Question : Problem: Do I need to replace my PSU?

A small 100Watt light on the desk, plugged into the same circuit as 2 different PCs.  One of the PCs goes into
stand by or it shuts completely down when I turn on the light switch.   I have no other problems with this old reliable PC. 400 watts is more than enough for what I do on it.  And if the light is already on if I start the PC, It is just fine.

Do I need to  replace this PSU?

thank you in advance.

donnie616

Answer : Problem: Do I need to replace my PSU?

This will not be a shor but is likely to be caused by the small surge, probably surging enough to cause the PG line of the PSU to dip, thus causing the shutdown. I suspect the PSU. Worth checking the earth leakage on the light just in case.