Monitor or PC issue?

Hello all,

I recently upgraded my rig, and purchased a new graphics card (ATI Sapphire R9 390) along with a 4k 28" monitor (iiyama B288UHSU). Unfortunately I'm now having big problems with the monitor.

Problem
- Video of the one of the first occurrences: https://www.youtube.com/watch?v=Ma3TH-YVlpI
- Monitor blinks/flashes with black horizontal lines, rapidly.
- Sometimes only a few small lines, sometimes enough black lines to cover the screen, and a few times It's turned entirely black.
- Occurs very intermittently. It tends to often occur after the PC has been turned off over night, but it also can occur after long periods of gaming.
- Sometimes the flashing will die down and stop after a short while, but sometimes this can take many hours. At the time of writing this, the monitor has the horizontal lines flashing now, and its been like that since the morning (10 hours roughly).

What I've tried
- I've got another 24" HD monitor attached to the GPU, and its working fine, and continues to, even when the new monitor is having issues.
- Whilst the flashing is going on, I've tried to switch cables (HDMI, DVI, different ports of DP)
- Plugged monitor into different wall socket, without and without a surge protector
- Tried different power cable
- When flashing is occurring, I've tried to disconnect and move the monitor without any PC connected (power cable connected only), and plug it into a wall socket within another room. After turning it on, it still shows the flashing of the horizontal lines, as I can see them when the iiyama logo splash screen pops up after powering it up.
- Tried switching refresh rate (60hz to 30hz).
- Tried plugging it into iMac whilst flashing is occurring (Display port). It continues to flash.

Info
- I recently had some problems with my old GPU, with it freezing my computer after gaming for a few hours. Thread for that is here. After replacing the GPU, the issue no longer occurs. One of the points that was brought up in the old thread was the possibility of the PSU being the culprit. Could this also have something to do with the monitor issue?

- I'm able to get a replacement monitor within 3 working days from iiyama, however, I'm afraid that because the issue is intermittent, they may not discover it, resulting in me having to possibly pay them extra? I'm assuming that what happens?

Spec
GPU: Sapphire R9 390
RAM: Corsair Vengeance 16gb
Mobo: Gigabyte Z77X-UP4 TH
PSU: Coolermaster 600w silent pro
Case: Fractal Design R5
CPU: i7 2600
Storage: Samsung SSD 850 Evo

If anyone has any suggestions, I'd really really really really really appreciate it.

Thanks for reading!
Jack

Firstly, what a well written request for help! States the problem, what you have done, and the results very concisely. So thank you for that. :)

I doubt it is the PSU as the problem seems confined to the monitor. I would suspect the monitor is faulty.

If you can take photos of the problem on two different computers, sending them to Iiyama when you report the fault should be sufficient to trigger an exchange.

If you are changing direct with the mfr, they may just write off the unit as investigating the fault and repairing probably costs more than the manufacturing price of the replacement.

If it's happening on multiple computers and on the monitor's own splash screen then it's an issue with the monitor. It could be something like interference but that's unlikely if it continues to do it in another room.