Weird behavior when turning off the lights.

4hya said:

attached is a rough draft of the setup

Some questions:

• What country are you in? Is it 220v or 110v power grid?
• Is the lamp and the PC plugged into the same wall outlet or outlet strip?
• Are you using any wireless devices with this PC?
• What devices do you have externally connected (printers, external drives, etc.)? And where do they get their power from (wall outlet/power strip)?
• How old is the building you are living in (modern wiring or old wiring)?

Do you have a wireless mouse/keyboard or some other such peripheral connected to your PC? If so, what I think is happening when the light is being switched on is this. With a fluorescent light, when it is switched on, it usually flashes 2 or 3 times until it strikes and lights. Each time it flashes, a pulse of electromagnetic radiation is released, which, if it is not suppressed correctly, can cause interference to radios and other devices that utilise a wireless connection. My guess is that it is probably the starter that needs replacing, as its built-in suppressor might have failed.

If there is a problem with the wiring inside the light fixture and it is plugged into the same power source as any of the externally connected devices then it could be causing a momentary short circuit or electrical arc that is briefly taking the devices off line. This would be a bigger problem than the PC issue as any electrical arcing inside a fixture is a fire hazard.

You could isolate which device is disconnecting by systematically unplugging them one at a time and testing. If you find just one device that is doing this behavior you can isolate which power source is affected and narrow down the cause.

I don't see how an EM pulse would affect wired devices, unless the cables are unshielded. That is why I am more focused on the electrical power issue.