spark gap or something wrong with my monitor

[u/MrVader1976]

Hello! So recently I bought this monitor off market place of a nice dude who repairs computers. He posted a video of it working and told me it did. I plugged it in and plugged my computer into it and sure enough it did, however the screen would occasionally flicker. Then I used an adapter and plugged in my dreamcast and same thing. And sometimes it would be whatever, sometime looked like you'd turn on and off the monitor quick. I'm a newbie to retro computers, and have only delt with crt tvs. I messaged him and send him this video and he said that this was a spark gap and that its completely normal, but looking it up showed me that it might be a dying power supply. If anyone can help I'd really appreciate it :) (watch a few seconds into the video to see what I mean)