Pi 4 Output to Monitor

I’m trying to get my new Pi 4 going, it boots up but the output to the monitor is awful, rapidly-flickering horizontal lines on the monitor make it almost unusable.

I’ve tried altering the settings as per ‘config.txt (Raspberry Pi)’ in the wiki documentation but that’s as much as my technical expertise (such as it is) is able to do.
Pi 1 & Pi 3B work fine with my AOC monitor. I’ve been using a Samsung-b1930 file in Boot.Resources.Configure.Monitors but Pi 4 simply won’t recognise it at all.

Has anybody got any suggestions please?

the output to the monitor is awful, rapidly-flickering horizontal lines

I had a similar problem which I traced to a faulty HDMI cable.

Do you have another microHDMI-to-HDMI cable you can test with?

Well, well, well, I think you’ve got it Stuart – if I put very slight pressure on the cable the screen clears beautifully! The cable and the Pi 4 are brand new, not sure if it’s the cable or the socket on the Pi itself that’s at fault and I don’t have another cable to test but I’ll contact the vendor. Many thanks for solving my problem Stuart.

Had also problem with my Pi4: sometimes it showed a picture on the monitor, sometimes the monitor showed ‘no cable connected’.
After changing the HDMI- cable it works now.

Seems there are some (new) micro hdmi cable on market, with defect wiring.

A good way to guess: the thickness of the cable. If the cable is to thin or soft, then forget it.

My first Pi 4B on my 2560×1440 monitor and official micro HMDI cable, had a single flickery line at the top right of the display, and I found out much later that the second HDMI output doesn’t work, so there was obviously some issue with it. Its now connected to a full HD TV and doesn’t show any flicker on there. My latest 4B with the same cable has no problems with the monitor, and the second output also works.

So if it is within warranty, get in touch with the supplier, and request a replacement.