Hi,

I've got several 240V to 12V 150W switching PSUs running circuits I've made. Most are working fine but today one of my circuits started resetting randomly.
After a long time checking various things I noticed that there seems to be a huge potential across the ground.

The PSU case and the 0V ground rail of my PCBs are all connected to earth through the 3-pin mains plug.
If I put a multimeter probe on the PSU case and the other probe on my PCB ground it measures over 1,300V.
With the mains disconnected I can confirm that there is definitely continuity between these points and with less resistance than my multimeter will measure.
Different points on the PCB get different readings. Points that are electrically further away from where the ground wire is connected read higher voltages.

Does anyone know what might be causing it and if it can be fixed? I've got quite a few of these PSUs now and I'm worried that everything will start failing and even become dangerous.