I need troubleshooting assistance with provided schematic

[Agent24]

Re: I need troubleshooting assistance with provided schematic

EC controller (here called LPC) is U4 - W83627EHF

Oops! It is? Datasheet for that chip says nothing about EC, just super I/O controller.
Now I realise this is a desktop board - posted in the laptop section - do desktop boards even have an EC? I don't think they need one?

[atsio]

Re: I need troubleshooting assistance with provided schematic

From ISL6566 datasheet:

" VID4, VID3, VID2, VID1, VID0, and VID12.5
These are the inputs for the internal DAC that provides the
reference voltage for output regulation. These pins respond to
TTL logic thresholds. The ISL6566 decodes the VID inputs to
establish the output voltage; see VID Tables for
correspondence between DAC codes and output voltage
settings. These pins are internally pulled high, to
approximately 1.2V, by 40μA (typically) internal current
sources; the internal pull-up current decreases to 0 as the VID
voltage approaches the internal pull-up voltage. All VID pins
are compatible with external pull-up voltages not exceeding
the IC's bias voltage (VCC)"

So replace U1 again

[rookieme]

Re: I need troubleshooting assistance with provided schematic

Thank you again, I'll keep you informed as soon as I replaced it again.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

I swapped the U1 from the working board with no luck [low voltage again].
The other board works fine with the U1 from the non working one.
As I can see U1 works ok but the voltage is regulated according the VID0-4 pins.
I get the correct voltage for the VID signals I get.
So it is the VID signals that set the voltage.
U4 could be the resposible for the VID signals?

[Agent24]

Re: I need troubleshooting assistance with provided schematic

U4 could be the resposible for the VID signals?

Could be, or it's doing something to change them incorrectly. I don't know exactly how the circuit works. The datasheet I found doesn't say anything about how the VID pins work except it can read and write to them - so I guess it's maybe possible that it can change them, and override what the CPU says.

atsio said U4 was the only other place the VID signals went, so if U1 is OK then I agree it makes sense to look at U4 next.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

I swapped U4 and the working one continues to work.
The faulty one continues the problem with cpu undervoltage.
So what tells U4 what signals to produce?

[atsio]

Re: I need troubleshooting assistance with provided schematic

If i were you I would replace and Q16,Q17 and Q18

And consider and the other 8 fets on the other two phases

[ktmmotocross]

Re: I need troubleshooting assistance with provided schematic

reflow cpu socket.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

Well, new info for the issue.
At the working one, if I remove the bios [removable] I get the same "fault".
So I presume that the low voltage is regular operation [like safe mode], set by cpu if something else doesn't work as it should.
So I have a fault somewhere that prevents the normal operation of the cpu and then cpu signals for low core voltage - that makes some sense.
All I have now to find the fault, many components to try but will start from the basic ones [NB, SB]
I'll keep cpu socket reflow for the end....

[ktmmotocross]

Re: I need troubleshooting assistance with provided schematic

id signals comes from cpu through socket. have one dv6000 with low voltage. after reflow socket it work ok

[Agent24]

Re: I need troubleshooting assistance with provided schematic

Dumb question I know, but I suppose you already checked for corrupt BIOS then?

[rookieme]

Re: I need troubleshooting assistance with provided schematic

Dumb question I know, but I suppose you already checked for corrupt BIOS then?

Not dump at all, from the working one if I remove the bios I get the same failure. Yes I did made a swap as they are removable.
The fault has been found finally as it worked after reballing the NB.
As I mentioned the low core voltage was the result of an other issue.
Thank you all for your time and effort.