Asus Z97-a power cycle, no boot no cpu voltage

[meraklinetx]

Hello, I have an asus Z97-A motherboard and it doesn't start which was working properly before, the problem isn't related by ram, ram slots or psu (I changed all and nothing work), the exact problem is when you switch it on , it starts and after 1 seconds (no boot or display picture) it's off and then on cycle continuously until you power it off from psu also it's responding to the power switch for turning it off if you keep pressing it 3 or 4 seconds (power button pin has 3.3v) , also when you start it with eatx 12v socket connected this is happening (power cycle also all voltages are resetting everytime like 12v, 5v and 3.3v ) and vcore voltage is producing up tu 1.1v then goes to 0v and this keeps like that during power cycle, also the cpu power (red led light is not coming up) isn't working, but if you try to power it on without 12v eatx cpu power cable, system is getting power and doesn't enter the power cycle and all voltages are stays OK (12v,5v and 3.3v) but if you attach 12v cpu power it's entering the power cycle, also all cpu pins are OK, no bend, cpu is also OK, and there is no short circuit on 12v cpu power line.

However if I force to power on motherboard with all power cables attached (atx 24 pin + eatx 12v cpu) by sorting green and black cable on psu, it doesn't enter the power cycle loops but cpu vcore voltages is not producing also system doesn't boot again (no display) but nothing is also not getting even warm (i mean no symptoms of short circuit)

So guys help me , what to do ?? And what might be the problem?? Can it be an damaged bios firmware?? Or some other issue??

Ps. I have bordview diagram for this board and inspected the 12v cpu power phase line but everything seems to normal, I am unable to find the problem

Can it be an currapted bios or bad pch chip?

[meraklinetx]

Re: ASUS Z97-A restart loop

Hello, any updated solution for this. I have the same problem, same mainboard, when the additional CPU power supply 12v is connected, the board restarts every 2 seconds. Each coil leaks 1.5v at those times. I didn't notice a short circuit. Tried with different CPU, memory and power supply, all the same. Tried another BIOS. Has anyone had this problem or any ideas? Thanks in advance

I have just exactly the same situation, did you find and solution?? Did you fixed this?? And what is the problem?

[meraklinetx]

Re: ASUS Z97-A restart loop

Any news??

[meraklinetx]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Any idea ?? , comon.. no body don't have any idea ??

[anikin73]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Likely certain voltage did not appear...this gen motherboard has a common issue , pch 1.05v not present. U can try measuring that

[anikin73]

Re: ASUS Z97-A restart loop

Boot looping likely is certain voltage did not appear...hence boot loop

[meraklinetx]

Re: ASUS Z97-A restart loop

Boot looping likely is certain voltage did not appear...hence boot loop

Yes it is, you are definitely right, cpu vcc core is missing but why ?? What is causing this ?? There is no reason that not to be exist , no short circuit mosfets on 12v cpu line also no open circuit on 12v cpu power line (tested all with an multimeter)

[CapLeaker]

Re: ASUS Z97-A restart loop

Reset the bios.

[meraklinetx]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Likely certain voltage did not appear...this gen motherboard has a common issue , pch 1.05v not present. U can try measuring that

Yes my friend, you are definitely right, the pch voltage is missing (1.05v) but the problem is about the power rail of the chipset (pl01) , I mean not the chipset faults, when I supplied to the chipset power rail 1.05v with the bench power supply, the motherboard is working as normally expected, but now the problem is why is that voltage is missing, according to the board view of the motherboard, I can't figure out what is causing the pch voltage (1.05v) not being generated, if I have service manual, I could find the reason but board view diagram is making it to be confused, but what I understand is that there is an dc - dc step-down buck converter which is called as rt8065 11 pin ic that's converting 5v to 1.05v and supplying the pch voltage rail, but due to an reason the enable signal of the chip is not triggered and pgood signal is missing on that chip so there is no 1.05v on output voltage rail to supply the pch , so , does it have any schematic diagram of the mainboard?? If found then , I may find that why the enabled pin of the rt8065 chip is not being getting triggered

Thank you so much

[meraklinetx]

Re: ASUS Z97-A restart loop

Thanks for all replies, my issue was the pch 1.05v is missing, when the 1.05v is supplied directly to the pch power rail then, motherboard is working as normally expected, but I couldn't evaluate that why the pch voltage is missing, any ideas that why it is not being generated??

[anikin73]

Re: Asus Z97-a power cycle, no boot no cpu voltage

There is a chip that always spoilt. It has a marking 29 on it...
you need to change it.usually near pch

[ponykotze]

Re: Asus Z97-a power cycle, no boot no cpu voltage

There is a chip that always spoilt. It has a marking 29 on it...
you need to change it.usually near pch

Is that the suspicious chip you‘ve mentioned? I‘ve got the same problem with my Asus Sabertooth Z97 Mark S…

[anikin73]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Yes it is one. Output 1.05v

[Ken123]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Found what chip it is or a suitable replacement for it?

[Ken123]

Re: Asus Z97-a power cycle, no boot no cpu voltage

Could it be an rt8065 maybe?

[anikin73]

Yes it is... u can try. But some times when it fail, it kill the pch also...