Okay. So, in 2022 I got a next to new in box Hansol Mazellan 701A. Opened but unused for some time. It's been absolutely fine until just a week or so ago, when in certain display modes ONLY it's started throbbing at a sort of rate of 2x/second. The picture bulges out as if it's going to maximum image size and then goes back to normal and repeats at that rate. It rectifies itself after a while, usually if you display a lot of colour at once, but the next time the mode switches to an affected mode, it behaves funny again, until you make it stabilise by having it display some sort of full screen image.

I normally have it at 800*600 16 bit colour for my Win9x box, but on startup it is in text mode and will be throbby until the Windows splash screen appears, then it will stabilise. Then when the desktop appears it will be normal. I have tested it in higher resolutions such at 1024*768 and up to 1280*1024 (its highest resolution) and it's okay in those. It's annoying because if I want to play a VGA DOS game on it, it'll throb for a few seconds then stabilise.

The affected resolutions are 320*200, 320*240, 640*480, 640*400. Basically anything VGA, if you will. Text modes are also affected. In text mode running something which I know displays a lot of characters, like dir /w/p in a busy folder, will stabilise it most of the time. Clearing the screen causes it to remain stable. It's only switching modes that triggers this.

I thought it might be magnetic interference as I have a pinball machine which has a big fuck-off transformer in the bottom of the cabinet, and which was plugged into the same power strip but I've put it on another socket now and it's still throbbing like that. Turning the monitor off and on doesn't help. Degaussing doesn't help.

Any idea what's wrong with it? There's no chance I'm opening it myself; I'm a clumsy oaf and I WILL flatline myself if I try.