XPS 8700 wont power on, can force start with PSU BIST

Question

Following a power outage, my 8700 wouldn’t boot up. I've run thru the various checks, hard reset, still not getting a clear indicator. I’m leaning toward a PSU over the Power button and motherboard. all removed items had no effect. appreciate any insights.

For the BIST, it will not power up on first contact, but will on the 2nd or 3rd touch with solid green light and system fans running at high speed. After unplugging and holding down button, then plugging back in, note the MB's aux power light is on but flickering in synch with a barely imperceptible ticking at a cadence of 5 to 6 ticks per second. still no response to power button no matter how long it’s pressed. hitting BIST again, noting first press. Second or third time will get it to green light and power fans AND the aux light is then solid no flicker or ticking after release.

Noted that when holding down the BIST the LED on power button glows solid amber. while holding down BIST to keep power, power button still has no effect.

This is where it gets interesting. Replaced cmos battery though original was fine, the bist will do the same no initial response then power system on third press with power button now glowing BLUE. keeping BIST pressed it will boot to bios screen. I set the time and save it, then it will boot to windows just fine ( must keep the PSU BIST held in during all this or it dies as soon as released). interestingly the system fan runs at normal speed when the power button is blue and system is botting normally, unlike other times.

The power button still has no effect to sleep or shutdown, like BIST held in bypasses it.

was able to select shut down from windows while holding the BIST and it exits windows, but while held in the power button went amber at shutdown and then the chassis fan kicked back up to high speed.

After releasing the BIST, still no response to power button.

hitting bist again, goes back to amber power button and high speed fans, no booting. it was reacting to initial press for a bit at that point.

To confirm, popped out cmos battery to see if it would replicate the previous bios reset behavior. Sure enough, while holding in BIST had a blue power button, normal fan speed, and able it to boot to windows after existing bios screen. So clearing the bios has an effect. But only way to keep it powered on is keeping the BIST held in.

What the forced power on (holding blis in) suggests to me is the cpu/ mb/ main drive / video card are likely fine.

But not sure why the cmos matters, if its an indicator of mb is having a problem, a wonky power button, or nothing at all. That click / flicker at first replug-in makes me think the psu is not able to supply power and keeps shutting down. I could swear in the past when it’s first plugged in, it would power up for a couple seconds before shutting down / standby.

btw, I've never had a problem with the power button over the last 11 years. I’m sure the power coming back on after the power failure could have finally fried something though it was on a surge protector. Appreciate input of how to tell which parts are the culprit.

Thanks

redxps630 · Accepted Answer

motherboard can POST notwithstanding some difficulties. that is good.

a failing psu often starts with increasingly difficult or finicky power button that needs to be pressed multiple times before pc would turn on. sometimes a bad psu just causes amber flash on power button and nothing else happens.

probably this is a good time to upgrade the psu or replace the stock one since you already spent a lot of time on the BIST and it has not returned to the former complete working status.

any reputable name brand 24/4 ATX psu would be good. stock psu is 460w. you need higher power psu if you plan to install a powerful gpu in the case. note 8700 is Intel 4th gen so the cpu may bottleneck more modern high power gpu. whether or not it is worth upgrading is individual user preference. If this is the only desktop you own and you have used for some time, you may like to continue using it understanding it is outdated yet good enough for you.

redxps630 · Answer

it would be easier for you to use a verified working 24/4 pin psu to test the motherboard. the BIST is just one test that may or may not always help.

any power rating test psu would work. you can borrow one from another desktop if available.

I also keep a direct 9 pin cable that can plug into the motherboard front panel to switch on power (after unplug stock front panel cable). at this point if I do this test is to see if a good psu can power on the mobo or not. remove all devices connected to mobo. only the 24/4 pin goes in and the power sw cable. if no cable then use a screwdriver to jump pin 6-8 which are pw sw+/-.

redxps630 · Answer

if the mobo is able to POST through whatever way you find but the normal pwr button does not work, then replace cmos batt a new one then clear cmos settings via motherboard jumper is the first thing to do.

erixgix · Answer

Appreciate the response @redxps630 , I wish I had another PSU, but I dont have any other desktops in the house unfortunately.

I did replace the CMOS batter with a new one and it was @ 3.3v. I cleared CMOS via jumper. It had no effect on response to the power button. Hitting the BIST on the PSU it would start up (again after the 3rd press vs first) and I found the power buttom LED is blue. I found I could release the BIST and it seem to keep running. Noticed the power button LED went out a couple times for a second, but does not seem to run to POST or be able to drive the video as the BIOS screen never came up.

However, the power button would turn it off. It wouldnt start it back up. And holding the BIST after that would do nothing and power button LED never came on.

The jumper reset and popping the batter out seem to accomplish similar things. After resetting again, and holding down the BIST, it would POST with the usual beep and then see the video pop up that CMOS was reset and it would boot into windows after continuing. This time, after shutting down thru windows and keeping the power going by holding the BIST in, the fans didnt speed back up on shutdown and hitting the now amber power button it actually turned it on.

My thought is, the PSU is not supplying sufficient power UNLESS that BIST button is held down based on it not being able to drive the video card and fully posting.

Does that sound like a reasonable conclusion and I should try a new PSU first? Was looking at an EVGA 750 N1, looks like it has the specs needed.

erixgix · Answer

Appreciate it!

No doubt outdated by todays standards. A couple years ago I was considering a new video card, but their cost and workarounds to try to install Windows 11 had me decide I’d replace it as prices came down eventually come down post chip shortages. Picked new laptops in the interim.

PSU ordered, will report back results.

erixgix · Answer

Success! Popped in the new PSU and everything is working perfectly.  We’ll see if we can coax another 11 years out of her ;)

XPS Desktops

XPS 8700 wont power on, can force start with PSU BIST

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