Asus Z170 Pro Gaming - doesnt power cycle

[Pedro Alves]

I have Asus Z170 Pro Gaming motherboard, it's working fine apart from the reset and shutdown commands. It doesn't restart when exit the bios or choose to restart in the operating system. Shut down also doesn't work, everything works normally until the moment it should turn off. The only way to turn off is by keep pressing power button for a few seconds. What could it be? This would be my first motherboard repair

[DynaxSC]

I would suspect some CPU pins not contacting well, had similar bahaviour on another board after replacing CPU socket, where some pin had not soldered correctly, never found out which signal this was. After second replacement of the socket the strange bahaviour went away. Examine pin alignment in the CPU socket and clean the cpu pads, and if you feel beeing slick with your hands, clean the cpu pins with a small fine brush and isopropyl alcohol (99,9% clean). Guide the brush only in direction of the pins, never against. Dry the alcohol in the socket with pressurized air, if you not have with hotair gun at ca 200 C.

Other reason could be demaged BIOS or Windows installation. Try reflash BIOS, or better would be to backup the BIOS and program a stock BIOS for checking if the issue will go away. If not revert to the BIOS backup. Try a fresh Windows installation or a Linux installation to check if this is OS related.

Could be also a missing or demaged Management Engine (ME = chipset firmware). Try to install a new ME under Windows, ASUS should have some tool available on the support site, or u can use also Intel CSME tools.

Finally could be some issue with SIO or chipset (partially demaged) or missing parts / scratches / broken tracks, shorted caps, ....etc., on the board.

U may also check indirectly with Windows event viewer if there are any issues with devices on the board. Demaged, unresponsive chips (eg. audio, LAN, usb, ...) might block/disturb normal Windows operation.

[Pedro Alves]

DynaxSC Thank you for your reply.

I've tried fresh windows install and also flashing the bios. Don't think it's OS related, since even when I go for save and exit biot the PC doesn't restart.

I will try cleaning the CPU and the socket as you suggested.

I've inspected the board and couldn't find any fault, but I don't have any experience in board diagnosing. I did find the boardview file for this board on this forum and traced the reset switch to the SUPER IO NCT6793D LQFP-128//NUVOTON chip and the caps along the way.

A bit off topic, I've tried to remove some mosfets from a dead 980ti with my cheap air 858d hot air station and it seemed impossible, solder would never melt, guess I also need a way to pre heat the whole board first. So if I want to replace the SIO I guess it will be as challeging... Perhaps I can do it with the soldering iron.

Apart from this issue everything works as it should.

[Aliencomputres]

solder would never melt, guess I also need a way to pre heat the whole board first-use low melt solder !

[DynaxSC]

Regarding desoldering mosfets you need a high air temperature and preheater definitely. There is a post here from not long ago, there are more details.

Exchanging SIO is possible same way hotair + preaheater, but u need to isolate all plastics and electrolytic caps around very good with several layers of capton tape (I use it combined with tetra pack case material , to save the amount of capton tape). Anti heat gloves are helpful. Pay attention not to move smds around, better make a picture before. Some under pressure picker can help to get the chip off board. Be sure all pins are melted before removing the chip, its very easy to draw the tracks from the board. Especially such older boards have weak glue of the Cu pads/tracks with the board material. Todays boards are much more resistant.

You 858d is completely sufficient to do the job combined with a preheater. As a replacement for preheater u conditionally can use also an oldfashioned regulated electric cooker plate (not an inductive one) and handheld thermometer to set the temp., if u have such available. And, it's not necessary to preheat the whole board, 8-10 cm area around the mosfets is fully enough, so u don't need a very big preaheater. Preaheater set to 250-300 C, 3 cm distance, hotair 400-440 C, should do the job. Wait at least 5-10 minutes to let the preheater warm the board to ca 90-100 C on the top side, then apply hot air, still u will need to wait some time till tin is fluid. U can also loosely isolate the top of the board, eg with a sheet of paper or paper towel, then the warming up will be faster, and u might use lower temperatures, and less energy.

For mosfets you can do a trick to take them off, use a combination of hot air and a solder iron attached to the mosfet legs on the bigger pad with some good portion leaded tin and flux. The tin will mix with the unleaded tin and the melting temperature will go down making it easier to desolder the mosfet. However u need some magic "third hand" for the hot air gun to do this 😀. There are also special tins available with even lower melting temperature.

But, if you only want to check the mosfets for shorts, its better to take off the corresponding coils, or if possible disconnect one leg of them. The mosfets u can check then in-circuit.

Regarding the board necessarilly check the status of the Management Engine. You can do it with Intel CSME tools, or HWInfo or look in Device Manager, in the System Devices there must be a line like "Intel Management Engine Interface #1" or something similar (don't remember now exactly). Or just run the ME update tool from the support site and update or overwrite the ME, then u're sure. Do not mix it up with Chipset driver, thats something related, but not of interest.

Regarding the reflashing of the BIOS, it might not help always, as there are lot if parameters which are not updated during such update. If the issue is in these parameters the only way to repair this is programming a stock BIOS with a hw programmer. If that has helped, then the stock bios must be manually personalized with MAC address, UUID and serial no., or the NVRAM and Gbe regions must be transferred from the old BIOS to the stock BIOS. For ASUS BIOSes there is a handy tool to do it, called FD44.