ASUS MAXIMUM VIII HERO POWER ISSUE

[mo000]

HI
I HAVE NOTHERBOARD ASUS MAXIMUM VIII HERO powering on and off with cpu 8pin
NO SHORT IN VRM
cpu vcor vccsa vccio apears when motherboard powe up
vccpll missing
i check vddq for ddr4 i found it 1.1 instead off 1.2v ?
i check every coil no short .

[DynaxSC]

Check all 4 RAM voltages (0,6V, 1.2V, 2.5V and 3.3V which sometimes is also a second separate 2,5V), mostly 0,6V is missing due to buck controller failure. 1.1V is strange, should be 1.2V, higher if XMP is on. 0,6V is usually generated from 1.2V, so low 1.2V might be result of too high load (failure) from the 0,6V buck controller.
Look not only for shorts, but also for buck controllers generating no voltage but having its ENABLE pin ON. Not always there are shorts, sometime just the controller is gone w/o short.

[mo000]

Check all 4 RAM voltages (0,6V, 1.2V, 2.5V and 3.3V which sometimes is also a second separate 2,5V), mostly 0,6V is missing due to buck controller failure. 1.1V is strange, should be 1.2V, higher if XMP is on. 0,6V is usually generated from 1.2V, so low 1.2V might be result of too high load (failure) from the 0,6V buck controller.
Look not only for shorts, but also for buck controllers generating no voltage but having its ENABLE pin ON. Not always there are shorts, sometime just the controller is gone w/o short.

you mean ddr vtt ?
but what is the relation ? even ddr vtt is missing but the motherboard should power with cpu
i think ram circuit works fine becase yesterday the motherboard suddenly powered with display and vddq becomes 1.2
i think somthing related to cpu because when test motherboard without cpu 8pin vddq becomes 1.0 v

[DynaxSC]

Yes, I mean ddr vtt, without it power sequence can't be completed and CPU can't execute any order related to RAM contents as RAM does not work, so it can't even start POST. If even one voltage is missing you will get this repeating power on/off you have. This is a very typical bahavior of mobos, when some powerline is not rising in the power sequence. If not all powers will rise in a certain time and order, the board resets and tries once again to power up all powers from the beginning in an endless loop. Some boards also stop and just power off if power sequence was not succesful.
Another reason can be just ripped off or faulty smd elements in the power sequence logic, but this is less probable.