Computer won't boot with monitor connected

[HCHTech]

Weird intermittent issue with a 6-month old Ryzen 5 (integrated video) computer we built for a client. Dual monitors (an old one connected by VGA and a new one connected by HDMI. When computer is turned on, the new monitor is black and even it's power LED is off. Pushing the power button does not cause the LED to come on. Only the old monitor has video. It gives the normal bios lines, then Windows starts to boot with the spinning circle of dots, then goes black and hangs there until forced off.

If you disconnect the new monitor by unplugging the HDMI cable, it computer boots normally (and the new monitor's power LED comes on and it displays the expected "no signal" message. It booted ok 10 out of 10 times like this.

Plugging back in the new monitor, it will work sometimes (boot normally) and sometimes not (as described above).

Onsite, we tried a new surge strip and a new HDMI cable without success before we took the monitor back for further testing and potential warranty replacement. Here at the shop, if we hook the new monitor to a laptop, it works just fine with over a dozen reboots. We also hooked it to one of the bench machines as a primary monitor and it appears to work normally over a half-dozen reboots.

So, it's looking less like a bad monitor and more like a bad motherboard or power supply. We didn't really eliminate the computer when we were onsite yesterday because we didn't have a different HDMI monitor to test with. I expect we'll take one onsite on Monday to try that.

This is an unusual problem in my experience. Any suggestions?

 

[Larry Sabo]

Sounds like a power/ground problem with the computer. Perhaps take a multimeter with you and measure voltage between PC ground, mains grounds and monitor ground.

 

[PitterGrey]

I agree with the previous speaker. Most likely the lack of voltage to start the monitor when you turn on the computer.

 

[ComputerRepairTech]

I don't have an idea but just for clarification for the sake of the thread:
1. What happens if you try to boot with just the hdmi monitor connected without the vga plugged in at all?
2. What happens if you boot with just the vga monitor connected then later after its fully booted plug in the hdmi?

 

[HCHTech]

This appears to have been solved by replacing the surge strip. You guys were spot-on as usual. They had a "Monster" unit pos from Best Buy. We put in a new strip as a test at the same time we installed a loaner monitor. No problems for 4 days or so. Then we put the original monitor back in place and no problems reported so far. Likes all around!

 

[autigerfan33]

Troubleshooting with so many options and variables always sucks.