Monitor power cycling reboots computer?

[HCHTech]

I have custom workstation exhibiting this strange behavior.

Computer was new in October, 2015
Currently on Win-10 Pro with the Fall Creators update (was originally built w/Win10)
Asus MB, AMD FX-8370, 32GB RAM, Samsung Pro 850 500GB SSD (255GB Free space)
Antec EA 750 Platinum Power Supply
AMD Firepro W4300 Graphics card
Dual Viewsonic VG2753 monitors, each connected via Displayport
System is on a UPS (APC BR1000G)

User reports that they leave the computer running overnight, but turn both monitors off. In the morning, the computer looks normal, lights & fans running. When they turn the monitors on, the computer reboots. If, after the reboot, they power-cycle both monitors together, the computer will restart again. As long as they don't power-cycle the monitors, the computer runs fine all day.

I found a couple of Autodesk errors in the logs, but they are related to the help system and not coincident with the shutdowns. Nothing exciting in the system log.

I will probably have to wait until the weekend to physically get my hands on the computer, but I do have remote access.

Does this sound like a power problem? Graphics card? I've not run into this unusual symptom before - maybe someone else has?

 

[Larry Sabo]

Sounds like a household wiring and/or weak/failing PSU problem to me.

 

[phaZed]

There is a lot to check here. Could be the home wiring or PSU as @Larry Sabo suggests. Could be the UPS, it might not be able to handle the inrush current when the monitor's PSU kicks in. Check power issues first. Take the monitors off of UPS and plug 'em right to the wall, same effect? Try a different monitor, same effect?

If you get the same problems with the monitors on a 'different' circuit or off the UPS or with different monitors then I would be inclined to look at the video card or any 'excessive' VGA/video cabling.

There are filter caps and diodes on either side of the video cable (in the monitors and on the vid card) that filter out "ringing", noise and stored capacitance of the cable. If one of these is going bad then it is possible that the monitors turning on are causing a transient voltage spike that resets the video driver IC, causing a reboot.

 

[Markverhyden]

I agree it's probably a power issue. The monitors have a max power consumption of 45 watts. Which, usually, occurs during power up. So that's 90 watts plus the computer. Also, do they that have anything else plugged into the UPS? It's max output is 600 watts. I've seen perfectly normal UPS's cause problems when something gets powered up. But will run fine all day afterwards.

 

[PCS]

"Customers says" - dont believe their lies until you see it yourself.

Check power settings, is it going into a failed hibernate after x minutes of inactivity.

Does it actually reboot or does it fail to show any picture because of a failed sleep / suspend / hibernate and the only way to get it to work is power cycle?

Does it reboot when just the primary display is turned on?

If they turn the monitors off for an hour for dinner, whilst shopping.... and then turn them back on, does it then reboot or only in the morning after being on all night?

could it be as they lean across the desk to power on the monitors they somehow put pressure on a loose / bad cable and the PC reboots?

Good luck

 

[coffee]

To rule out the UPS I would just plug everything into straight power for a short period to see if the problem repeats. Then if it does I would do as @Markverhyden said and look a lot closer at the power supply.

There isnt a laser printer hooked to the ups is there?

 

[HCHTech]

I'll be going onsite to get a look at this directly on Friday. This customer is very tech savvy, and has already tried different monitors (same symptom), but I don't know if they have taken the UPS out and used direct power. For now, I told them to leave the monitors on until I can get a look. It sure sounds like power. Also, the failed hibernation thing seems to come up a lot with Windows 10, way more than I remember with Windows 7 or previous - I'll definitely check that out.

No desktop printers in this shop, only network printers - I've seen more than one problem caused by a laser printer in a UPS, though. I think they should put permanent stickers warning against this on all UPSes. (UPSs? UPS'?).

 

[Larry Sabo]

I'll be going onsite to get a look at this directly on Friday.

I'd suggest taking along a known-good PSU (power supply). That's what I was suggesting (not UPS - which I failed to note in your OP) might be at fault. I'd also check the MB for swollen/leaky caps.

 

[HCHTech]

I'd suggest taking along a known-good PSU

Yep - good call. Since they say it is 100% reproducible, we should be able to nail it down.

 

[Kirby]

As others have said, power would be the first thing to check. The wiring in my area tends to be pretty shoddy. The way household wiring is supposed to work is you have power, neutral and ground. Neutral and ground are NOT interchangeable. Each goes to its own bar in the breaker box. Now, in the breaker box, those two bars are connected with a wire and common sense says that means they're the same thing, but this is one of those instances where common sense is wrong. They should ONLY be connected by that single wire running between those two bars in the breaker box and nowhere else.

The first thing I would look at is the breaker box. There should be a bunch of white wires going to one bar and a bunch of bare wires going to the other. The black wires all go to individual breakers. There should be a wire running from the white bar to the bare bar. And the corresponding wires coming into the breaker box from the supply should be connected to those bars. For black and white it's the main incoming line. It has been a while, but I think the ground, the bare wire, is a separate wire not included in the incoming line. It should run to a grounding bar driven into the ground outside.

I would also spend about $3 and pick up a cheap wiring tester at your local hardware store. You just plug it in and the lights will tell you if any wires are crossed or not connected.

Finally, the latest Windows 10 update has been giving me some problems with sleep mode, at least on one computer. I had to change it to hibernate instead because it would take a couple of minutes to come out of sleep mode completely, when it didn't just randomly reboot. The computer (a new build) worked fine before doing the latest 1709 updates to Windows 10. Afterward I just could not get sleep mode to work properly. So maybe try switching to hibernate and see if that makes a difference.

 

[nlinecomputers]

Plugged into master switch of a UPS.

 

[HCHTech]

I ended up going onsite today. This is an office, btw, not a home. They have a server & about 20 workstations. The problem workstation is still plugged directly into a surge strip, so the UPS was not the problem. They had 3 identical monitors on the system, all attached to the card via HDMI. The system is set to never sleep or hibernate. The system was running, and I could power off and then on both the secondary and tertiary monitors without impact. When you power them back on, all three screens go blank and then come back on. This is the Windows bit identifying the new monitor and placing it in the mix. When I power off the primary monitor, however, turning it back on indeed causes a reboot. Oddly enough, if I switch the monitor definition so that a different monitor is the primary, then the problem moves to that monitor. It reboots only when the primary monitor is powered off, then back on again. I check and they are not on the latest video driver, but one that was released in July, so still pretty current.

After a look around inside the case (the motherboard has all solid caps, and nothing looks awry), I put in the replacement power supply. Unfortunately, I'm apparently an unlucky guy today as the system won't even power on with the new power supply. I check to make sure I didn't unhook anything, but no dice. The power led on the motherboard lights up, but pressing the power button does nothing. No fans spin up or anything.

I decide not to waste time trying to troubleshoot the new power supply and re-install the old one. I also move the video card from the primary PCI slot to the secondary one (the one farthest away from the CPU). I power it back up and the rebooting does not return. I turned all of the monitors off and back on about a dozen times each without a reboot.

So....it appears that the problem is related to the primary PCI slot on the motherboard. I suspect that I'll be seeing this system again soon, but for now at least, it appears the problem has been resolved. I'm ordering an exact replacement motherboard and power supply to have on the shelf for when they call back.

I asked them to use it normally for a day and if the problem doesn't return, then put the UPS back in place. We'll see how it goes.

 

[PCS]

I guess it could also have been the graphics card / reseating may have solved. would have been good to see if moving it back to the original slot continued the issue.