Mainboard Suicide after Sleep - Page 1
Forum section: electronics / repair

author: TonyBe
author_rank: Regular Contributor
timestamp: March 26, 2020, 03:33:58 pm
content: Dear EEV-Forum,... after following Dave for years on YouTube, i finally have a reason to join you. The reason for that is that i cannot found any help elsewere - and i'm sure that there will be some expert out here who can help me out.A short story to kick things of:few days ago, I've tried to start my PC (ASRock H87 Pro4 with an Intel Xeon E3-1230V3) from sleep. Since the PC has worked for ages now, and was sleeping for just about 20min, i've expected nothing strange. But then: no graphics, a blinking Power LED (as in sleep mode), and spinning fans. Nothing else happens. So i've pushed and hold the power button to restart the PC. Since then, when i've tried to start it, it just fires the PSU for approx. 1s and even before the CPU fan can start spinning, everthing cuts off. This repeats like every 3s until i kill the power from the PSU.So i've ordered a new PSU,.. without any succes. Same problem still present. Can't even get to a BEEP or diagnostic LED, neither BIOS.After doing the generic troubleshooting (CMOS Reset, unplug battery for a while, removing all other Hardware) i've started to get very deep into the hardware and the Mainboard it self. And that is, where my questions start to come up.I found out, that the MB kills the PSU with the PS_ON Signal wire short after the PWR_GOOD comes up. I've traced the tracks on the MB-PCB to find out, that everything is controlled by a LPC I/O Chip: in this case the Nuvoton NCT6776Dhttps://media.digikey.com/pdf/Data%20Sheets/Nuvoton%20PDFs/NCT6776F,D.pdf. Studying the datasheet of this IC brings me to a new trace. On page 56 you can find a complete Logic Blockdiagram on how the PS_ON signal is generated. So I continued with probing around the chip signals to get an idea on what signal kills PS_ON output. After just a few hours i found out, that the SLP_S3# Signal was the reason for the cutof of the PSU. As you can see from the blockdiagram, there is a 32ms debouncing circuit between the signal and the AND gate,... and sure enough: when probing the PS_ON# Signal (blue Trace in image) and the SLP_S3# Signal (yellow), there is an exact delay of 32ms.Obviously the Mainboard somehow sets the PC to Sleep State 3, as soon as the PSU is ramped up all voltages.Tracing the SLP_S3# Signals over the MB shows, that this signal controls several LDO enables and power FETs of the board power circuitry and is generated by the Mainboards Chipset IC (in my case the DH82H87 S R175).Now the question: how is this possible? After removing all storage and power from the MB, how can the chipset IC still be stucked in the Sleep mode? Is this even possible without having BIOS or OS running? Is there any expert with knowledge on the processes around a PC boot out there? Is it possible to reset the Chipset IC in anyway? I'm stuck on how to continue this journey here. I'dont think that the Chip is electrically broken, since everything works with controlled and repeatable timing aso.I've already ordered a new mainboard, and really hope, that this will solve the issue and the CPU is okay.But i really want to know what is going on here - at least for the purpose of learing, i think you understand!So, all of my hope is in our your hand!Thank you in advance,Regards from GermanyTony

author: PKTKS
author_rank: Super Contributor
timestamp: March 26, 2020, 03:49:47 pm
content: Your questions are a bit vague but typical.ACPI introduced all these marvelous things youare dealing with.Basically - to be able to control the PSU and modernthermal aware CPUs/GPUs you need ACPI.ACPI uses 2 logic "hints" S3# and S5# so to controlACPI states - run / suspend / off (there are 5 states)in suspend DDRs must be powered but PSU is OFFso stdby power feeds DDR (DDR_VTT as well)to transition from suspend to ON the super I/Omust issue e generic reset to all bridges (whateverthey call North HUB .. whatever) and that will issueVRM_ON to power CPU (very simplistic)Several reasons may prevent that transitionincluding faulty regulators CPU_VRM and DDR_LDOsOther very common reason is that some Supoer I/Omostly on Notebooks contains proprietary firmwarerecorded from fabric.All that must be checkedAssuming worst case scenario changing Super I/Oafter dead sure your S3# && S5# logic is workingTedious thing - about couple hours to decide worth it or notno magic formulaBTW I have 2 boards here with similar issues.Still deciding if I will order a super I/O chip (suspected culprit)Paul

author: JKKDev
author_rank: Regular Contributor
timestamp: March 26, 2020, 03:53:35 pm
content: This one might be out there with the dumb ideas but... Did you try removing the CPU and powering on the motherboard on its own? It should start the PSU and turn on all the rails before it can even detect that the CPU is missing (or at least change the behavior which it's exhibiting now) and it should give you a signal that there is a problem with the CPU. If the behavior doesn't change then the motherboard is dead. If it changes the CPU died.

author: PKTKS
author_rank: Super Contributor
timestamp: March 26, 2020, 03:58:46 pm
content: Quote from: JKKDev on March 26, 2020, 03:53:35 pmIn that case it won't change.VRM_ON is one the latest logic signals in the chainIt won't matter if the CPU is on or off the slot.Until the S3# S5# logic properly made the transitionfrom suspend to run CPU_VRM is OFF.Usually only PCI bus is "ON" on pin 14 (if i recall correctly)powered by 3V_ALW logic - requires 5vsb to 3V LDOworking...Paul

author: LateLesley
author_rank: Frequent Contributor
timestamp: March 26, 2020, 04:08:25 pm
content: I think you are over thinking this.The way PC PSUs work, is they basically have two PSUs. One is always on when the AC is connected and supplies the +5Vsb, and then there is the main supply which is turned on when the PC signals the PSU to turn on. The +5Vsb will power this sleep circuitry and sleep mode stuff, like RAM, when in sleep mode, the main PSU does the rest.From what you describe, it sounds like as soon as you try to power the PC, the PSU is tripping out on overload protection. And it'll probably stay in that mode, until you kill the AC and then plug it back in. That usually suggests a short on a power rail somewhere.The best way to test this, would be to disconnect the PSU cables from everything, CPU M/B/ drives, the lot, then follow this instructable to jumper the PSU and test that it works.https://www.instructables.com/id/How-to-Turn-on-a-Computer-Power-Supply-Without-a-C/If that works, then you can start plugging things back in one at a time. STart with the 24 pin into the motherboard, and try the power switch. if it starts, kill the power, then ad the CPU EPS 12V, and try again, if that works, add thr GPU power if you have one, then drivers etc. If at any point it doesn't power up, that's the part that is killing it. GPU's and the CPU power can be common for killing the supply, if their VRMs short out, and it's not unheard of for other motherboard power rails to short, and kill the supply. A favourite, check the USB ports aren't damaged and shorting. Other traps with new builds, can be inexperienced folk having stand-offs under the motherboard and shorting it.If you are by all that, and troubleshooting the mainboard, you could be looking for a shorted rail.If the power stays on, but no boot - then there's several things there that could be wrong. Faulty RAM (try one stick) clear the BIOS (usually a jumper to do that) and some modern boards might turn off and on a few times before booting - they do a memory retraining thing.ANyway, hopefully that gives you a few things t check.

author: TonyBe
author_rank: Regular Contributor
timestamp: March 26, 2020, 04:38:12 pm
content: Wow that is awesome! So much valuable information after that short while. You're great! Thank you so muchAt first: removing the CPU leads to a complete dead MB... nothing happens to the peripherals (and PS_ON is also not changing when pushing the button). I've actually read about a "CPU Socket occupied" Signal, which is taken to account in the PS_ON signal statemachine of the IO Chip. So i think the chip will notice if there is no CPU and keeps the system from start. But a good hint anyway.!@Paul: this is very interessting. I'll grab the hint with the ACPI and will read about it. But as you allready described: it's a pain to decide what to do. I've checked the voltages (that i can find) as good as possible. But since the PSU gets shut down after just a few seconds, i cannot say with certainty, if the rails are good or not. I also think that it would be necessary to load the rails when measuring them, am i right? Otherwise it's not very meaningful.To clear the issue with the PSU turning off after the short period of time - would it be helpful to power it manually (short PS_ON to GND) when connected to the MB and then check the LDOs? Like the way LateLesley suggests.Thank you again for the quick and extensive help!RegardsTonyEDIT:Just one more question: if the ACPI Statemachine needs the VRM_ON Signal to get things started, would this mean that also the CPU could be damaged? I mean,.. of course,.. but: how likely is it?

author: wraper
author_rank: Unknown
timestamp: March 26, 2020, 04:48:52 pm
content: I assume you don't have a post card? IMHO it could be as simple as corrupted bios (hence it was still working before turned off) or dead CPU. Seen both cases with symptoms similar to yours.

author: TonyBe
author_rank: Regular Contributor
timestamp: March 26, 2020, 04:58:30 pm
content: No sadly i don't have one...Good that you remind me of the BIOS. Totaly forgot to told you, that i've also monitored the BIOS-Chip with the scope. Since i was able to find the datasheet for it, i probed the CS and CLK lines directly on the socket. Both are completely dead (besides they get pulled up when PSU starts). That also leads me to the point where i was kind of sure, that the BIOS isn't a thing here.Is this right? I mean: if there is no CLK, nothing tries to read or even load the BIOS from the chip, right..?Regards

author: wraper
author_rank: Unknown
timestamp: March 26, 2020, 05:13:40 pm
content: Quote from: TonyBe on March 26, 2020, 04:58:30 pmDid you use one shot trigger on oscilloscope? Since if you simply watched what's happening there, you could miss data transfer in the beginning.

author: TonyBe
author_rank: Regular Contributor
timestamp: March 26, 2020, 06:08:22 pm
content: Yes, of course. I've triggered on falling edge.. But the only snap I get, was from the voltage going down from pull-up through the slowly decharging caps.

author: TonyBe
author_rank: Regular Contributor
timestamp: March 26, 2020, 08:35:12 pm
content: Hello again,i've got an update. I was just checking for any missing voltages that i've maybee missed probing. And then i found this inductor near the Chipset IC. Next to the inductor is a LM1117 which generates 3.3V from the 5V StandBy Voltage,.. perfectly stable. As far as i can imagine (sadly i do not find any precise information on the web), another suitable voltages for the ChipsetIC should be like 1.8V or 1.2V...Since the Inductor is connected to a smal QFN8 through some passive components, i can imagine that this is a kind of a step down converter IC. When i probe the pins around the QFN or the Inductor, the only DC-Voltage i can find is around 800mV... and even this voltage is overlayed by a horrible rippel (sometimes up to 300mV,... it changes).What do you think? I might be gettin somewhere with this...See attached Image for the regulator section. The IC branding is "29 fk u1V".. Nothing to work with.EDIT:..and still, fresh news. I managed to find the Datasheet for a ChipSet from the Intel8 Series and found out, that this Supply should be at ~1V. Sometimes when the MB is off, this voltage is present,.. but if i turn on the MB, this Voltage starts to ripple a lot. Maybee this is because of the Rail getting Switched over so one of the "non-standby" rails and therefore the load for the regulator is missing... Hmm... still not 100% sure. I've unsoldered the Inductor and feed in 1V from an external Supply. It takes about 50mA,... sound quiet much for me.Regards

author: Rasz
author_rank: Super Contributor
timestamp: March 27, 2020, 01:59:18 am
content: I have very similar motherboard, same symptoms. Mine died slowly.My older posthttps://www.eevblog.com/forum/repair/what-would-cause-failure-of-4-motherboards-in-different-pc_s-within-a-few-months/msg1439544/#msg1439544:Quotethe closest you will get to ASRock H87 Pro4 motherboard diagram for free ishttps://elektrotanya.com/gigabyte_ga-z87-ds3h_rev_1.1_sch.pdf/download.htmlsadly gigabyte specific IT8620 instead of NCT6776Dalso older asrock using same LPChttps://www.scribd.com/document/426676803/AsRockbut diagram missing relevant page in free view modeIm not aware of any diagrams/boardviews for Asrock motherboardsThere are Asus/Gigabyte ones, but different LPC and cost $.For the PCH to go out of reset all the power rails (pch,cpu, dram, etc) must be present and correct to generate appropriate PWROK railsnow standby LDO getting warm is not necessary fried LDO, more likely something behind it getting shorted.Ill try to dig my board up and investigate again, its been a while.

author: wraper
author_rank: Unknown
timestamp: March 27, 2020, 02:04:05 am
content: Quote from: TonyBe on March 26, 2020, 08:35:12 pm50mA only 50mW of power, any VRM or LDO should be able to supply it easily. Have you tried running this board with external 1V supply attached? Also if you supply 1V without rest of the circuit powered, current consumption might be misleading.

author: Rasz
author_rank: Super Contributor
timestamp: March 27, 2020, 02:33:55 am
content: Quoteare we looking at different pdfs?https://media.digikey.com/pdf/Data Sheets/Nuvoton PDFs/NCT6776F,D.pdfpages 47-48 cover sleep state control including timing diagrams for power bringuppages 20-21 corresponding signals pinoutsbtw found asrock A55M-HVS diagram. asrock motherboard with NCT6776, but sadly being AMD its pretty useless to us :/https://forum.laboneinside.com/viewtopic.php?t=28Edit:another victim, ~same board, same symptomshttps://www.badcaps.net/forum/showthread.php?t=79449and another onehttps://translate.google.com/translate?hl=en&sl=ru&u=http://vlab.su/viewtopic.php%3Ff%3D244%26t%3D51260&prev=searchthis post has measurements from superIO chip, sadly from a broken board. Would be nice to have those from working onehttps://obrazki.elektroda.pl/3089055500_1561483149.pngsimilar symptomshttps://translate.google.com/translate?depth=1&hl=en&prev=search&rurl=translate.google.com&sl=ru&sp=nmt4&u=http://vlab.su/viewtopic.php%3Ff%3D244%26t%3D98796this one had broken solder joints under PCHI dont remember testing this on mine(https://translate.google.com/translate?hl=en&sl=ru&u=http://vlab.su/viewtopic.php%3Ff%3D244%26t%3D47575&prev=searchreplacing superIO fixed this onethis one died in sleep mode like yourshttps://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=search&rurl=translate.google.com&sl=ru&sp=nmt4&u=http://vlab.su/viewtopic.php%3Ff%3D244%26t%3D90365generic tutorial, not really helpful in our situationhttps://www.edaboard.com/showthread.php?161775-Step-by-step-to-repair-mainboardsomeone REverse engineered h97 low power rails:https://marcowuen.wordpress.com/2014/11/04/review-asrock-h97m-pro4-mainboard/#more-364https://marcowuen.files.wordpress.com/2014/12/h97m-pro4-circuitry1.pdf

author: TonyBe
author_rank: Regular Contributor
timestamp: March 27, 2020, 08:21:21 am
content: Very interesting news, thank you for that! Sadly my "new" MB is a Z97-C since it was the best replaycement that i could find for now... i'll see if it'll die as well. Problem being, that i always turn off the power when i'm not on my PC (like every evening, weekends, or holidays).50mW ofpPower isn't much, that is true. But as seen on the picture the only output filter caps are these tiny ceramic ones. Not sure if they're NPO/C0G,.. but given the size, whis caps are most likely just a few uF, and for a one phase regulator, that seems very low,... Anyway: i have connected my Lab Powersupply to the board by removing the big inductor. And i've monitored the current in StandyBy and start-Up conditions.@Rasz: thank you for the huge amount of links and information. I've checked the diagrams that you've send, and well. They're close to the H87, but as you mentioned not close anough to get at clear understanding on what is happening. But nice for gettin deeper in this topic anyway!Regarding the PDF.. I think i've wrote that a bit vague. I mean page 56 of the PDF Dokument, the actual sheet-number writen on the page is 36.For the DSW State Diagram: i haven't really checked this stuff, since the SLP_S3# Signal ist turned off anyway, and that corresponds directly with the PS_ON Signal going High. This SLP-S3# Signal is comming from the PCH. Do you think that the PCH switches this S3 Signal cause of LPC Commands sent by the SIO Chip?And BTW.: what does "DSW" actually stays for? Can't find a hint on google..Again: thank you all so much for the help! I wasn't able to find even a small hint and you're all giving tons of usefull stuff.Regards!EDIT: I've attached some measurements from the Output of the Regulator (shown in the microscopic picture above). Yellow is the PS_On Signal from the PSU. The Blue curve is the output which supposed to be around 1V (1.05V to be precise). First Picture shows the off condition after plugging in the PSU (StandyBy). Pic2 and Pic3 is this weird on off effect which the board is going trough after pushing the Power Button once - just with two time bases to make it clear.

author: PKTKS
author_rank: Super Contributor
timestamp: March 27, 2020, 11:55:53 am
content: Quote from: TonyBe on March 26, 2020, 04:38:12 pmHmm don't look like soFrom your report it seems you are properly makingthe transition in full... PSON goes ON and PSU triesto power the MOBO but something quickly goes weirdand the protections quick in asap.to power the CPU *ALOT* of things should happen firstwhen CPU_VRM ON goes you can at least put the Super I/Oon bottom of the suspects.I would start checking auxiliary rails mainly DDR LDOsand the auxiliary required DDR_VTT regulators.they do go bad even more frequently because if youuse suspend mode too much they just wear outPaul

author: TonyBe
author_rank: Regular Contributor
timestamp: March 27, 2020, 03:43:42 pm
content: Hi Paul,i've allready checked the VREGs around the RAM Ports. There are 3 of them in total. When the PSU ist Pluged in, the showing 0V, 0V, 500mV. When i'm trying to start the PC, the Rails are present in a clean mannor: 1.6V, 3.2V, and 5V. The only strange thing is, that the 5V rail does jump down to 2.5V when the PSU gets shot off by the SIO. Anything suspicios here?Again, the only Rail that acts weird when the PC tries to start is the 1.05V Rail from the HBC Chip. But even if i'm connecting an External Supply here, nothing changes.RegardsEDIT: Found the RT9045 VTT Regulator. It's Output voltage is around 800mV.. Seems to be okay for DDR3. I've redone the external Voltage supply test (as in picture). Something "new" happens. First of all, when the PSU in Plugged in, the 1.05V Rail is drawing around 65mA continuously. When pressing the power button, the current drops to 23mA and stays about the same. The strange thing: the MB does not try to start again without me pushing the button again. Why so? That's strange. When the inductor is in place, the boards tries to start up in an infinite loop. Now it is trying only once. What is the difference here. Hmm.

author: Rasz
author_rank: Super Contributor
timestamp: March 27, 2020, 06:39:15 pm
content: just extrapolating from what I could find:https://software.intel.com/en-us/vtune-help-s0ix-statesQuotehttps://www.anandtech.com/show/6355/intels-haswell-architecture/3Quoteafaik DSW stands for 'DeepSx Well' aka 'Deep Sleep Well' as in 'Integrated PCH Deep Sx Well (DSW) On-Die Voltage. Regulator' (3.3V to 1.05V)

author: Miti
author_rank: Super Contributor
timestamp: March 27, 2020, 09:58:29 pm
content: Did you measure the battery voltage?

author: Rasz
author_rank: Super Contributor
timestamp: March 28, 2020, 04:32:39 am
content: It does seem like PCH is not liking something.is RTC VDD present? is RTC clock running (can check using oscilloscope in high impedance mode)?with this asrock sickness often pulling battery out and resetting cmos makes the board start _once_. Mine would still start after pulling ram out for a moment, or swapping dimms aroundEdit:potentially good news, found boardviews for our boards from ~legit? looking site. No way Im giving them my CC thoand they dont accept paypal, but they do take virtual scam money (bitcoin, ethereum), minimum account charge is whole 50 roubles = $0.63enough for 5 boardviews. Sadly no diagrams.http://сервискомп-анна.рф/forums/resources/asrock-h87-pro4-rev-1-03-boardview.11254/http://сервискомп-анна.рф/forums/resources/asrock-z87-pro4-rev-1-05-boardview-fz.14324/Quoteits an Asus, isnt it? afair power problems were Asrock thingEdit2: good news everyone, boardviews in attachements.Dont bother with OpenBoardView, it crashes on those files.http://boardviewer.net/works "fine"Newer build of OpenBoardView, R7.4, works ok. Loads the boardview upside down and flipped every time, but apart from that everything is as it should be.

author: TonyBe
author_rank: Regular Contributor
timestamp: March 28, 2020, 11:46:08 am
content: The Battery Voltage is fine! I've also feed in the 3V from my external PS... no difference.And you Rasz, my friend... You are a bloody legendHow did you find this!? My god.Just give me some hours to go through this and i'll write again asap.Regards!

author: PKTKS
author_rank: Super Contributor
timestamp: March 28, 2020, 11:56:29 am
content: Quote from: TonyBe on March 27, 2020, 03:43:42 pmOCP tripped and reset required.That would lead some MLCC small cap faultyor cracked or leaking.That thing is likely spotted using an external PSUwith carefully thermal procedures...Several.. finger..() alcohol or fluid or thermal camera..Recently thermal camera render good results.But some problems are still spotted using die hard methods.MLCC is a plague.Paul

author: Rasz
author_rank: Super Contributor
timestamp: March 28, 2020, 07:39:15 pm
content: btw dude from badcaps wrote his CPU inverter starts up during this one second power loop, meaning additionally to power rails THRMTRIP might also be the culprit making the chipset decide to shut down. Gigabyte uses this signal for extra stuff like USB protection, but Asrock only connects to cpu socketnext is checking DRAM_PWROK, GR749 between bios chip and sata connectorsand try the 'press on bga chip' trick on the PCHsince your board died in the sleep you are strongly leaning into looking for sleep issues, but if you check slp_s4# you will most likely see its also triggeringPS1: PU9 you were injecting appears to be 1.05V for LAN, red herringps2: could you edit topic title to include board model 'ASRock H87 Pro4'? might be easier to spot when searching by random googlersEdit: Found something which appears to be a guide for Asus RMA technicians. 'CSC-GRMA' must of been one of ASUS contractors in ~2009-2012. Presentation for previous gen 1155 motherboards, based on p8z77-v deluxe (nuvoton NCT6776F)https://en.ppt-online.org/310961component training pdf:https://nanopdf.com/download/1-5af70798becf5_pdf

author: TonyBe
author_rank: Regular Contributor
timestamp: March 30, 2020, 04:32:46 pm
content: Hello folks,Sorry for the late reply,.. have been busy cause of the corona thing.The good news at first: my new MB (from Asus Z97c) has arrived and my PC is working like a charm.As good as this is, it's pretty hard to continue the repair, since i'm no longer having a 1150 CPU for testing the MB. I'm currently looking for a cheap CPU on eBay,.. maybe i'll buy one for test purposes.I've checked the Board Views,... they're awesome. So nice to work with it. Crazy.Thanks again for that!!Before my CPU was planted on the new MB, i've tried to push hard on the PHC, without any succes. I really want to check for the MLCC on the 1.05V Rail a0uond the PHC,.. really thinking that that is something.I'll check the guides,.. the look pretty pleasing.For editing the Topic.. is this even possible? I only found the rename function when i change the Forum,.. but that's not what i want.Regards!Tony

author: dicky96
author_rank: Regular Contributor
timestamp: March 30, 2020, 05:37:24 pm
content: Hi guys I may as well join the party hereI'm the 'dude from badcaps' that Rasz mentioned who has been looking at the same problem. My board has been sitting on one side but in light of all the information here i will have another look at itMine is the Z87 Extreme 4Boardview is here

author: TonyBe
author_rank: Regular Contributor
timestamp: March 31, 2020, 07:21:17 am
content: Quote from: dicky96 on March 30, 2020, 05:37:24 pmHi and welcome.So your Board died in wakeup from sleep as well?Regards

author: dicky96
author_rank: Regular Contributor
timestamp: March 31, 2020, 11:54:19 am
content: Actually no. Or at least I don't know.I buy motherboards and computers from the local flea market just to see if they are working or if I can repair them. I generally look for old motherboards and computers, Pentium 4 socket 478 and earlier (I've picked up some Pentium 3, Slot 1 and even 486 motherboards) and the occasional rare things like a Core 2 Quad/Extreme board with both AGP and PCI-e. I also buy old GPUs.Other than that I buy any gaming motherboards or recent boards. What I don't bother with is stuff like Dell, HP, Compaq et al and Core 2 Duo/|Pentium D which are everywhere.I fix this stuff in my spare time when I have no paying jobs in the workshop. What I fix, or was already working anyway, I either sell on ebay to buy more retro PC stuff for myself, or keep for upgrading my own retro rigs of which I have several now.This motherboard came from the flea market so I don't know it's history. It does have the same symptoms though, powering on/off every few seconds. it does the same if the ATX is forced on but at a higher cycle rate. To save repeating all the info you can find it herehttps://www.badcaps.net/forum/showthread.php?t=79449

author: dicky96
author_rank: Regular Contributor
timestamp: March 31, 2020, 02:57:32 pm
content: I had another look at my boardI have the same signal SLP_S3# going high low pin 64 on SIO. On my board this signal only connects to the PCH/North Bridge and a the gate of a FET (AQ3) that looks like it connects into the audio circuit and from the signal name on one on the centre pin DEPOP_CON I think it is meant to stop the speakers popping at power on.Here is the datasheet for my Z87 PCH. I tried removing the heatsink and applying pressure to the BGA but no difference.https://www.intel.com/content/www/us/en/products/docs/chipsets/8-series-chipset-pch-datasheet.htmlHas anyone tried lifting pin 64 of the SIO (which is conveniently situated in a corner ) and using a pull up resistor to drive it to 3.3V to see what happens? That would be my next thought when i am a tthe workshop again tomorrowRich

author: dicky96
author_rank: Regular Contributor
timestamp: March 31, 2020, 04:41:35 pm
content: I'm also thinking this could be a SIO related problem or something entirely different. As it affects different chipsets (Z87, Z97 at least) it seems a bit odd both chipsets would have the same problem and also wouldn't we be finding the same fault on motherboards from other manufacturers that use those intel chipsets? So probably we should be looking for some common factor.Firstly, do all the affected boards have the same SIO? Maybe the PCH is detecting something that it thinks represents a fault but don't you think it is odd that it would signal that fault to the SIO using SLP_S3# ?Also some of the things I tried on the badcaps thread. Forcing the ATX PSU on does not stop the on-off-on cycling of Vcore but it does increase the frequency of the cycle. Removing the BIOS makes no difference so it's not like the CPU is signalling the reset.On the north bridge the 3.3V and 1.1V supplies are cycling on and off. It seems to me that shortly after the 1.1V Supply to the PCH comes up, it sets SLP_S3# low which powers down the PSU, thus removing 1.1V supply from the PCH so SLP_S3# goes high again and the PSU powers back up.Forcing SLP_S3# high by lifting pin 64 of SIO has got to be the next thing to try. If that doesn't cause the power cycling to stop (of if it stops the cycling but the board still won't boot so possibly the timing of SLP_S3# going high is important) I'm inclined to lash together a simple latch circuit on breadboard, trigger it from thepadof SIO 64 going high and use it to latchpin64 high. The aim of this would be to determine if the motherboard can boot, i.e. the hardware is actually good. If it can, then it seems the PCH is detecting a phantom fault. This doesn't' fix it but it could be a useful insightRich

author: TonyBe
author_rank: Regular Contributor
timestamp: March 31, 2020, 07:19:45 pm
content: Hi,well, that's great dicky. Really appreciate your work.Good to know, that they are guys out there like you (especially when the 96 is your year of birth ^.^)Back to Topic: i've allready used a scalpel to cut a trace very close to the PCH since on my board, several transistors for voltage regulators are switched by the Signal, so i really need to make sure, that only the PCH is deconnected.I then soldered a thin wire to pin 64 and feed in a 3V3 Signal so simulate a "healthy" SLP_S3#. When pressing the power switch, the on-off symptom does no longer apear. The PSU stays on, the CPU Fan starts spinning slowly and keeps a low speed. But nothing else happens. No CLK Signal @ BIOS Flash. Therefore, i think, that the HBC or the SIO Chip still prevents the MB to properly start booting. Reason being (possibly), that SLP_S5# is also faulty..? never checked that sadly.I like the idea of finding an common fault... but at the moment, i'm having this issue with the 1.05V Rail at the HBC... and if i cannot find a faulty Cap or something like that, the fault must be inside the HBC. And if this is the case, i'm no longer able to fix the board since the HBC-Chip isn't available or even if so, would be so expensive, that it would not make any sense to spend the money in suspect only.I'm still stuck on a missing 1150 CPU for further repair work.. but i'm trying to find a common point of all the observations, which clears the possible fault. If there is a bad MLCC on the 1.05V Rail, why should it only clip the DC/DC regulator and not the external Lab Supply,... when feeding externaly, the voltage is stable, so even if there is a faulty cap, it should at least boot up with a higher current on that rail,.. so hm... i'm not quiet sure. :/RegardsTony

author: dicky96
author_rank: Regular Contributor
timestamp: March 31, 2020, 08:28:06 pm
content: OK that's also interesting to hear you tried that.I may go ahead with my idea to lash up a latch circuit on that pin tomorrow and see what, if anything, occurs96 is not my birth year by the way, it comes from an email address i set up back in the day many moons ago and somebody else already had dicky69......Unfortunately that isn't my birth year either lolRich

author: Rasz
author_rank: Super Contributor
timestamp: April 01, 2020, 02:23:55 am
content: Quote from: TonyBe on March 31, 2020, 07:19:45 pmare you still talking about PU9? this is standby supply, powers lan controller and pch in deep sleepin S0 1.05v is generated from ram power supply (PU3) in linear fashion using power mosfet Q33 (AP9T16) and LM324 as a regulatorfor 1.05 to work:ram supply must be ok - DRAM_PWROK, GR749 between bios chip and sata connectorsLM324 regulation must be ok - 1.05V on Q33Im in same boat, no spare cpu to test my broken board while in quarantine

author: dicky96
author_rank: Regular Contributor
timestamp: April 01, 2020, 11:50:15 am
content: OK so I spent some more time on thisI lifted pin 64 of the SIO and soldered a 470R resistor to the pin but unfortunately while I was trying to attach the other end of the resistor to 3.3V I broke the pin off the SIO. Shpould have done the soldering the other way round lol.Not to be deterred I tried it anyway and find the PSU powers up and stays on. I now have 1.1V and 3V to the PCH and Vcore to the CPU. PSON# is low so I can only assume the broken pin on the SIO is floating high.However I have no POST. My POST test card says FFFF or some other random reading which generally suggests to me that the CPU is not running at allI referred to the datasheet for the Z87 PCH and traced out some signals. PWROK is good so the PCH is obviously happy that all voltage rails are up. It's 3V on the PCH and it drops to 1V on the other side of resistor R8614 which signals Power OK to the CPUBut PLTRST# and PLTRST_PROC# are low. On my board PLTRST# goes to a vacant resistor space which should connect the signal to the SIO and doesn't seem to go anywhere else and as the resistor is not present and I can't see any signs of damage or soldering I assume this signal is not used. But PLTRST_PROC# is asserted so the CPU never gets out of reset.Right now I need to order a replacement SIO NCT6776D and I think a PCH as well. Both are available on aliexpress with good reviews from other buyers and total costs about 20 euros for the two. I will order today but given the lockdown, Correos (Spanish post) is rather slow here right now. I did get a delivery form the UK yesterday so obviously they are working to some extent.The only other thing I can think to try is to lift one of the resistors between PCH and CPU and connect PLTRST_PROC# to PCH 1V supply via a resistor - to see what happens....Rich

author: Rasz
author_rank: Super Contributor
timestamp: April 02, 2020, 04:52:56 am
content: Quote from: dicky96 on April 01, 2020, 11:50:15 amgood forstandby onlystarting the boot processQuote from: dicky96 on April 01, 2020, 11:50:15 amhow about RP63 PWM_PG on boardview, SYS_PWROK W31 in intel datasheets?reset wont go up without it

author: TonyBe
author_rank: Regular Contributor
timestamp: April 03, 2020, 07:23:20 am
content: Hi guys,well that's interesting. I really wonder if the RST issue is the same on my board, since the PSU stays on as well, when feeding the SLP_S3# signal externaly. Have you probed the SLP_S5# signal as well? Would be interesting to see if the PHC does send out this signal in a proper fashion or if it signals "power off" as well.With the change of SIO and PHC, things getting really exciting right now.That way we'll know if the issue is caused by a faulty IC or a peripheral,... at least dickys issue. I'M definetly stay tuned for that updateThanks guys, has been such a valuable discussion.. even till here!Regards

author: dicky96
author_rank: Regular Contributor
timestamp: April 03, 2020, 12:28:00 pm
content: @RASzOn my board RP63 PWM_PG on boardview (SYS_PWROK W31 in intel datasheets) does not connect to anywhere else apart from the pin on the PCH according to the boardview, so I can't probe it and would have to assume it is unused@TonyBeSame applies with SLP_S5# signal. it does not go anywhere according to the board view so again seems to be unused.I put the board back on the bench today and Vcore is going on-off-on where as I swear the other day it was permanently on at about 1.7V The only thing I did was to put the heatsink back on the PCH before I put the board on one side waiting parts, but taking it back off today made no difference. I could be wrong about vcore being on yesterday. 3.3V and 1.1V to the PCH are both on (measured on the capacitors mounted on the BGA substrate.TonyBe - what do you have on Vcore when you force SLP_S3# high, and do you have 3.3V and 1.1V to the PCH?It will be some time for the PCH and SIO to arrive from Aliexpress :-( We are 3 weeks into our lockdown tomorrow, with at least 9 more days to go after that and the postal service here seems to be not functioning.

author: TonyBe
author_rank: Regular Contributor
timestamp: April 04, 2020, 09:36:49 am
content: Hello again,this Lock-Down really start's getting harder and harder,... hopefully everthing will be over soon.Regarding the voltages:i'm not sure if I can measure those voltages when no CPU is loaded in. I can turn on the PSU manually but since all of those regulators seems to have EN Logic, i'm not sure if the results are valid.But what i've measured before the CPU was plug on the new MB: the 3.3V were there and also quiet clean. The 1.1V (or in my case 1.05V) were very messy, as described above... But: I'm not sure how the switching between the voltage Rails is done when the MB starts to boot. Maybee those weird ripple effects were due to bad loading condition when the StandyBy Rails are "floating".I'm still looking for a good 1150 Socket CPU which I can buy for further use (if the MB Repaiur should be succesful).Regards

author: Rasz
author_rank: Super Contributor
timestamp: April 04, 2020, 10:25:20 am
content: Quote from: dicky96 on April 03, 2020, 12:28:00 pmyou can probe it on the resistor marked RP63, its used toenable CPU Vcoresense Vcore PGOOD signal directly from ISL6379Quote from: dicky96 on April 03, 2020, 12:28:00 pmPCH uses SLP_S4# insteadQuote from: dicky96 on April 03, 2020, 12:28:00 pmPCH detecting problem with Vcore and cutting power?

author: dicky96
author_rank: Regular Contributor
timestamp: April 05, 2020, 11:39:36 am
content: I had forgotten Tony doesn't have a CPU for his motherboard. Mine will not turn on at all without a CPU.I'll have a look tomorrow to see what is going on with the Vcore, I should be able to determine what signal is causing it to switch on and offRich

author: dicky96
author_rank: Regular Contributor
timestamp: April 08, 2020, 01:46:06 pm
content: OK, I've been doing another few jobs but I have come back to look at this againThe VRM controller for Vcore is an ISL6379. I can see various signals flicking on and off (VCORE EN, VC RDY) as I would expect as Vcore is also doing that too - but nothing seems easy in this world as I couldn't find a datasheet for ISL6379.Without that it is hard to determine which signal is dependant on which other ones being present first. In other words is the Vcore being switched on and off by another chip (PCH?)or is the 6379 detecting an error when it does power up Vcore and shutting back down againI don't suppose anyone could find a datasheet for this chip?Rich

author: Rasz
author_rank: Super Contributor
timestamp: April 09, 2020, 03:55:15 am
content: solder wires to both and put scope/LA probes on them, the second one should never go out on its ownQuoteclosehttps://xdevs.com/doc/_Datasheets/_DC_DC/isl6366.pdfwould be sad if it turns out to be CPU power section problem

author: dicky96
author_rank: Regular Contributor
timestamp: April 09, 2020, 12:19:40 pm
content: Hi RaszI had another look. Unfortunately the datasheet you gave me is not similar to my chip I think - the pin outs are all different for a start, looking at the board viewI have VCORE_EN pin 3 of ISL6379 going on and offVcore is going on and off and looking at all the ISEN+/- they are all going on and off as well and all seem to be behaving identically (same voltages during the brief on phase)I can't get my head around how that happens, or what is going on with dual mosfet QT19 - 2N7002BKS. VCORE_EN connects to pin 6 of QT19, but pin 5 is high 3.3V constant and all the other pins are 0V. If VCORE_EN is supposed to be an input why isn't it shown connecting to anywhere else because it can't be controlled via QT19 unless I am losing my head lol? Could you look at the boardview for the Z87 Extreme4 and the 2N7002BKS datasheet and see if you can figure out how this is supposed to work?However that is just for my own interest, as there is something wrong with Phase 1 of Vcore on my board!. The waveform on the MOSFET gate looks different from all the other phases and so does the output to the inductor. If I can find someway to balance my phone in front of my scope I will record some videoRichHowever, at the moment

author: TonyBe
author_rank: Regular Contributor
timestamp: April 09, 2020, 02:18:31 pm
content: Quote from: dicky96 on April 09, 2020, 12:19:40 pmHi, i'm back for some more guessingi've checked the Board View from Z87EX4.. When highlighting the VCORE_EN Signal, I can see that this signal connects to QT19, the ISL and several more Caps and also (!) resistors. Since i expect the input impedances from QT19 and the ISL to be very high, i really think that the signal comes from the resistors.Further: Resistor RP839 is a 12k one pulling the Signal to GND. RP837 Pulls the Signal to ATX+12V. Since this is an 100k resistor, the 12V will be devided to around 1.18V which fits the logic levels quiet well.So my gues here is, that VCORE_EN is naturaly pulled HIGH and gets switched LOW by one of the transistors. Checking the datasheet of QT19, this seems to be confirmed. Pin 6 of QT19 is the drain of a n-channel FET. Since pin 2 is the gate of the transistor, this pin is the one you really interested in. Checking this pin, you'll see, that it connects to pin 3 (the drain of the second package FET) and to a +12V pull-up resistor. This seems to form a simple FET inverter circuit.And well,... now i understand why you just checked pin 5*fail*The point is, i can only think of QT19 to switch the EN-Signal. Since Pin5 is High, the Transistor should not ground the EN voltage, and therefore, the EN should be high. Have you tried to lift Pin 6 of the SOT-363? If the Transistor is dead, the enable signal could be tight to ground, resulting in no enable for the ISL...?Really fun to check all this stuff.See my reconstructed schematic attached. I start thinking, that this logic is working and all that you see is the on/off of the 12V ATX Voltage which results in the Pull-Up resistors have nothing to pull against.Regards

author: dicky96
author_rank: Regular Contributor
timestamp: April 09, 2020, 05:11:26 pm
content: Looking at that diagram it seems to me that OTE_GATE1 going high would ground the gate of QT19A causing VCORE_EN to go to whatever is the voltage on the junction of the 100K/12K resistors - which quick mental arithmatic says is gonna be near to 1.2VOTP_GATE1 going low would connect VCORE_EN to whatever voltage is on OTP_EN, basically. As QT19A is effectively in parallel with the 1.2K resistor that voltage is going to be something less that 1.2VIf i remember correctly from this morning VCORE_EN was indeed switching between about 1.2V and 0V. But all the other pins of QT19 were static as I posted earlierI definintely have something wrong with Vcore phase 1 so I am going to concentrate on that tomorrow. At first it looked from the boardview that PWM 1 - 6 from the ISL6379 go nowhere, which does not make sense, until I clicked on the Net names and found they go to six ISL6625ACRZ mosfet drivers on the other side of the PCB. I will have a look at that area. I suspect that the output mosfets of Vcore phase 1 are getting no high side (and maybe low side) gate drive.I can imagine how that may cause the ISL6379 PWM controller to have a hissy fit and repeatedly shut down Vcore

author: TonyBe
author_rank: Regular Contributor
timestamp: April 10, 2020, 09:14:11 am
content: HiQuote from: dicky96 on April 09, 2020, 05:11:26 pmYes, that fit's my opinion about the circuit quiet well. The only thing i would add is that OTP_EN is more likely another "Flag" to controll VCORE. It's like a weird "AND" circuit for turnung off VCORE_EN since both, OTE and OTP needs to have a specific state to make VCORE_EN=LOW.Anyway: I have good news about my MB..Instead of buying a CPU, i've just figured out, how the CPU_OCCUPIED signal is put together by the MB and add a single Jumper to let the SIO believe in the presence of a CPU. ^.^I then connected the PSU, pushed the Powerbutton and yes, indeed: the MB cycles through PSU on/off sequence as before.Reason for that quick fix was a new assumption that i was burning for to check. With the boardview files in hand, i found the datasheet for the DC/DC regulator (RT8065ZQW) which was connected to the inductor i've desoldered (mentioned earlier, see pictures). As described above, feeding the 1.05V externally has not made a change for me back then. But since i'ce never had a datasheet for the regulator, i couldn't check for any powergood signals or similar.Well indeed: with my Lab PowerSupply turned to 1.05V, the PowerGood of the RT8065ZQW gives out 0V. I litterally turned the Lab Supply a tiny tiny bit higher to 1.08V to get this Signal coming up to 3.3V.Reconnecting everthing together, pushing the Powerbutton and there we go... a constantly spinning PSU Fan and healthy SLP# Signals.Now i'm really heading for a new CPU to try this puppy...Still don't know what really causes this 1.05V Rail to getting loaded to that heavy ripple. Could be the DC/DC Regulator, or a faulty Cap... don't know. The current consumption really jumps up and down quiet heavily.RegardsEDIT: just found out, that i can sample this part.. so i'll do this and then replace it.Let's see if this works.

author: dicky96
author_rank: Regular Contributor
timestamp: April 10, 2020, 10:13:33 am
content: Well done TonyI think my bord may have a different problem to yours as on mine there is no voltage regulator getting hot in that area.It is possible that I have another pin with an active signal on QT18, and maybe I just didn't get a good connection with my scope probe and thought I had 0V. I will check again out of interest. It doesn't make much sense otherwise.I'm fairly convinced now, that I have a VCore VRM Problem, Phase 1.I would have done more on this today but the battery on my Van has given up the ghost. It's been acting up for the last week, not charging properly. I had it on a trickle charger on Monday night, and it was OK for 2 days but yesterday I didn't have enough power to start the van again, I had to bump start it. So I trickle charged the battery again for 18 hours but this morning it still doesn't have enough power to start. Of course it is Good Friday, plus all the shops here are closed anyway apart from food and chemists, due to the lock down. So the only way to get a battery is to email or message one of the car parts shops, who then get back to you and give you a time to go and collect it. So no chance to get a battery or go to the workshop today. Probably they will be closed until Monday (we have Thursday Friday Easter holidays here)

author: TonyBe
author_rank: Regular Contributor
timestamp: April 10, 2020, 12:36:12 pm
content: Thank you, would never found that problem withour your help guys, so shout out to you!Well that's a classic murphy isn't itHope you'll find a replacement very soon. I'll stay tuned to this thread so no worries.Have a great time (as far this is possible at the moment)Regards

author: dicky96
author_rank: Regular Contributor
timestamp: April 13, 2020, 12:27:21 pm
content: OK so I got my van back on the road. The shop was closed to the public but they offer a delivery service instead.I had a look at the motherboard, the MosFETS are marked K03J4 3G2 62D1 lhigh side and K03J5 3C5 60G1 low side.The MosFET drivers are ISL6625ACRZLooking at Phase 1, it has a longer burst of PWM pulses from the controller ISL6379CRZ than the other phases, then the Vcore shuts off. The other phases all look identicalChecking the ISL6625ACRZ on phase 1, I have high side gate drive but no low side gate drive (actually I do have some low side gate drive but it is very much attenuated compared with the other phases)Also the waveform on pin 8 ISL6625 (Phase) looks horrible compared to the othersI measured the DC resistance from the Ugate and LGate phase 1 and they read the same as form the gates of the other phases.So it looks like I have a defective ISL6625ACRZ on phase 1, with no low side gate drive. But it could be defective FETs I guess though I can't see any difference on the diode range of my multimeter when compared to the other phasesI can get the ISL6625ACRZ cheap enough, and also the ISL6379CRZ is not expensive if I want to order that as well. However i can't find any MosFETs with those numbers... does anyone know what they are?I suppose I could swap the MosFETS from phase 1 to another phase to eliminate themRich

author: PKTKS
author_rank: Super Contributor
timestamp: April 14, 2020, 11:04:56 am
content: MOSFETs (compared to other ICs) are much more easy to replaceYou need to find a "compatible" or even "superior" one withthe original proper specifications.ICs are not that kind to replace.Paul

author: TonyBe
author_rank: Regular Contributor
timestamp: April 14, 2020, 12:46:16 pm
content: Quote from: dicky96 on April 13, 2020, 12:27:21 pmHi Dicky,i'm not sure if i'm getting your question right, but the FETs at the Phase-Inductors are completely identified in the Boardview file... You've mentioned"K03J4 3G2 62D1" and "K03J5 3C5 60G1". That fits the Boardview Information quiet well:- N-MOSFET RJK03J4DPA WPAK(3) RENESAS/30V/4.6MOHM- N-MOSFET RJK03J5DPA WPAK(3) RENESAS/30V/7.2MOHMBut even with that ID, i wasn't able to find a datasheet for that. So i've checked the naming conventions from renesas on their webpage and find out, that the "J" in "03J4" is kind of weird. They used to place a "0" there. So i've replaced the search term with RJK0304DP and there you'll find some information.Here you go with at least one Datasheethttps://www.renesas.com/us/en/doc/products/transistor/003/rej03g1352_rjk0304dpbds.pdf. This Part matches the mini discription of boardview quiet well.Maybee this helps you a little further my friendI've received my DCDC replacement IC few minutes ago, but of course: murphy hits me hard. The heating element of my hot air rework station has blown up yesterday... so one more week for getting new rework station. Hm.I'll post an update if i'm done replacing the regulator.Regards!

author: dicky96
author_rank: Regular Contributor
timestamp: April 14, 2020, 06:05:24 pm
content: Quote from: TonyBe on April 14, 2020, 12:46:16 pmDamn I should have thought to look there lol. Now I can find them on AliexpressI've already ordered some of the ISL6625ACRZ as I think that is what is playing up here. I may as well get a few FETs as I can get a pack of 5 for less that 3 euros and it's good to keep parts in stock.Cheers

author: TonyBe
author_rank: Regular Contributor
timestamp: April 17, 2020, 03:06:28 pm
content: NiceHappy to was able to help you.I got some good news today. I managed to get my reworkstation back to life, changed the DCDC Chip that I discovered to be faulty.And well: the MB stays on when powering on. Since i've no CPU to test with, i'm not 100% sure if everthing is working. But I think the chances are good, since this was the only issue.Yet again: thank you all!Dicky: i'll stay tuned for your issue.RegardsTony

author: koincidencia
author_rank: Newbie
timestamp: January 28, 2021, 03:46:44 pm
content: Hello everyone,I have an Asrock Z87M Extreme4 MB. We had a power outage and after that, the PC was not able to turn on, it was continuously resetting in a similar way as TonyBe described. It was confusing, because without memory, if I left the system with an unplugged power supply for 2+ minutes, then after the first power-up I got 3 long beeps (indicating missing RAM), but if I have reset the system it was going back to this reset loop.Based on this forum thread I could identify that the same DCDC converter IC is bad. I have fed 1.05V to the south-bridge rail and I was able to get into the BIOS. I am waiting for RT8065ZQW chips, hopefully replacing them will fix my issue as well.I am just writing this message to thank all of you for writing about your experience and debugging, which helped me a lot!

author: wlundall
author_rank: Newbie
timestamp: June 20, 2021, 01:01:00 am
content: Re NCT6776D :Hey Guys.. Is it any way possible to replace this chip.. i have a ASAROCK z97 extrem 4 and seems like my chip died. can see it is burntCould i simply buy a chip and re Z9solder it any help would be appreciatedKeep Well be safeThanks To any one who reeds this

author: LateLesley
author_rank: Frequent Contributor
timestamp: June 20, 2021, 02:39:19 am
content: Quote from: wlundall on June 20, 2021, 01:01:00 amWith the right tools, yes. But there may be more you'd have to do. The chips don't burn up for no reason, so before you replace the chip, you should get the datasheet, take off the old chip, then test all the powerlines first. It's probably not blown for no reason, so it's important you check out what caused it to pop.That chip is what they call the Super IO chip, it does your keyboard interface, voltage monitoring, fan control etc. It's a multi-function chip.https://www.nuvoton.com/products/cloud-computing/i-o/super-i-o-series/nct6776d/To replace it, you'll probably need a hot air station, and soldering iron, and some decent flux. If you are in a pinch though, I have seen chips removed using a GU10 50W light bulb.It's a hacky way to do it, but can be used if you are REALLY stuck. Hot air station is the best way.You'll also need a multimeter with decent probes, so you can test the powerlines with the chip off the board. Which may take some doing, as I think it needs that chip to power some stuff on. :-) You might be jumpering things out to test them.But do try and figure out what caused it to burn up. Look for shorted caps, or regulators (LDOs) that have failed. Because if you don't find what popped it in the first place, it may just burn up a new chip.I wish you luck in your repair adventures. :-)

author: barb
author_rank: Newbie
timestamp: February 14, 2022, 09:35:35 am
content: Quote from: TonyBe on April 10, 2020, 09:14:11 amI made an account just to reply to this message: I have an Asrock b75m DGS r2 that power cycled just like yours. I stabbed the feedback, P_GOOD and output pins of the 1.05V regulator with the scope: output comes on briefly at about 1.04V, but P_GOOD is latched to GND! I was able to desolder the inductor, thus severing the connection between the regulator and PCH, then I used a small buck converter set to 1.1V, wired it up to 3.3V and connected the output where the inductor would have been and guess what? The board posted JUST FINE!!!I then found a suitable 3.3VSB pad conveniently located near the VRM and wired it to my external regulator, this way I was able to re-gain sleep functionality as well.Mad props to you for figuring this out, I'll look further into tidier repair options, but with the board working fine ATM I'm not too inclined in risking it. It's an old board anyway and I just want to squeeze 1-2 years out of it