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Troubleshooting Gigabyte Z390 Designare Motherboard

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    Troubleshooting Gigabyte Z390 Designare Motherboard

    Hello, I am starting to get into board level repairs and diagnosis with primarily desktop motherboards, I've got a lot of them lying around.
    This one in particular is a Gigabyte Z390 Designare. Standby voltages are present, with CPU and RAM installed the board will power on, fail to POST with the debug light stuck on CPU then the board will continue reboot and attempt POST repeatedly. CPU is cold, chipset gets slightly warm. 5V is present at the CPU MOSFETs but the PWM appears to not be sending the signal to send the power through to VCORE, getting 0V on all inductors. The PWM is an ISL69138 and it seems the only way to get a real datasheet on it is to ask Renesas pretty pretty please. The same goes for the super IO which is an IT8688E as it seems ITE doesn't like to share either so I can't determine how to check if anything is trying to talk to the PWM.
    This appears to be a very common failure on desktop motherboards as I have several others with the same problem of various chipsets and manufacturers, including Z690 boards already.
    As I said, I am new to board level diagnosis so I would ask to those with experience:
    What is a good procedure that you like to follow when dealing with the diagnosis of these machines?
    What are the common components to fail on desktop motherboards?
    Before you ask, yes the CPU and RAM are both known working, they're a Celeron G4930 and Corsair LPX 3200MHz that I use for all Z390 chipset motherboards, and there is no obvious physical damage to either components or the PCB.
    Any input is appreciated, I'm really just trying to learn more about how the systems work, cheers!

    #2
    Re: Troubleshooting Gigabyte Z390 Designare Motherboard

    welcome onboard motherboard repair.....
    first you must know the motherboard voltage rises in sequence, you must know the sequence... as you said CPU is cold, so likely CPU_VTT voltage did not arise due to pwm chip not function, in which you had to find out why..
    there are quite afew conditions for it to fulfill first before the pwm chip works..
    you can check VCC SA, VCCIO etc ... you need a board view and and sequence flow chart

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