM-RZ

I suspect CPU is burned fan and heatsink clogged with dirt (now clean) there appear to be some hot spot colours on the top of the CPU, green at centre flairing out to black then brown, like a spark burn.

That really does not sound healthy! It seems like something has been getting whatever is at the black and brown coloured areas quite hot. My guess would be that the CPU is toast. A sure way to find out is to test the CPU in a known working motherboard, although a lot of the time this is not possible. A picture may be helpful if possible.

[starfury1]

Re: Gigabyte 8S661FXM-RZ

Akor posted a VRM checking procedure (how applicable it is don't know, possibly you have already done this) and the other thing that crossed my mind was Possibly The MB my have become a CPU killer
there is a thread Identifying a CPU killer (ahead of time) help
maybe you have all read done this too but thought Id add it anyway....

your dead (clogged) fan and over heated CPU, might really be it most likely.

Another idea is to possibly identify the VRM controller chip (possibly support chips) and grab the pdf for it so you can get a better idea of how the VRM is put together on that PCB.

Like I said, not the guru... just trying to help in my own small way

cheers all

[davmax]

Re: Gigabyte 8S661FXM-RZ

starfury1. Many thanks for links. Useful. I have now identified the problem as VRM failure and I am replacing the motherboard. Getting a better one with Intel chipset and dual mem controller, better for customer.

[starfury1]

Re: Gigabyte 8S661FXM-RZ

No worries Daxmax glad I was of some help

Cheers mate

correction for my above post..."already done this"...DOH!

[krazykev64]

Re: Gigabyte 8S661FXM-RZ

i also got one of these and i can see for sure that the caps are gone as three are bulged. as a matter of interest was the three caps between the agp slot and heatsink mounting made by rubycon or have they been replaced in the past. can all caps be purchased from maplins?

[kiddznet]

Re: Gigabyte 8S661FXM-RZ

I have an identical problem with a 8s661fxm-rz socket 478 board
Did anyone resolve this one?