Cpu core voltage low

[mjtech]

Hi all,
PREVIOUSLY I MENTION THIS PROBLEM IN VCOR SHORT THREAD NOW I AM
CREATING NEW THREAD

I am working on a industrial motherboard shb110 .
It has c2d processor(on board), 945 chipset,ich7.

Isl 6537a for gmch and ddr section 1.5v and 1.8v
and isl 6262 for cpu core section.
Sio w83627hg-aw

problem in this motherboard is , its not booting, cpu voltage is coming 0.7v , which should be 0.9v to 1v as per reading from working board

gmch, ddr, vtt_gmch all voltages coming properly.

Isl 6262 ic giving pgood and clken# signal properly which means ic is ok.

Pcirst signal is also coming.

Now i am stuck at this 0.7 v problem ....
Is it a problem of cpurst signal or cpu it self. Or else ...

Please anyone can guide me in this problem please....

Thanks in advance


REPLY FROM
piernov
Badcaps Veteran

Check CPU VCore capactors, check voltage of VID0 to VID6 pins of ISL6262. Make sure you use a good and compatible CPU.

[mjtech]

Re: Cpu core voltage low

Thanks pieron for your reply

i replaced vcore capacitors, i also replace smd caps in isl 6262 section , but same result....!
Cpu is onboard i can't change the cpu.

Voltages from vid0 to vid6 are 1011010

vcore voltage is still 0.7v,expected 0.9v to 1 v

dose cpu required any feedback signals?(cpuslp signal)

pltrst signal is prersent i measured it on sio pin 30.

Anyone have schematic for shb 110 motherboard?

Please guide me, what should i check further?

Thanks

[piernov]

Re: Cpu core voltage low

As per IMVP-6 specs, VID 0101101 (from VID6 to VID0) should give you a voltage of 0.9375V. I'm not sure why it would be 0.7V.
Maybe there is an issue with the feedback circuit, but without schematics it will be hard to find. If the resistors on the board have a value written on them, check them. Otherwise you may be out of luck.

[Th3_uN1Qu3]

Re: Cpu core voltage low

Replace ISL6262, i've seen a few that were acting up in weird ways.

[mjtech]

Re: Cpu core voltage low

Thanks guys for your reply...!!!
Finally i decided to replace IC ISL 6262 as TH3_uN1Qu3 said.

and guess whattttttt...!!!! PROBLEM SOLVED.....!!!!!!MOTHERBOARD IS NOW BOOTING PROPERLY. THANKS ALOT....!!!

I have one more same motherboard in which lower mosfets of core section was showing dead shot so i removed those mosfets and checked out circuit, found mosfets are fine , so i assumed isl 6262 may be faulty...

so i replaced that ISL6262 IC also......shorting proble resolved.....motherboard start working.........but after testing of 20 min when i restarted the motherboard, problem occured...motherboard is now not booting.....voltages are present but no booting..

in cpu core section 0.9 v (which goes till 1.0v while booting in working board)
ddr voltage is 1.8v
gmch voltage 1.5v
vttt_gmch 1.08v

i replaced the ram also, pltrst signal is present , but cant measure pcirst since pci slot is not regular one , pin outs are different.

i also observed that in core section resistance between gate and source of both upper mosfets differs by approx 27 ohms(upper1 930 ohms, upper2 957 ohms) but in working board there is no difference in resistance of both upper mosfet's gate and source.
all four mosfets in core section are ok i tested them out circuit

now what should i check next?
how to confirm if ram is detecting properly or not?which signals should i check and where ?
please guide me....