I need troubleshooting assistance with provided schematic

[rookieme]

The first issue was that couldn't power on.
Q15 was shorted so I replaced it and it was burned/shorted again as soon as I powered it on.
Replaced Q15 again and U1 at thee same time that it is it's controller and driver [parts from a scrap motherboard].
Now it powers on but doesn't boot, nor cpu fan spins.
The VCCP cpu's core voltage is 1,08 V that is not correct.
At same working board is 1,28V.
Any guess what could be going wrong?

Thank you in advance

[Agent24]

Re: I need troubleshooting assistance with provided schematic

I can think of two ideas you could check out:

1)If Q15 had shorted, then that would connect CPU VCCP to +12VP_FET rail, the CPU might be damaged now from overvoltage.

Have you checked the CPU is still OK in another board?


2) It seems odd that the fan doesn't spin. have you checked the fan control circuit (Page 27) is getting all the power rails it needs and any enable signals, etc? If the fan is dead because another rail somewhere is dead, it might be why VCCP is wrong and the system is not starting.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

The cpu hopefully works ok at another board.
I don't know how to check the fan control signals but I'll check the voltages.

Could it be capacitor issue?

[Agent24]

Re: I need troubleshooting assistance with provided schematic

The cpu hopefully works ok at another board.

I don't fully understand what you mean. Does it work in another board or do you hope it works?

You should check that the CPU is OK first, because if the CPU is dead you may be chasing a non-existent fault on the motherboard.

I don't know how to check the fan control signals but I'll check the voltages.

The fan is PWM controlled by the line FAN_CTL1 from U12, the ADT7475 fan controller chip. On this line you should see a square wave if you have a scope. If you don't have a scope, it should show a voltage probably around halfway between the chip supply voltage of 3v - IF the signal is present.

This FAN_CTL1 signal (if present from U12) needs to get to Pin 2 of U9A. Also check that the voltage at Pin 3 of U9A is OK. It should be around 3v.
If Pin 2 is at 3v as well, the opamp will set a low output, turning on Q12 and supplying power to the fan. If the fan is not going, I suspect FAN_CTL1 to be at 0v.

You need to check that signal at both sides of R165. It could be that U12 is generating the signal but it is not getting to U9A.

Could it be capacitor issue?

If the decoupling capacitors for the main voltage rails went bad, I guess it could maybe cause the problem (bad capacitors can do all sorts of weird things), but I would start with the CPU since you had that shorted FET in the CPU VRM already.

[atsio]

Re: I need troubleshooting assistance with provided schematic

Check all voltages on all pins of U1 and compare with working mobo. Especially the vid signals, OCSET, ICOMP and ISUM.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

I don't fully understand what you mean. Does it work in another board or do you hope it works?

You should check that the CPU is OK first, because if the CPU is dead you may be chasing a non-existent fault on the motherboard.



The fan is PWM controlled by the line FAN_CTL1 from U12, the ADT7475 fan controller chip. On this line you should see a square wave if you have a scope. If you don't have a scope, it should show a voltage probably around halfway between the chip supply voltage of 3v - IF the signal is present.

This FAN_CTL1 signal (if present from U12) needs to get to Pin 2 of U9A. Also check that the voltage at Pin 3 of U9A is OK. It should be around 3v.
If Pin 2 is at 3v as well, the opamp will set a low output, turning on Q12 and supplying power to the fan. If the fan is not going, I suspect FAN_CTL1 to be at 0v.

You need to check that signal at both sides of R165. It could be that U12 is generating the signal but it is not getting to U9A.



If the decoupling capacitors for the main voltage rails went bad, I guess it could maybe cause the problem (bad capacitors can do all sorts of weird things), but I would start with the CPU since you had that shorted FET in the CPU VRM already.

CPU works ok.
The FAN_CTL1 signal is not present at U12. At the working mobo I get about 1V.
Which capacitors do you suggest to replace?

[Agent24]

Re: I need troubleshooting assistance with provided schematic

In that case, it could be that either U12 is bad or has no supply voltage to Pin 3.

OR, what is probably more likely, the CPU is not running due to bad VCCP, and U12 is not being told to turn on with any command from the SMbus.
Without any commands from SMbus it is supposed to run the fans at full speed, but only after checking that VCCP is above 0.75v. However, in this motherboard, the VCCP detect pin of U12 is connected to GND. So it's probably in a loop waiting for VCCP to rise, or for some SMbus data. (See ADT7475 datasheet, Page 27)

Forget capacitors for now, I would advise you do what atsio says and compare the CPU VRM controller U1 pins between the working and non-working boards.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

U12 has voltage at pin 3
Also replaced it from a scrap mobo.
At U1 the main differences are at pins 20,27 & 31 that I get 1,8V instead of 2,2V.
Also pin36 I get 1,2V instead of 3,7V.
Pin5 1,08V instead of 1,29V.
At OCSET, ICOMP and ISUM [pin13, 14, 15] I get 1,22V, 1,08V & 1,08 instead of 1,42V, 1,27V & 1,28V.

[Agent24]

Re: I need troubleshooting assistance with provided schematic

What about VID signals, pins 38, 39, 40, 1, 2?

[rookieme]

Re: I need troubleshooting assistance with provided schematic

What about VID signals, pins 38, 39, 40, 1, 2?

That's strange,
at faulty one I get 1,8V at pin38 & pin1 and zero at the rest.
At working one I get 1,8V at pin39 & pin1 and zero at the rest.

[atsio]

Re: I need troubleshooting assistance with provided schematic

Are you using the same processor at both boards?

[atsio]

Re: I need troubleshooting assistance with provided schematic

Also remove and check resistance of r33

[rookieme]

Re: I need troubleshooting assistance with provided schematic

The processor is the same - I don't have a second one.
I removed R33 and it is correct [150 KOhm]

[atsio]

Re: I need troubleshooting assistance with provided schematic

First try it by replacing U1 (swap them to see if ISL works) from working board and if that doesn't work replace and ec controller.
If i were you I would replace and Q16,Q17 and Q18

[rookieme]

Re: I need troubleshooting assistance with provided schematic

I have already placed an order for U1 replacement as I don't really trust it [I'll have by the new week].
Which one is the ec controller so I can swap it?

[Agent24]

Re: I need troubleshooting assistance with provided schematic

I'm guessing the EC is U10 - what they call the "ACPI Controller"

You better hope it's not dead, because while it could just be a re-brand of a common IC, the model number on the schematic is "MS-6-RBF" and it could be a custom ASIC designed by MSI themselves. See attached 3rd party datasheet.

What does U10 have written on it?

[rookieme]

Re: I need troubleshooting assistance with provided schematic

I'm guessing the EC is U10 - what they call the "ACPI Controller"

You better hope it's not dead, because while it could just be a re-brand of a common IC, the model number on the schematic is "MS-6-RBF" and it could be a custom ASIC designed by MSI themselves. See attached 3rd party datasheet.

What does U10 have written on it?

It just writes MS-6G and a manufacture code.
I was able to find the same one at aliexpress.
So for now I'm just waiting for fresh new U1 to arrive and see the results.
If nothing happens I'll try swapping U10.
I'll have the results posted.

[Agent24]

Re: I need troubleshooting assistance with provided schematic

Good to know, searching "MS-6G" finds a lots of results I did not see before when searching for "MS6"...
Yeah try U1 first and see what happens sounds like a good plan

[atsio]

Re: I need troubleshooting assistance with provided schematic

EC controller (here called LPC) is U4 - W83627EHF. Is the only other place that the vid signals are going, and you already mentioned that you have different vid signals on each board.
Try to start both boards without processor and check vid signals again.

[rookieme]

Re: I need troubleshooting assistance with provided schematic

Without cpu I get from both about the same signals.
From pin38 to pin2 at faulty one I get 1,14V, 1,15V, 1,16V, 1,83V & 1,16V and at working one 1,20V, 1,17V, 1,17V, 1,84V & 1,17V.